WO1995010484A1

WO1995010484A1 - Process for decreasing chlorine content in chlorinated hydrocarbons

Info

Publication number: WO1995010484A1
Application number: PCT/US1994/011697
Authority: WO
Inventors: Jeffrey Schwartz; Yumin Liu
Original assignee: The Trustees Of Princeton University
Priority date: 1993-10-14
Filing date: 1994-10-14
Publication date: 1995-04-20
Also published as: BR9407819A; NO961482L; AU7979994A; EP0723525A4; EP0723525A1; CA2173970A1; KR960704807A; NO961482D0; JPH09503789A; CZ108296A3; SG49250A1; IL111277A0

Abstract

The chlorine or halide content in a chlorinated hydrocarbon or halogenated aromatic hydrocarbon in an environment which admits to the presence of air and moisture can be reduced by bringing the chlorinated hydrocarbon or halogenated aromatic hydrocarbon into contact with a reagent which comprises (i) a complex of a substantially nontoxic metal having at least two oxidation states and (ii) a reducing agent which reductively returns the complex from its second oxidation step to its first oxidation stage. A representative embodiment involves bis-(θ5-cyclopentadienyl)titanium dichloride and sodium tetrahydridoborate. Optionally, the reaction is conducted in the presence of an aliphatic or aromatic amine, optionally in the presence of an inert organic solvent.

Description

PROCESS FOR DECREASING CHLORINE CONTENT

IN CHLORINATED HYDROCARBONS

Background of the Invention

This invention pertains to a process for decreasing the content of chlorine in chlorinated hydrocarbons, and for reducing aromatic halide content in haiogenated aromatic hydrocarbons.

Various chlorinated hydrocarbons such as polychlorinated biphenyls, tetrachloroethylene, trichloroethylene, 1,2,3-trichloropropane, polychlorinated naphthalene, chlorine containing fluorocarbons ("Freons"), polychlorinated cyclodienes such as aldrin and dieldrin, polychlorinated bicycloalkanes such as mirex etc., are recognized environmental contaminants. Numerous chemical, physical, and microbiological methods for eliminating these presently are under investigation. While microbiological techniques are useful in bioremediation of many contaminants, such techniques have not proven satisfactory for highly chlorinated, products such as those containing four or more chlorine atoms; see e.g., Hill et al . , Appl . Biochem. Biotechnol . , 20/21, 233 (1989) and Waid, "PCBs and the Environment, " Vol. II, 78, CRC Press, Boca Raton, Florida.

Various chemical approaches have been investigated but again it appears the greater the number of chlorine atoms in a target contaminant, the more difficult the dechlorination. Moreover systems which appear to be useful in the controlled environment of the laboratory encounter unexpected difficulties when an attempt is made to adapt the system to the competitive and ambient environment where such highly chlorinated products pose the greatest problem.

Wilwerding, U.S. Patent No. 4,931,167, describes the degradation of polychlorinated biphenyls in a non-aqueous medium using anhydrous metal halides such as the chlorides and bromides of aluminum, titanium, tin, iron, etc. Imamura et al . , U.S. Patent No. 4,957,717, describe the disposal of organic compounds by burning them in contact with a catalyst of a composite oxides such as titanium-silicon composite oxides and titanium-silicon-zirconium composite oxides.

Anderson et al . , U.S. Patent No. 5,035,784, describe degradation of polychlorinated biphenyls by photocatalysis by ultraviolet light utilizing porous titanium ceramic membranes. Meunier, J. Organometal . Chem , 204 (1981), 345-346 describes the selective reduction of aromatic iodides with sodium borohydride activated by a catalytic amount of bis- (η⁵-cyclopentadienyl) titanium dichloride or η⁵-cyclopentadi-enyltitanium trichloride in dimethylformamide and in the presence of air. Aromatic chlorine atoms were not affected.

Kozloski, J. Chromatogr. , 318 (1985) 211-219 describes partial catalytic dechlorination of polychlorinated biphenyls with sodium borohydride and nickel boride catalyst. Stojkovski et al . , J. Chem. Tech. Biotechnol . 1990. 51, 407-417, describe dechlorination of polychlorinated biphenyls and polychlorinated naphthalenes with nickel chloride/sodium borohydride catalysts. In a companion paper, J. Chejn. Tech. Biotechnol . , 1991, 51, 419-431, Stojkovski et al . extend the use of this nickel chloride/sodium borohydride system to chlorinated cyclodiene and bicyclic insecticides.

Bosin et al . , Tetrahedron Letters , 4699-4650 (1973) report on the reduction of aryl halides with a sodium borohydride-palladium system.

Carfagna et al . , J. Mol . Cat . 57 (1989) 23-28, describe the use of magnesium hydride and various metal halides in the reduction of aryl monohalides.

Rolla, J. Org. Chem. , 46, 3909-3911 (1981) reports on the use of sodium borohydride to reduce a variety of haiogenated hydrocarbons using hexadecyltributylphosphonium bromide as a catalyst.

Bergbreiter et al . , J. Org. Chem. , 54, 5138-5141 (1S39) describe the use of tin catalyst attached to soluble polyethylene and polystyrene for use in alkyl halide reductions. Loubinoux et al . , Tetrahedron Letters , 3951-3954 (1977) report on the activation of sodium hydride by certain metal salts in the reduction of various organic halides.

Tabaei et al., Tetrahedron Letters , 2727-2730 (1991) describe the use of polyethylene glycol or tetraethylene glycol in the metal catalyzed reduction of chlorinated hydrocarbons with sodium borohydride or sodium alkoxyborohydride.

DETAILED DISCLOSURE

The present invention involves a method for chemically reducing the overall chlorine or halide content in compounds, generally but not necessarily chlorinated hydrocarbons or haiogenated aromatic hydrocarbons. The process is characterized by the ability to operate economically in a mixed ambient environment, notably in the presence of water and oxygen found in air. Although not so limited, it has particular value as a pretreatment to microbiological degradation of chlorinated hydrocarbons in that highly chlorinated compounds which are resistant to bioremediation can be converted to compounds having a lower content of chlorine, thereby being more susceptible to microbiological degradation. Broadly the process involves bringing the chlorinated hydrocarbon into contact with a dechlorination reagent of the type described herein. Heat can be applied to accelerate the reaction. By conducting the reaction in the presence of an aliphatic or aromatic amine, the scope of the reaction can be expanded to other haiogenated compounds and a greater degree of dehalogenation can be achieved. The dechlorination reagent contains two principal components.

The first component of the dechlorination reagent is a metal complex having at least two oxidation states. In a first, lower oxidation state, the complex is operable to transfer an electron to the chlorinated hydrocarbon and thereby reductively eliminate a chlorine atom from the chlorinated hydrocarbon. In transferring the electron, the complex assumes its second, higher oxidation state; i.e., it is oxidized.

The second component of the reagent is a reducing agent operable to reductively return the complex from its second oxidation step to its first oxidation stage; i . e. , to reduce the complex back to its original oxidation state.

