GB2259701A

GB2259701A - Complexes of metallated organic molecules comprising multiple or mixed metallic species

Info

Publication number: GB2259701A
Application number: GB9119871A
Authority: GB
Inventors: Ronald Snaith; Dominic Simon Wright; Matthew Gwilym Davidson; Paul Robert Raithby
Original assignee: Associated Octel Co Ltd
Current assignee: Innospec Ltd
Priority date: 1991-09-17
Filing date: 1991-09-17
Publication date: 1993-03-24
Anticipated expiration: 2011-09-17
Also published as: GB2259701B; GB9119871D0

Abstract

Multi- or mixed-metal coordination complexes of a first metal M and a second metal M<1>, are obtained by reacting a solid salt of the metal M<1>, e.g. fluoride, chloride, nitrate etc. under anhydrous conditions with a solution of an anhydrous coordination complex of the metal M in a hydrocarbon solvent, that coordination complex being of the Formula RxM.nL, where R is an organic group which is the residue of an organic compound RH, where H represents a labile hydrogen atom replaceable by the metal M, x is the valency of the metal cation M, L is an organic donor ligand (Lewis base) and n is a whole number representing the number of ligand molecules in the complex. In that reaction, cations of the metal M<1> are captured by and enter into the crystallographic structure of the complex RxM.nL to form a multi- or mixed-metal coordination complex of the formula RxM.nLM<1>aZb, where R x M n and L are as defined above, M<1> is the second metal cation (which may be the same as or different from the metal cation M), b is the valency of the metal cation M<1>, Z is the anion of said metal salt, e.g. fluorine, chlorine, nitrate etc., and a is the valency of that anion.

Description

COMPLEXES OP METALLATED ORGANIC MOLECULES COMPRISING MULTIPLE OR MIXED METALLIC SPECIES This invention relates to complexes of metallated organic molecules comprising multiple and preferably mixed metallic species.

As used herein the term "multiple metallic species" refers to complexes containing at least two metal atoms forming coordination centres in the molecular structure of the complex, those two or more atoms not necessarily being different metallic species. "Mixed metallic species" on the other hand does specifically imply two or more different metal atoms each forming a coordination centre within one and the same complex.

Metallated complexes, i.e. complexes of a metal salt and an aprotic donor ligand such as hexamethylphosphoramide (HMPA), tetramethylenediamine (TMEDA), pentamethyldiethylenetriamine (PMDETA) and other aprotic Lewis bases, are of potential interest in a variety of different applications e.g. as a hydrocarbon or oil-soluble source of a reactive metal M, or as volatile sources of a metal M for metaloxide chemical vapour deposition (MO-CVD) applications.

In our recently filed U.K. Patent Application GB 9106834.6, we have disclosed a method for the preparation of metallated complexes containing not only an aprotic Lewis base donor ligand, but also a small protic Lewis base ligand, such as HZ0, NH3, H2S, HZSe or CH30H, coordinating the metal cation.

These metallated complexes are prepared by reacting a solid compound of a metal M and the protic Lewis base ligand, that is to say an oxide or hydroxide of the metal M, or an amide, hydroselenide or methoxide, with an organic compound RH containing two eiectronegative centres in the organic group R and either immediately adjacent each other or separated by a small linking or bridging group or atom, one such centre providing an "active" hydrogen atom which is replaceable by the metal M, the reaction being carried out under substantially anhydrous conditions in an aromatic hydrocarbon solvent, preferably toluene, containing the aprotic Lewis base donor ligand L. The reaction takes place readily at room temperature, or with gentle heating of the reaction mixture upto the boiling point of the aromatic solvent.

The product complex, usually in a well defined crystalline form, is recovered upon cooling of the reaction solution, e.g. by refrigeration.

The reaction, in the case of the metal hydroxide reactants, may be represented by the equation:

(aquo-complex) Where M is the metal; x is the valency of the metal M; RH is an organic compound of the type Y-(R)-XH, where X and Y are both electronegative centres independently containing or consisting of N, O or S, and Rl is i) an aliphatic, aromatic or heterocyclic ring system, ii) a hydrocarbon or other aliphatic chain system, or (iii) a carbon atom attached to i) or ii) above or to hydrogen; L is the aprotic Lewis base donor ligand; n is the number of donor ligand molecules L, usually 1, 2, 3 or 4.

Similar equations and formulae may be written in the case of the amide, hydrosulphide, hydroselenide and methoxide reactants, save that in the formula of the product complex, the H20 ligand molecule is replaced by NH (ammino complexes) H2S (hydrosulphide complexes), H2Se (hydroselenide -complexes) or CHOH (methanol complexes), viz: RlM.nL.xNH3 (ammino) R,M. nL. xH,S (hydrosulphide) RxM.nL.xH2Se (hydroselenide) and RxM.nL.xCH30H (methanol).