It will be appreciated that the net result of these two reactions is the consumption of the second component and the regeneration of the first component. Consequently the first component effectively acts as a catalyst in the sense that while it participates in the reduction of chlorinated hydrocarbon, it is returned to its original oxidation state in which it can enter into a further reaction. Consequently the amount of the first component which must be introduced into the environment is relatively small. Moreover while these two components are referred to herein as a reagent or system in that they co-act, in use they can be introduced either in pre-formed combination or separately. It is critical to the process, however, that both components operate under the ambient conditions of the environment and do so without causing further contamination. For example, complexes containing nickel may be technically effective as the first component in reducing chlorinated hydrocarbon but are unsuitable because the nickel of the complex thus introduced into the environment itself is toxic. Similarly sodium hydride and lithium aluminum hydride in theory are effective as the second component but both react with water and thus are unsuitable, being unstable in a mixed environment.

The first component will contain a substantially nontoxic transition metal of Group 4 or 5 (IVa or Va) and will form a complex with multidentate and unidentate organic and inorganic ligands. Particularly preferred are titanium and zirconium compounds including benzoates, chlorides, salen complexes, prophyrins, tris(pyrazoyl) borates, poly (alkylamino) complexes, poly (alkylamino) chelates, poly(thioalkyl) complexes, poly (thioalkyl) chelates, and mixtures thereof. One highly effective subclass are the organometallic complexes of titanium and zirconium such asbis-(η⁵-cyclopentadienyl)titanium dichloride, bis-(η -cyclopentadienyl)zirconium dichloride, η⁵-cyclopentadienylzirconium trichloride, and η⁵-cyclopentadienyltitanium trichloride. Particularly useful in view of its currently relatively low cost and performance is bis-(η⁵-cyclopentadienyl)titanium dichloride, also known as titanocene dichloride.

The second component will be a hydridoborate, typically a polyhydridoborate, such as an alkali metal or ammonium salt of a tetrahydridoborate, thiocyanatotrihydridoborate, cyanotrihydridoborate, acyloxytridridoborate, octahydridotrihydridoborate, trialkylhydridoborate, acetanilidotrihydridoborate, trialkoxyhydridoborate, and metal chelates thereof. Particularly useful in view of its current relatively low cost and performance is sodium tetrahydrido borate .

In the absence of the first component, the hydridoborate may show some dechlorination properties but the rate is far slower and the range of chlorinated compounds in which such dechlorination is seen is far more limited than when the metal complex is present.

The amine which is added can be any aliphatic amine such as trimethylamine, triethylamine, dimethylethylamine, etc. , an aromatic amine such as N,N-dimethylaniline, N,N-dimethylnaphthylamine, etc. , or an aromatic or nonaromatic heterocyclic amine such as pyridine, 1-methylimidazole, quinoline, piperidine, etc. Although primary and secondary amines can be employed, preferably the amine is a tertiary amine. Generally a molar excess of the amine is employed. While other non-amine bases such as sodium methoxide appear to have a slight effect in accelerating the underlying reaction, this is by no means as dramatic as that observed upon addition of an amine.

The target polychlorinated hydrocarbons, particularly polychlorinated aromatic compounds, often present a complex mixture of cogeners. In the case of PCB's for example, the cogeners present can number in the hundreds. It thus is convenient to study the use of the present reagent with substantially pure chlorinated compounds. As shown below, the usefulness of the reagent in reducing the chlorine content of pure compounds also is seen in mixtures of chlorinated compounds.

The haiogenated hydrocarbons on which the process is operable include haiogenated aromatic, aliphatic, and olefinic compounds such as polychlorinated biphenyls (PCB's), tetrachloroethylene, trichloroethylene, 1,2,3-trichloropropane, and the like. Other functional groups such as oxo groups (ketones, carboxylic acids and esters), amino groups (including secondary and tertiary amino groups), nitro groups and the like also can be present in the compound or compounds being treated. Such if such a groups, if susceptible to reduction, may be reduced in the course of the process. Such products generally are equally or more amenable to bioremediation.

It will be appreciated that upon removal of one chlorine atom from a given polychlorinated compound, a further chlorine atom can and will be removed from the product by repetition of the reaction and in fact typically starting with a highly chlorinated compound a series of different products, each having a fewer but different number of chlorine atoms per molecule, will be produced. For example, beginning with hexachlorobenzene, the first product will be pentachlorobenzene. The pentachlorobenzene thus formed in turn will be converted to 1,2,3,4-tetrachlorobenzene and 1,2,4,5-tetrachlorobenzene. 1,2,4,5-Tetrachlorobenzene produces 1,2,4-trichlorobenzene. Since these reactions proceed concurrently, a plurality of products generally are formed but the net result of the process will be a reduction in the overall chlorine content of the chlorinated hydrocarbon.

The reactive intermediate generated from the chlorinated hydrocarbon can react with other organic materials present in the rection area. For example if the treatment of 1,2,4,5-tetrachlorobenzene is conducted in the presence of dimethylformamide as a solvent, the products can include not only 1,2,4-trichlorobenzene but also N,N-dimethyl-2,4,5-trichloroaniline. Similarly, when the process is conducted with 1,3,5-trichlorobenzene, both N,N-dimethyl-3,5-dichloroaniline and 1,3-dichlorobenzene will be produced. Whether this involves a nucleophilic mechanism or free radical mechanism is not known but the products so fcrmed are in any event more amenable to bioremediation by reason of the net reduction in the number of chlorine atoms. Moreover, the present reagent appears to operate effectively not only on highly chlorinated compounds and but also on compounds containing only a few chlorine atoms.

The reaction to which an amine is added can be conducted in a variety of inert organic solvents such as diglyme, triglyme, bis-(2-ethoxyethyl) ether, tetrahydrofuran, dimethylsulfoxide, dimethylformamide, ethylene glycol dimethyl ether and the like. Particularly preferred are ethers such as diglyme. The following examples will serve to further exemplify the present invention without being construed as being a limitation thereof. The designations used herein for the metal complexes used are as follows:

Metallic Complex Designation oxo (tetraphenylporphyrinato) titanium oxide . . . . . . . . . . . A .

η⁵-cyclopentadienyltitamum trichloride . . . . . . . . . . . . . . B

(salen) titanium dichloride . . . . . . . . . . . . . . . . . . . . . . . . . . C titanium trichloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dbis- ( η⁵-cyclopentadienyl ) titanium dichloride . . . . . . . . . E titanium tetrapropoxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F oxobis (acetylacetonato) titanium . . . . . . . . . . . . . . . . . . . . . G titanium boride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H

{tris[3,5-dimethylpyrazoyl]borate}

titanium trichloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I bis- (η⁵-cyclopentadienyl) zirconium dichloride . . . . . .. . J

EXAMPLE 1

A. Without Catalyst

A mixture of 2 mmol of hexachlorobenzene and 8 mmol of sodium tetrahydridoborate in 10 mL of dimethylformamide was heated with stirring for 36 hours at 88°C in an air atmosphere in a reaction vessel equipped with a condenser. At the end of this time, water was added and the mixture extracted with ether. Analysis of the ethereal extract by gas chromatography (flame ionization detector) and by gas chromatography/mass spectrography indicated the following composition:

Compound mmol tetrachlorobenzenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0. 475

N, N-dimethyltetrachloroanilines . . . . . . . . . . . . . . . . . . . . . 0. 482

N, N-dimethyltrichloroanilines . . . . . . . . . . . . . . . . . . . . . . . 0. 363 trichlorooenzenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 107

B. With Catalyst

By following substantially the same procedure as that set forth in Part A with 1.87 mmol of hexachlorobenzene and 7.88 mmol of sodium tetrahydridoborate in 10 mL of dimethyl-formamide with heating at 85°C but adding 0.19 mmol of metal complex I, the following reaction composition was obtained after 11 hours.

Compound mmol tetrachlorobenzenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.502

N,N-dimethyltetrachloroanilines . . . . . . . . . . . . . . . . . . . . .0.682

N,N-dimethyltrichloroanilines . . . . . . . . . . . . . . . . . . . . . . .0.393 trichlorobenzenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.069

EXAMPLE 2

Following the procedure of Example 1, Part B, 2 mmol of hexachlorobenzene, 8 mmol of sodium tetrahydridoborate, and 0.2 mmol of each of metal complexes A, B, C, D, and E were heated in 10 mL of dimethylformamide.

The conditions and results are summarized on Table I. Table I

Complex Temp. Time C₆Cl₃H₃ C₆Cl₄H₂ C₆Cl₃H₂N(CH₃)₂ C₆CL₄HN(CH₃)₂ C₆Cl₃H₂OH C₆Cl₅H

ºC Hours mmol mmol mmol mmol mmol mmol

A 80 18 0.045 0.929 0 0.033 0.150 0.182

B 79 18 0.048 1.033 0 0.109 0 0.308

C 70 18 0.019 0.558 0.047 0.528 0 0.179

D 84 18 0.081 0.819 0.143 0.416 0 0.174

E 72 18 0.018 0.740 0 0.018 0.024 0.177

None 72 36 0.107 0.475 0.363 0.482 0 0

EXAMPLE 3

A. Without Catalyst

A mixture of 2 mmol of pentachlorobenzene and 8 mmol of sodium tetrahydridoborate in 10 mL of dimethylformamide was heated with stirring for 1.1 hours at 85°C in an air atmosphere in a reaction vessel equipped with a condenser. At the end of this time, water was added and the mixture extracted with ether. Analysis of the ethereal extract by gas chromatography (flame ionization detector) and by gas chromatography/mass spectrography indicated the following composition:

Compound mmol pentachlorobenzene (starting compound) . . . . . . . . . . . . . . .1.086

1,2,4,5-tetrachlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . .0.56 1,2,3,4-tetrachlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . .0.063

B. With Catalyst

By following substantially the same procedure as that set forth in Part A but adding 0.2 mmol of metal complex E, the following reaction composition was obtained after 1.1 hours.

Compound mmol pentachlorobenzene (starting compound) . . . . . . . . . . . . . . 0.732 1,2,4,5-tetrachlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . .0.566

1,2,3,4-tetrachlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . .0.077 1,2,4-trichlorobenzenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.013

EXAMPLE 4

A. Without Catalyst

A mixture of 1 mmol of 1,2,4,5-tetrachlorobenzene and 4 mmol of sodium tetrahydridoborate in 10 mL of dimethylformamide was heated with stirring for 3.5 hours at 95°C in an air atmosphere in a reaction vessel equipped with a condenser. The reaction mixture, extracted and analyzed as described above, had the following composition:

Compound mmol 1 , 2 , 4 , 5-tetrachlorobenzene (starting compound) . . . . . .. 0. 84

1,2,4-trichlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.11

N,N-dimethyl-2 , 4 , 5-trichloroaniline . . . . . . . . . . . . . . . . .. 0.05

B. With Catalyst

By following substantially the same procedure as that set forth in Part A but adding 0.2 mmol of metal complex E, the following reaction composition was obtained after 3.5 hours.

Compound mmol

1,2,4,5-tetrachlorobenzene (starting compound) . . . . . ..0.12 trichlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.45

N, N-dimethyl-2 , 4 , 5-trichloroaniline . . . . . . . . . . . . . . .... 0. 43

EXAMPLE 5

Following the procedure of Example 4, Part B, 1 mmol of 1,2,4,5-tetrachlorobenzene, 4 mmol of sodium tetrahydridoborate, and the indicated amount of each of metal complexes E, F, G, H, and J were heated in dimethylformamide.

The conditions and results are summarized on Table II.

Table II

Complex Temp. Time Metal Complex C₆Cl₃H₃ ^a C₆Cl₃H₂N(CH₃)₂ ^b C₆Cl₄H₂ (Recovered)

ºC hours mmol mmol mmol mmol

E 95 3.5 0.1 0.45 0.43 0.12

E 95 1.8 0.2 0.42 0.42 0.16

F 95 3.5 0.1 0.33 0.38 0.29

J 95 1.8 0.1 0.30 0.56 0.14

- 95 3.5 - 0.11 0.05 0.84 a = 1,2,4-trichlorobenzene

b = N,N-dimethyl-2,4,5-trichloroaniline

EXAMPLE 6

Following the procedure of Example 4, Part B, 2 mmol of 1,2,4,5-tetrachlorobenzene, 8 mmol of sodium tetrahydridoborate, and the indicated amount of each of metal complexes A, B, D, C, and I were heated in dimethylformamide.

The conditions and results are summarized on Table III.

Table III

Complex Temp. Time Metal Complex C₆Cl₃H₃ ^a C₆Cl₃H₂N(CH₃)₂b C₆Cl₄H₂ (Recovered)

ºC hours mmol mmol mmol mmol

A 75 5.8 0.2 0.06 0.06 1.88

B 75 5.8 0.2 0.56 1.24 0.20

C 75 5.8 0.2 0.48 1.26 0.26

D 75 5.8 0.2 0.48 1.36 0.16

I 75 5.8 0.2 0.48 1.30 0.22 a - 1,2,4-trichlorobenzene

b = N,N-dimethyl-2,4,5-trichloroaniline

EXAMPLE 7

A. Without Catalyst

A mixture of 8 mmol of sodium tetrahydridoborate and 2 mmol of 1,4-dichlorobenzene in 10 mL of dimethylformamide was heated with stirring for 6.5 hours at 80°C in an air atmosphere in a reaction vessel equipped with a condenser. Upon extraction and analysis as described above, only starting material could be detected.

B. With Catalyst

By following substantially the same procedure as that set forth in Part A but adding 0.2 mmol of metal complex E, the following reaction composition was obtained after 6.5 hours.

Compound mmol 1,4-dichlorobenzene (starting compound) . . . . . . . . . . ... .1.96 chlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .0.04

EXAMPLE 8

1,2,3-Trichloropropane was treated with sodium tetrahydridoborate and metal complex E at 100°C for 1 hour in substantially the fashion described above. Gas chromatography/mass spectrography indicated no 1,2,3-trichloropropane remained in the reaction mixture.

EXAMPLE 9

Treating tetrachloroethylene (325 mg) with sodium tetrahydridoborate and metal complex E at 93°C for 3 hours and 20 min. in substantially the fashion described above converted 98% of starting material to trimethylamine, 1,1-dichloroethylene, 1,2-dichloroethylene, and N,N-dimethylaminomethanol as determined by gas chromatography/mass spec trography.