The characteristic feature of those complexes, and the organic compounds RH used to prepare them, is that, in the organic compound RH, the hydrogen atom replaceable by the metal M is attached to a first electronegative centre X, e.g. O, S, or NH linked either directly or by a small bridging or linking group in the group Rl to a second electronegative centre Y provided by either a carbonyl oxygen atom, i.e. a > C = 0 group, a thione sulphur atom, i.e. a > C = S group, or an imide nitrogen atom, i.e. a = NH group. This group provides, in effect, a flexible electronegative side arm which, in the molecular structure of the compound RxM.nL, is attracted towards and forms a donor bond with the adjacent cation of the metal M.However, in the course of forming a complex with an inorganic protic Lewis base ligand molecule, i.e. a H20 ligand molecule in the case of the aquo complexes, a NH molecule in the case of the ammino complexes, an H2S or H2Se molecule in the case of the hydrosulphido and hydroseleno complexes respectively, or a CHOH molecule in the case of the methanol complexes, that bond is broken by the incoming protic Lewis base ligand molecule which then forms a hydrogen bond with the now displaced electronegative centre, i.e. the carbonyl oxygen atom, the thione sulphur atom or the imide nitrogen atom, as the case may be, and a new donor ligand bond with the metal cation.In effect, the "flexible" electronegative side arm "swings" away from metal cation to admit the incoming protic donor ligand, the molecular structure of the final complex thus showing a much increased interatomic spacing between the metal cation and the electronegative centre Y.

In the case of a typical aquo complex, and a typical heterocyclic organic acid 2-ercaptobenzoxazole, the structure of the complex may be represented as:

Where M represents the metal; L represents the aprotic Lewis base donor ligand; n is the number of ligand molecules L, usually 1 or 2; ------ represents a hydrogen bond; and

represents a donor ligand bond. A further characteristic of those aquo complexes is that, upon heating, they convert readily back into the anhydrous form, e.g.:

by loss of the H20 or other small protic donor ligand molecule - i.e.

NH3, H2S, H2Se or MeOH. That loss is accompanied by a reduction in the interatomic distance between the metal cation and the electronegative centre Y, i.e. in the case shown, the adjacent thione sulphur atom ( > C = S).

The preparation of anhydrous complexes of that type, e.g. the complex

has previously been described in J.Chem. Soc., Chem. Commun., 1990, Issue No. 8 p 643, com. 0/00262C.

In that case the anhydrous complex, which can be converted to the aquo complex by the addition of the stoichiometric quantity of water, is prepared by reacting a suitable source of the metal M, i.e. the metal itself, a metal hydride or metal alkyl, with the organic compound containing an "active" hydrogen atom replaceable by the metal M, such reaction being carried out in an aromatic hydrocarbon solvent, preferably toluene, and in the presence of the aprotic donor ligand or Lewis base L.

For example, the anhydrous lithiated complex referred to is prepared by the reaction of n-butyl lithium with 2-mercaptobenzoxazole in a solution of TMEDA in toluene, i.e. the reaction:

Because the conversion of that anhydrous complex into the corresponding aquo complex requires the closely controlled addition of the precise stoichimetric quantity of water (obtainable only under precise laboratory or experimental conditions) the direct route described in GB 9106834.6, i.e. the reaction of the organic compound containing the replaceable hydrogen atom with a solid metal oxide or hydroxide under anhydrous conditions in toluene, is much to be preferred.Similarly, that latter route has advantages in the preparation of the anhydrous complexes, in view of a) the readily available starting materials, i.e. oxides and hydroxides, and b) the ready dehydration of the aquo complexes by heating in vacuo.

The present invention is based on the discovery that those anhydrous complexes, i.e. coordination complexes of a) a compound formed from a metal M, preferably an alkali or alkaline earth metal such as Ca, Ba, or Sr, and an organic compound RH having an active hydrogen on a first electronegative centre and adjacent or near to a second electronegative centre in the organic group R, and replaceable by the metal M, and b) an aprotic donor ligand or Lewis base L coordinating the metal atom or atoms M, have the ability to form multiple or mixed metal complexes by the capture of a metal salt of the formula 1 where Mi is a metal cation, which may be the same as, but is preferably different from the metal M, Z is an anion, preferably halide, e.g. F, C1-, B & or I-, or NQ, , SO42, CO2, etc., a is the valency of the anion X and b is the valency of the cation ML.

In the course of the "capture" of the metal salt MlaZb by the complex RxM.nL (where R is the organic residue of the organic compound RH following the displacement of the "active" hydrogen by the metal M, L represents the aprotic donor ligand or Lewis base coordinating the metal M and n is the number of ligand molecules present in the complex and x is the valency of the metal M), it is found that the interatomic spacing between the metal atom M and the second electronegative centre in the group R increases to admit the incoming cation of the second metal Mt, which, in the multi-or mixed metal complex, forms a coordination centre for the electronegative centres in the R groups attached to the first metal M, with consequent displacement from the incoming salt of the anions Z.

Thus, generalising the formula hereinbefore given for the anhydrous complex to:

where M, L and n are as hereinbefore defined; Y is O, S or NH; X is O, S, NH or -CH; and R is an organic residue optionally forming a cyclic structure with X, the general formula of the product complex following the capture of the salt MlaZb may be represented by the formula:

where Mt represents the incoming metal cation, which may be the same as, but which will preferably be different from the first metal cation M, and which, in the product complex, becomes coordinated by the electronegative centres Y, whilst the incoming anions Z are displaced from the metal Ml onto the metal M.