EXAMPLE 10

Five and one-half parts by weight of a commercial mixture of polychlorinated biphenyls (Aroclor 1248) were extracted with ether and the ether then evaporated in vacuo . To the residue were added 45 parts by weight of sodium tetrahydridoborate, 25 parts by weight of metal complex E, and 1 part by volume of dimethylformamide. The mixture was heated at 92°C. After one hour the mixture became viscous and an additional 0.5 part by volume of dimethylformamide was added. After an additional 17 hours of heating (a total of 18 hours), the reaction products were extracted with ether and passed through a short column of silica gel to remove the residual metal complex. Upon analysis, the reaction product contained about 25% (1.36 parts by weight) of polychlorinated biphenyls, indicating a 75% reduction.

The results of utilization of the foregoing procedure with metal catalysts A, B, C, D, E, H, I, and J are shown on Table IV.

Table IV

Complex Amount NaBH⁴ Temp. Time PCB (Before) PCB (After) Dechlorination mq mq ºC hours mg mg

A 17.6 12.6 100 18 3.3 0.76 77%

B 9.0 10.6 100 18 3.3 1.39 58%

C 12.5 12.4 100 18 3.3 2.37 28%

D 7.0 10.5 100 18 3.3 1.24 62%

E 8.0 13.6 100 18 3.3 0.28 92%

H 145.0 45.0 92 18 7.0 4.60 34%

I 9.9 12.9 100 18 3.3 1.79 46%

J 22.0 45.0 92 18 7.5 2.07 72%

EXAMPLE 11

A commercial mixture of polychlorinated biphenyls (Aroclor 1248, 3.3 parts by weight) was extracted with ether and the ether then evaporated in vacua . To the residue were added 21 parts by weight of bis-(η⁵-cyclopentadienyl)-titanium tetrahydridoborate and 1 part by volume of dimeth- ylformamide. The mixture was heated at 100°C. After a total of 18 hours, the reaction products were extracted with ether and passed through a short column of silica gel to remove the residual metal complex. Upon analysis, the reaction product contained about 40% (1.31 parts by weight) of polychlorinated biphenyls, indicating a 60% dechlorination.

The foregoing example demonstrates that the metal complex and the hydridoborate can be combined in the same molecule to achieve the desired result, requiring however a stoichiometric amount of the reagent. Although this confirms the working premise of the invention, it introduces metal in excess of that which is required in order to effectively lower chlorine content with hydridoborate and a catalytic amount of the metal complex.

EXAMPLE 12

A mixture of 0.3 mmol of metal complex E and 30.0 mmol of sodium tetrahydridoborate in 30 mL of dimethylformamide was heated with stirring for 1 hour at 92°C in an air atmosphere in a reaction vessel equipped with a condenser. The reaction product was filtered through a Celite plug and a fine glass frit to produce the dehalogenation reagent as a dark brown solution.

If 1,2,4,5-tetrachlorobenzene is added to this solution and the mixture then heating at 92°C, it is reduced to a level below 10% in about 60-65 minutes with the formation of 1, 2 , 4-trichlorobenzene and N,N-dimethyl-2,4,5-trichloroaniline (as determined by gas chromatography/mass spectrography).

EXAMPLE 13 A reaction vessel equipped with a condenser is charged with approximately 5 g of soil contaminated with polychlorinated biphenyls. A portion of sodium tetrahydridoborate, and 150 mg of metal complex E in dimethylformamide are added and the mixture is heated with stirring at 100°C in an air atmosphere in a reaction vessel. After 30 minutes, additional sodium tetrahydridoborate and metal complex E are added. (Any material on the walls of the vessel can be washed off with dimethylformamide.) After another 20 minutes, additional sodium tetrahydridoborate is added and the reaction mixture is stirred for 18 hours. The reaction can be quenched with water and the reaction mixture exhaustively extracted with ether (to insure partition of all chlorinated biphenyls). Analysis of the ethereal extracts is performed by gas chromatograph and compared against the untreated contaminated soils.

The results of utilization of the foregoing procedure with samples of soil contaminated with polychlorinated biphenyls produced are shown on Table V.

Table V

Soil Sample Weight NaBH₄ PCB (Before) PCB (After) Dechlorination g mg mg mg

I 5.1 870 47.1 34.14 28%

II 5.0 930 47.1 30.00 36%

III 5.1 880 1.33 0.88 34%

Approximately 2 to 5 g of the soil sample are placed into a 20 mL serum vial, the sample is amended with an equal volume mL/g of distilled water and to this mixture are added 10 mL of diethyl ether. The vial is sealed and shaken on a rotary shaker for 24 hours. The ether phase then is transferred to a 1.5 mL serum vial for analysis. (If needed, the original ether extract can be either concentrated or diluted to ensure accurate sample analysis.)

Samples containing interfering substances are cleaned using appropriate methods. Non-PCB oils (hydraulic fluids, mineral oil, etc.) are removed by passing the extracts through a conditioned magnesium silicate matrix. The retained PCBs are eluted from the matrix with hexane and the wash is either diluted or concentrated for GC analysis. Samples which are found to contain elemental sulfur are cleaned by combining 2 mL of the sample extract with 1 mL of reagent containing 3.39 g of tetrabutylammonium hydrogen sulfate and 25 g sodium sulfite in 100 mL of water and 1 mL of 2-propanol. After mixing for five minutes, an additional 3 mL of water are added to remove the alcohol and reagent. The ethereal layer is transferred to a gas chromatograph equipped with an electron capture detector (300°C), a split/splitless capillary injector (300°C), and a fused silica column (length = 30m, inner diameter = 0.25 mm) coated with a 0.25 μm bonded liquid phase of polydimethylsiloxane. The column is temperature programmed from 160°C to 200°C at 2°C/min/no hold time to 240°C at 8°C/min and held for 10 minutes. The gas flow rates are set as follows: carrier gas (helium) at 23 cm/sec (067 mL/min); make-up gas (nitrogen) at 33 mL/min; and a split ratio of 16.

Chromatograms of the samples are integrated on a peak-by-peak basis and the area of each peak is normalized with respect to standard mixtures of known PCB composition.

Figure 1 is a gas chromatrogram of soil before treatment from which Samples I and II were taken. The plotting attenuation is 40. The retention time is a function of the degree of chlorination. Figures 1A and 1B are gas chromatograms of Samples I and II, respectively, after dechlorination as described above. The plotting attenuation for Figure 1A is 21; that for Figure 1B is 31.

In addition to an overall decrease in chlorine content in both samples, it will be observed that the population of heavily chlorinated components (a retention time of about 30 minutes or more) has been greatly reduced, the heavily chlorinated products having been converted to more lightly chlorinated products.

Figure 2 is a gas chromatogram of Sample III before treatment. The plotting attenuation is 56. Figure 2A is the chromatrogram (plotting attenuation of 11) after dechlorination as described above. Again a shift in population from highly chlorinated compounds (retention time above about 30 minutes) to more lightly chlorinated compounds accompanies a reduction in overall chlorine content.

EXAMPLE 14

A flask equipped with a magnetic stir bar and a water cooled condenser with an oil bubbler was charged with sodium tetrahydridoborate (568 mg, 15.0 mmol), bis-(η⁵-cyclopentadienyl) titanium dichloride (374 mg, 1.5 mmol), Aroclor^® 1248 (1095 mg, 3.75 mmol based on an average molecular formula: C₁₂H₆Cl₄), and N,N-dimethylacetamide (DMA; 15.0 mL). The flask was heated at 75°C for 10 hours and at 105°C for 4.25 hours. The reaction mixture was quenched with water (30 mL) and extracted with ethyl acetate (50 mL). The ethyl acetate solution was filtered through a short column of silica gel and washed with ethyl acetate. The resulting filtrate was analyzed by GC and compared with standard Aroclor^® 1248. Substantial reduction to mono-, di-, and trichloro PCBs was noted. No PCB containing more than three chlorine atoms per congener as present. EXAMPLE 15

A flask equipped with a magnetic stir bar and a water cooled condenser with an oil bubbler was charged with

1,2,4,5-tetrachlorobenzene (648 mg, 3.0 mmol), sodium tetrahydridoborate (1135 mg, 30.0 mmol), bis-(η⁵-cyclopentadienyl) titanium dichloride (75 mg, 0.3 mmol), and 1-methyl- 2-pyrrolidine (NMP; 30.0 mL). The reaction mixture was heated at 96°C in an oil bath. After 4.25 hours, lithium chloride (1.09 g, 30.0 mmol) was added. Aliquots were withdrawn by syringe, quenched with water, and extracted with diethyl ether. The ether layer was analyzed with the results shown in the following table. Only trichlorobenzene was produced.

TIME (min) C₆Cl₄H₂ C₆Cl₃H

1 34.0 0.924 0.076

2 84.0 0.829 0.171

3 218.0 0.642 0.358

4* 254.0 0.605 0.395

5 279.0 0.517 0.483

6 331.0 0.355 0.645

7 402.0 0.248 0.752

* lithium chloride added

EXAMPLE 16

A flask equipped with a magnetic stir bar and a water cooled condenser with an oil bubbler was charged with 1,2,4,5-tetrachlorobenzene (648 mg, 3.0 mmol), sodium tetrahydridoborate (1135 mg, 30.0 mmol), bis-(η⁵-cyclopentadienyl) titanium dichloride (75 mg, 0.3 mmol), and dimethyl- sulfoxide (30.0 mL). The reaction mixture was heated at 92°C in an oil bath. Aliquots were withdrawn by syringe, quenched with water, and extracted with diethyl ether. The ether layer was analyzed with the results shown in the following table. Only trichlorobenzene was produced. TIME (min) C₆Cl₃H₃ C₆Cl₄H₂ ln(C₆Cl₄H₂)

1 85.000 0.069 0.931 -0.071

2 180.000 0.128 0.872 -0.137

3 285.000 0.174 0.826 -0.191

4 340.000 0.205 0.795 -0.229

5 426.000 0.246 0.754 -0.282

EXAMPLE 17

A flask equipped with a magnetic stir bar and a water cooled condenser with an oil bubbler was charged with 1,2,4,5-tetrachlorobenzene (648 mg, 3.0 mmol), sodium tetrahydridoborate (1135 mg, 30.0 mmol), bis-(η⁵-cyclopentadienyl) titanium dichloride (75 mg, 0.3 mmol), and N,N-dimethylacetamide (30.0 mL). The reaction mixture was heated at 95°C in an oil bath. Aliquots were withdrawn by syringe, quenched with water, and extracted with diethyl ether. The ether layer was analyzed with the results shown in the following table. Only trichlorobenzene was produced and <1% of N,N-dimethyl-2,4,5-trichloroaniline were detected.

TIME (min) C₆Cl₄H₂ ln(C₆Cl₄H₂)

1 42.000 0.930 -0.073

2 186.000 0.770 -0.261

3 242.000 0.760 -0.274

4 360.000 0.640 -0.446

5 420,000 0.540 -0.616

EXAMPLE 18

The formation of gas (mostly trimethylamine) in the chemical dechlorination process competes with the reaction between the reagent and the targeted chlorinated hydrocarbons. In order to maximize the reaction of the reagent with the chlorinated hydrocarbons, and to minimize the formation of gas, a sequential addition procedure can be used to maintain relatively low concentrations of sodium tetrahydridoborate in the system. A reaction vessel was charged with chlorinated hydrocarbons (Aroclor^® 1248), a magnetic stir bar, sodium tetrahydridoborate (0.5 g), bis-(η⁵-cyclopentadienyl)titanium dichloride (80 mg), and N,N-dimethylformamide (30.0 mL). The bottle was isolated by an oil bubbler and was heated to 95°C. After 1.5 hours, additional sodium tetrahydridoborate (0.5 g) was added. Gas evolution was observed immediately. After an additional two hours, 0.5 g of sodium tetrahydridoborate was added. Two more additions of sodium tetrahydridoborate (0.5 g) were conducted within 1.5 hours, and the reaction mixture was further heated for 20 minutes. The total amount of sodium tetrahydridoborate added to the reaction mixture was 2.5 g, and the reaction was heated at 95°C for 5 hours and 20 minutes. The reaction mixture was quenched with 25 mL of water and extracted with ethyl acetate (25 mL). The ethyl acetate layer was collected, dried over sodium carbonate, filtered through a short column of silica gel and washed with ethyl acetate. GC analysis was conducted and the efficiency of dechlorination was higher than in the case of one-time addition of sodium tetrahydridoborate.

EXAMPLE 19

The reducing agent was prepared as in Example 12. (a) Reduction of PCB at 25½C

A 20 mL vial equipped with a magnetic stir bar was charged with Aroclor^® 1248 (12.8 mg) and the ex situ prepared reducing agent (10 mL, 10.0 mmol). Reductionproceeded slowly at 25ºC. (b) Reduction of Tetrachloroethylene

A flask equipped with a magnetic stir bar and 30 mL of the ex situ prepared reducing reagent (30 mmol) was charged with tetrachloroethylene (0.452 mg, 3.0 mmol), 1-chlorooctane (0.441 g), and nonane (0.44 g). The reaction mixture was held at 25°C for 40 hours, after which time analysis showed no tetrachloroethylene and only a small amount of chlorooctane remaining. (c) Reduction of 1 , 2, 3-Trichloropropane

A flask equipped with a magnetic stir bar and 1,2,3-trichloropfopane-contaminated sand (20 g sand; 0.5 g trichloropropane and 0.67 g decane as an internal analysis standard) and the ex situ prepared reducing reagent (30 mL; 30 mmol). The mixture was heated at 52°C for 3 hours; more than 95% 1,2,3-trichloropropane was reduced. (d) Reduction of 1,2, 3-Tetrachlorobenzene

A mixture of the ex situ prepared reducing reagent (40 mL; 64 mmol) and 1,2,4,5-tetrachlorobenzene (4.0 mmol) was held at 25°C for two weeks. More than 70% of the tetrachlorobenzene was reduced.

EXAMPLE 20

A flask equipped with a magnetic stir bar was charged with bis-(η⁵-cyclopentadienyl) titanium dichloride (55 mg,

0.22 mmol), sodium tetrahydridoborate (1230 mg, 32.5 mmol),

1,2,4,5-tetrachlorobenzene (0.449 g, 2.1 mmol), dimethylformamide (20.0 mL) and water (0.1 mL, corresponding to 1% water in the reaction mixture). The reaction was heated at 85ºC with the rate of reduction being shown in the following table.

0% Water

Time Mole Fraction

(Hours) C₄Cl₄

1 0.250 0.990

2 0.500 0.990

3 0.750 0.970

4 1.000 0.900

5 1.250 0.600

6 1.300 0.001

1% Water

Time Mole Fraction

(Hours) C₄Cl₄

1 4.000 0 .940

2 8.000 0.890

3 12.000 0.830

4 16.000 0.050 2% Water

Time Mole Fraction

(Hours) C₄Cl₄

1 12.500 0.900

2 14.000 0.860

3 16.000 0.820

4 18.000 0.780

5 20.000 0.020

5% Water

Time Mole Fraction

(Hours) C₄Cl₄

1 14.000 0 .920

2 18.000 0 .890

3 22.000 0 .860

4 26.000 0 .820

5 30.000 0 .770

6 34.000 0 .090 EXAMPLE 21

Titanocene dichloride (171 mg, 0.69 mmol), sodium tetrahydridoborate (622 mg, 16.4 mmol) and octachlorodibenzo-p-dioxin (195 mg, 0.39 mmol, 3.14 mmol C-Cl) were combined under a nitrogen atmosphere. bis-(2-Methoxyethyl) ether (20 ml) and pyridine (1.35 ml, 16.7 mmol) were injected under a nitrogen atmosphere. The reaction mixture then was heated at 125°C under a nitrogen atmosphere. The reaction was stopped after 3.5 hours by addition of water and the reaction mixture extracted by toluene. The toluene layer was purified by a short column of silica gel and analyzed by gas chromotography (GC). Octachlorodibenzo-p-dioxin was completely converted to dibenzo-p-dioxin, the only product detected by GC.

EXAMPLE 22

Titanocene dichloride (125 mg, 0.5 mmol), sodium tetrahydridoborate (454 mg, 12.0 mmol), and 4-bromobiphenyl (2.33 g, 10.0 mmol) were combined in a reaction vessel under a nitrogen atmosphere. bis-(2-Methoxyethyl) ether (20 ml) and pyridine (1.0 ml, 12.4 mmol) were injected under a nitrogen atmosphere. The reaction mixture was heated at 125ºC under a nitrogen atmosphere. An aliguot (about 1.0 1) was withdrawn by a syringe and quenched with water, and then the reaction mixture was ex..acted by diethyl ether. The ether layer was purified on a short column of silica gel and analyzed by gas chromotography/mass spectrometry (GC/MS). 4-Bromobiphenyl was completely reduced to biphenyl with a pseudo-first order rate constant, k = 0.94 h^-1.

EXAMPLE 23

Titanocene dichloride (125 mg, 0.50 mmol), sodium tetrahydridoborate (180 mg, 4.76 mmol), and decabromobiphenyl (300 mg, 0.318 mmol, 3.18 mmol C-Br) in a reaction vessel under a nitrogen atmosphere. bis-(2-Methoxyethyl) ether (10.0 ml) and pyridine (0.385 ml, 4.76 mmol) were injected under a nitrogen atmosphere and the reaction mixture then heated at 125°C under a nitrogen atmosphere. The reaction was stopped after 24 hours by addition of water, and the reaction mixture extracted by toluene. The toluene layer was purified on a short column of silica gel and analyzed by GC/MS. Quantitative analysis (by addition of tridecane as an internal standard) indicated biphenyl was the major reaction product.

EXAMPLE 24

Titanocene dichloride (75 mg, 0.30 mmol), sodium tetrahydridoborate (80 mg, 2.11 mmol), and 2,4,6-trichloro-p-terphenyl (15 mg, 0.045 mmol, 0.135 mmol C-Cl) were combined under a nitrogen atmosphere. bis- (2-Methoxyethyl) ether (5.0 ml) and pyridine (0.17 ml, 2.10 mmol) were injected under a nitrogen atmosphere. The reaction mixture was heated at 125°C under a nitrogen atmosphere and the reaction then stopped after 16 hours by addition of water. The reaction mixture was extracted by toluene and the toluene layer purified on a short column of silica gel. Upon analysis by GC/MS, the starting material, 2,4,6-trichloro-p-terphenyl, was found to be completely converted to p-terphenyl, the only product detected by GC/MS. EXAMPLE 25

Titanocene dichloride (75 mg, 0.30 mmol), sodium tetrahydridoborate (80 mg, 2.11 mmol), and 1,2,3,4,-tetrachloronaphthalene (50 mg, 0.19 mmol, 0.75 mmol C-Cl) were combined in a reaction vessel under a nitrogen atmosphere. bis-(2-Methoxyethyl) ether (5.0 ml) and pyridine (0.17 ml, 2.10 mmol) were injected under a nitrogen atmosphere. The reaction mixture was heated at 125°C under a nitrogen atmosphere and stopped after 18 hours by addition of water. The reac- tion mixture was extracted by toluene and the toluene layer purified on a short column of silica gel. Upon analysis by GC/MS, 1,2,3,4-tetrachloronaphthalene was found to be completely reduced to naphthalene, the only product detected by GC/MS. EXAMPLE 26

A reaction vessel was charged with titanocene dichloride (75 mg, 0.30 mmol), sodium tetrahydridoborate (80 mg, 2.11 mmol) and octachlorodibenzofuran (30 mg, 0.068 mmol, 0.54 mmol C-Cl) under a nitrogen atmosphere. bis-(2-Methoxyethyl) ether (5.0 ml) and pyridine (0.17 ml, 2.10 mmol) were injected under a nitrogen atmosphere. The reaction mixture was heated at 125°C under a nitrogen atmosphere. The reaction was stopped after 16 hours by addition of water and then the reaction mixture extracted by toluene. The toluene layer was purified by a short column of silica gel and analyzed by GC/MS, which demonstrated that octachlorodibenzofuran was completely reduced to dibenzofuran.

EXAMPLE 27

A flask was charged with sodium tetrahydridoborate (200 mg, 5.29 mmol) and pentachlorophenol (381 mg, 1.43 mmol) in a dry box under a nitrogen atmosphere. bis-(2-Methoxyethyl) ether (10.0 ml) was injected into the flask and the reaction mixture was allowed to stand at 25 C° for 20 min. A solution of titanocene dichloride (125 mg, 0.5 mmol), sodium tetrahydridoborate (254, 6.71 mmol) and pyridine (1.0 ml, 12.4 mmol) in bis-(2-methoxyethyl) ether (10 ml) then was added and the reaction mixture was heated at 125°C under a nitrogen atmosphere for 4 hours. The reaction mixture was acidified by dilute hydrochloric acid and extracted by diethyl ether. GC/MS analysis showed pentachlorophenol had been reduced to a mixture of mostly monochlorophenol and some chlorobenzene.

EXAMPLE 28

A flask was charged with titanocene dichloride (125 mg, 0.5 mmol), sodium tetrahydridoborate (454 mg, 12.0 mmol) and 1,4-dichlorobenzene (1.47 g, 10.0 mmol) in a dry box under a nitrogen atmosphere. To the above flask, bis-(2-methoxyethyl) ether (20.0 ml) and pyridine (1.0 ml, 12.4 mmol) were injected under a nitrogen atmosphere. An aliquot (about 1.0 ml) was withdrawn by a syringe and was quenched with water, and then was extracted by diethyl ether. The ether layer was purified by a short column of silica gel and was analyzed by GC and GC/MS. Dichlorobenzene was converted to chlorobenzene with a pseudo-first order rate constant, k = 0.20 h^-1.

Reduction reactions were run using 4-bromochlorobenzene (0.5M), sodium tetrahydridoborate (0.6 M), amine (0.6 M) and titanium catalyst (0.025 M) in bis-(2-methoxyethyl) ether at 125 °C. The effect of using various amines or mixtures of various amines on rates for 4-bromochlorobenzene reduction to chlorobenzene are (amine added, rate [k_obsh^-1]): pyridine, 1.01; 2-picoline, 0.67; 2, 6-lutidine, 0.03; 3,5-lutidine, 0.84; N,N-dimethyloctylamine, 0.06; N,N-dimethyloctylamine (0.3 M) plus pyridine (0.3 M), 1.4. These data show that sterically uncrowded pyridines are more effective promoters of the reduction reaction than are simple aliphatic amines, but that a mixture of an aliphatic amine and a pyridine is especially good. Reduction rates for other bromobenzenes under similar conditions (pyridine, 0.6 M) are: 4-bromobiphenyl, 1.11; p-dichlorobenzene, 0.20; 4-chlorobiphenyl, 0.22. EXAMPLE 29

Titanocene dichloride (175 mg, 0.70 mmol), sodium tetrahydridoborate (533 mg, 14.0 mmol) and 1,1,1-trichloro-2,2-bis-(4-chlorophenyl) ethane (500 mg, 1.41 mmol, 7.05 mmol C-Cl) were mixed under a nitrogen atmosphere and bis-(2-methoxyethyl) ether (10 ml), pyridine (0.57 ml, 7.05 mmol) and N,N-dimethyloctylamine (1.44 ml, 7.00 mmol) were injected under a nitrogen atmosphere. The reaction mixture was heated at 125ºC. An aliquot (about 1.0 ml) was withdrawn, quenched with water, and extracted with ethyl acetate. The ethyl acetate layer was purified though a short column of silica gel and analyzed by GC/MS. The starting material 1,1,1-trichloro-2,2-bis-(4-chlorophenyl)-ethane was completely reduced in 20 minutes, and 1,1-bis-(4-chlorophenyl) ethane (40%), 1-phenyl,1-(4-chlorophenyl) ethane (50%) and 1,1-biphenylethane (10%) were obtained. After further heating at 125°C for 1.67 hours (total 2 hours), 1,1-bis-(4-chlorophenyl)ethane (1%), 1-phenyl-1-(4-chlorophenyl) ethane (32%) and 1,1-biphenylethane (67%) were found to be present. Only 1,1-biphenylethane was present after further heating at 125°C for 2 hours (total 4 hours).

EXAMPLE 30

Titanocene dichloride (125 mg, 0.50 mmol) and sodium tetrahydridoborate (378 mg, 10.0 mmol) were mixed under a nitrogen atmosphere and bis-(2-methoxyethyl) ether (8.0 ml), pyridine (0.8 ml, 10.0 mmol), and tetrachloroethylene (0.2 ml, 8.00 mmol C-Cl) were injected under a nitrogen atmosphere. The reaction flask was sealed, and the reaction mixture was heated to 55°C with the vapor phase being sampled periodically. GC/MS analysis showed tetrachloroethylene was completely reduced to trichloroethylene and dichloroethylene (three isomers) in 20 hours.

EXAMPLE 31

High "organic content" garden soil (10.2 gm) was heated at 90°C to remove superficial water and was then spiked with

Aroclor^® 1248 (1.05 gm, 14.8 mmol C-Cl, 9.3% PCB by weight).

The soil sample was suspended in 20 ml of bis- (2- methoxyethyl) ether and heated at 125°C with titanocene dichloride (171 mg, 0.687 mmol, 0.05 equiv. per Cl), sodium tetrahydridoborate (822 mg, 21.7 mmol, 1.47 equiv. per Cl), pyridine (0.68 ml, 8.4 mmol, 0.57 equiv. per Cl) and N,N-dimethyloctylamine (1.73 ml, 8.4 mmol, 0.57 equiv. per Cl). A mixture containing about 50% biphenyl and about 50% 3-chlorobiphenyl was obtained after 24 hours of treatment.

By increasing the amount of reducing agent to a level sufficient to consume any residual moisture, the foregoing procedure can be used similarly on soil which has not been pre-dried. Hence while moisture reduces efficiency (by requiring more reducing agent), moisture is not a poison to the activity of the transition metal complex catalyst.

EXAMPLE 32

A freshly dried and spiked soil sample (10.2 gm soil, 1.02 gm Aroclor^® 1248, 14.4 mmol C-Cl, 9.1% PCB by weight) was heated at 125°C in 20 ml of bis-(2-methoxyethyl) ether in the presence of titanocene dichloride (366 mg, 1.47 mmol, 0.10 equiv. per Cl), sodium tetrahydridoborate (1.335 g, 35.28 mmol, 2.4 equiv. per Cl), pyridine (1.43 ml, 17.7 mmol, 1.2 equiv. per Cl) and N,N-dimethyloctylamine (3.63 ml, 17.7 mmol, 1.2 equiv. per Cl). After 12 minutes, a mixture consisting only of dichlorobiphenyls (about 70%) and monochlorobiphenyls (about 30%) was obtained. After further heating for a total of 2 hours, only biphenyl was observed.

EXAMPLE 33

A reaction vessel is charged with 171 mg (0.687 mmol) of titanocene dichloride and 622 mg (16.4 mmol) of sodium tetrahydridoborate under a nitrogen atmosphere. A solution of 1000 mg of Aroclor 1248, a polychlorinated biphenyl (3.43 mmol, based on an average MW 292, assuming 13.7 mmol of C-Cl functional groups), and 1.35 ml of pyridine (16.7 mmol) in 20 mL of bis-(2-methoxyethyl) ether is added. The reaction mixture is heated at 125°C. One milliliter aliquots are withdrawn periodically, quenched with water, extracted with ethyl acetate, purified by passing through a short column of silica gel, and analyzed by gas chromatography. Significant dechlorination is observed after 3.5 hours with total dechlorination to biphenyl after 8.4 hours.

TABLE 33

Chlorine Retention Percent

Peak Atoms Time (min) Start 3.5 Hrs 8.4 Hrs

1 0* 9.15 0.00 41.75 100.00

2 1 13.26 0.00 2.20 0.00

3 1 16.29 0.00 49.56 0.00

4 1 16.62 0.00 6.49 0.00

5 2 22.01 0.19 0.00 0.00

6 3 25.83 3.53 0.00 0.00

7 3 25.95 0.23 0.00 0.00

8 3 25.99 0.28 0.00 0.00

9 3 27.40 0.59 0.00 0.00

10 3 27.57 0.20 0.00 0.00

11 3 27.59 0.34 0.00 0.00

12 3 30.34 8.81 0.00 0.00

13 4 31.04 2.86 0.00 0.00

14 3 31.73 0.14 0.00 0.00

15 3 31.76 0.77 0.00 0.00

16 4 32.07 0.63 0.00 0.00

17 4 32.76 0.21 0.00 0.00

18 4 33.64 8.37 0.00 0.00

19 4 33.95 4.56 0.00 0.00

20 4 34.04 0.40 0.00 0.00

21 4 34.07 0.72 0.00 0.00

22 4 34.10 0.60 0.00 0.00

23 4 34.12 1.18 0.00 0.00

24 4 35.33 6.93 0.00 0.00

25 4 35.42 0.40 0.00 0.00

26 4 35.51 0.17 0.00 0.00

27 4 35.55 1.24 0.00 0.00

28 3 35.83 0.37 0.00 0.00

29 4 36.26 1.79 0.00 0.00

30 4 36.30 0.43 0.00 0.00

31 4 36.47 3.35 0.00 0.00

32 4 37.01 0.88 0.00 0.00

33 4 38.75 3.69 0.00 0.00

34 4 38.95 0.14 0.00 0.00

35 4 39.26 11.00 0.00 0.00

36 4 39.43 9.60 0.00 0.00

37 5 39.89 0.17 0.00 0.00

38 4 40.83 6.23 0.00 0.00

39 5 41.12 0.60 0.00 0.00

40 5 41.15 0.27 0.00 0.00

41 5 41.16 0.54 0.00 0.00

(cont'd next page) Chlorine Retention Percent

Peak Atoms Time (min) Start 3.5 Hrs 8.4 Hrs

42 5 41.65 2.56 0.00 0.00

43 5 42.00 0.77 0.00 0.00

44 5 42.02 0.67 0.00 0.00

45 5 43.37 1.24 0.00 0.00

46 5 43.98 1.51 0.00 0.00

47 5 44.26 0.72 0.00 0.00

48 5 44.79 3.88 0.00 0.00

49 4 44.99 0.30 0.00 0.00

50 5 45.65 0.55 0.00 0.00

51 5 47.35 3.01 0.00 0.00

52 6 49.37 0.17 0.00 0.00

53 6 49.40 0.17 0.00 0.00

54 5 49.53 0.80 0.00 0.00

55 5 49.56 0.78 0.00 0.00

56 5 49.59 0.44 0.00 0.00 * = biphenyl

EXAMPLE 34

One hundred forty milligrams of titanocene dichloride (0.56 mmol), 378 mg of sodium tetrahydridoborate (10.0 mmol) and 190 mg of 4-bromochlorobenzene (1.0 mmol) are introduced into a reaction vessel under a nitrogen atmosphere and 10 mL of bis-(2-methoxyethyl) ether are added. The reaction mixture is heated at 50°C and 1 mL aliquots are withdrawn periodically, quenched with water, extracted with diethyl ether, purified by passing through a short column of silica gel, and analyzed by gas chromatography.

TABLE 34 A

Time (mole fraction)

(hours) 4-Bromochlorobenzene Chlorobenzene

0.00 1.00 0.00

9.17 1.00 0.00

After 9.2 hours, 41.2 m of dimethylethylamine (0.56 mmol) are added and the reaction allowed to continue. TABLE 34B

Time (mole fraction) (hours) 4-Bromochlorobenzene Chlorobenzene

9.66 0.89 0.11

10.23 0.84 0.16

11.08 0.81 0.19

After 11.15 hours at 50°C, an additional 169 mg of dimethylethylamine (2.31 mmol) are added and the reaction allowed to continue.

TABLE 34C

Time (mole fraction)

(hours) 4-Bromochlorobenzene Chlorobenzene

13.40 0.70 0.30

13.75 0.47 0.53

14.28 0.23 0.77

14.97 0.09 0.91

15.85 0.00 1.00

EXAMPLE 35

One hundred twenty-five milligrams of titanocene dichloride (0.5 mmol), 454 mg of sodium tetrahydridoborate (12.0 mmol) and 1900 mg of 4-bromochlorobenzene (10.0 mmol) are introduced into a reaction vessel under a nitrogen atmosphere. Ten milliliters of bis-(2-methoxyethyl) ether and 1.65 mL of triethylamine (11.8 mmol) are added. The reaction mixture is heated at 73°C and 1 mL aliquots are withdrawn periodically, quenched with water, extracted with diethyl ether, purified by passing through a short column of silica gel, and analyzed by gas chromatography. Reduction of 4-bromochlorobenzene is observed with a rate of k_obs=2.36 × 10^-2 (h^-1). The reaction is quenched after 93.6% conversion.

EXAMPLE 36

One hundred twenty-five milligrams of titanocene dichloride (0.5 mmol), 378 mg of sodium tetrahydridoborate (10.0 mmol), 27 mg of sodium methoxide (0.5 mmol), and 190 mg of 4-bromochlorobenzene (1.0 mmol) are introduced into a reaction vessel under a nitrogen atmosphere and 10 L of bis-(2-methoxyethyl) ether are added. The reaction mixture is heated at 50°C and 1 L aliquots are withdrawn periodically, quenched with water, extracted with diethyl ether, purified by passing through a short column of silica gel, and anal zed b as chromato ra h .

After 3.75 hours, 416 mg of dimethylethylamine (5.69 mmol) are added and the reaction allowed to continue. The following results are obtained. TABLE 36B

Time (mole fraction)

(hours) 4-Bromochlorobenzene Chlorobenzene

4.117 0.578 0.422

4.617 0.383 0.617

5.183 0.207 0.793

6.300 0.068 0.932

11.167 0.000 1.000

Claims

WHAT IS CLAIMED IS:

1. In the process of reducing halide content in haiogenated aromatic hydrocarbons by reduction in the presence of a reagent comprising (i) at least one complex of a transition metal of group 4 or 5 with a multidentate or unidentate organic or inorganic ligand and (ii) a reducing agent, the improvement which comprises conducting the reduction in the presence of an aliphatic or aromatic amine and an inert organic solvent.

2. The process according to claim 1 wherein the haiogenated aromatic hydrocarbons are polychlorinated aromatic hydrocarbons.

3. The process according to claim 2 wherein the polychlorinated aromatic hydrocarbons are polychlorinated biphenyls.

4. The process according to claim 1 wherein the amine is trimethylamine, triethylamine, dimethylethylamine, N,N- dimethylaniline, N,N-dimethylnaphthylamine, pyridine, 1- methylimidazole, quinoline, or piperidine.

5. The process according to claim 4 wherein the amine is triethylamine, dimethylethylamine, or pyridine.

6. The process according to claim 1 wherein the inert organic solvent is diglyme, triglyme, bis-(2-ethoxyethyl) ether, tetrahydrofuran, dimethylsulfoxide, dimethylformamide, or ethylene glycol dimethyl ether.

7. The process according to claim 6 wherein the inert organic solvent is diglyme.

8. The process according to claim 1 wherein the reduction is conducted at temperatures of from about 50°C to about 150ºC.

9. The process according to claim 1 wherein the complex is bis-(η⁵-cyclopentadienyl) titanium dichloride.

10. The process according to claim 1 wherein the reducing agent is sodium tetrahydridoborate.

11. The process according to claim 1 wherein the haiogenated hydrocarbon is a polychlorinated aliphatic hydrocarbon.

12. The process according to claim 1 wherein the haiogenated hydrocarbon is a polychlorinated olefinic hydrocarbon.