The capture of the metal salt MlaZb by the anhydrous complex RxM.nL takes place readily upon dissolving the metal salt MlaZb in a solution of the anhydrous complex in an aromatic solvent, preferably toluene. Dissolving the metal salt in the anhydrous complex solution is assisted by heating and/or by agitation or stirring. The multi-or mixed metal coordination complex is recoverable, usually in a well defined crystalline form, by cooling the reaction mixture, e.g. by refrigeration, and following which the product complex can be purified, as necessary, by well established recrystallisation procedures.

The invention is illustrated by the following Example and accompanying drawings describing the preparation of a novel mixed metal coordination complex according to the present invention and illustrating the resulting molecular structures: Fig. 1 illustrating the molecular structure of the resulting complex cation, and Fig. 2 illustrating the molecular structure of the complex anion.

Example Synthesis and structure of the mixed metal-coordination complex (Ox2Ca.2HMPA)2.Pt Cl.(CaCl2.2HMPA). (toluene)2 Where "Ox" is the 2-mercaptobenzoxazolyl anion

Preparation of the anhydrous complex Ox2Ca.2HMPA The anhydrous complex Ox2Ca.2HMPA was prepared by the method of Example 2 of GB 9106834.6, that is to say by reacting substantially anhydrous solid calcium hydroxide with 2-mercaptobenzoxazole in solution in toluene in the presence of HMPA (HMPA = hexamethyl phosphoramide O:P(NMe2)3), following which the aquo complex, Ox2Ca.2HMPA.2H2O, was recovered in crystalline form, mp. 104-1060C.

Heating the aquo complex in vacuo at 130C for two hours provides

(aquo complex) (anhyd. complex) Reaction of anhydrous complex Ox2Ca.2HMPA with PtCl2 Platinum (II) chloride (0.266g, 1 mmol) was added to a solution of the anhydrous complex Ox2Ca.2HMPA (1.050g, 1.5 mmol) in 10 mL toluene. The mixture was heated to 1000C for 15 minutes by which time all the solid PtCl2 had reacted leaving a bright yellow solution and a small quantity of yellow powder, later determined to be Ox2Pt.

Filtration and cooling of the filtrate to 200C produced yellow cubic crystals of (Ox2Ca.2HMPA)2PtCl2.(CaCl2.2HMPA). 2 (toluene), first batch yield 0.66g 56%; m.p. 210-2130C; elemental analysis: found C 40.0, H 6.0, Cl 6.4, N 13.2, P 7.7%; calculated: C 40.4, H 6.0, Cl 6.1, N 13.3, P 8.0%; 1H NMR [(CD3)2SO, 250 MHz, 200C] 6 centred ca.7.1 (m,26H of four Ox anions and aromatic protons of two solvating toluene molecules), 2.53 (d,108H of six HMPA ligands, J 9.5Hz), 2.30 (s,6H, methyl protons of two solvating toluene molecules).

The solid state structure of the product complex, determined by X-ray crystallography, shows that it consists of a dinuclear calcium chloride-complexed cation, [(HMPA)3Ca. (ll2-Cl)3.Ca(HMPA)3]t, and a mixedmetal anion, [Pt(Ox)4.CaCl]; in addition, there are two toluene solvate molecules which lie in general positions in the lattice and do not interact strongly with either the cation or the anion. The cation (Figure 1) consists of two pseudo-octahedral Ca2t ions linked by three -C1 ions [mean Ca-Cl distance, 2.80(1)A] and complexed terminally by three HMPA ligands each [mean Ca-O distance, 2.27(2).

The structure of the anion is shown in Figure 2. Here a pt2 centre is coordinated by the four C. .. side-arms of four Ox groups [mean Pt-S distance, 2.32(2)A] to give a square planar coordination geometry (Pt deviates by 0.1 from the Sfl plane); such a square planar arrangement is the norm for Pt (II) complexes. The 2-N centres of these Ox anions in turn bind to a Ca2t centre [mean Ca-N distance, 2.46(2)] which lies directly above the Pt [Ca...Pt distance, 2.960(5)A]. Finally, a capping C renders the Ca2t centre square-based pyramidal. Overall, the anion structure can be viewed as a tetrapod OxsCaCl3 ligand coordinated to a Put2? cation.

By following the same general techniques, mixed-metal complexes have been prepared from the following reaction pairs: Metal Chelate Metal Salt Product (R,M.nL) (M'aZb) (RIM-nL-M aZb) Ox2Ca.2HMPA PdCl2 Orange crystals NiCl2 Yellow crystals CoCl2 Turquoise crystals " SnCl2 White powder PbBr2 Yellow powder OxzBa.3HMPA PdCl2 Orange crystals l(OxO)Ca.2HMPA TiCl3 Orange crystals 2(AntS)2Sr.3HMPA PtC12 Yellow crystals TlCl Brown solution OxOH = 2-hydroxybenzoxazole 2 AntSH = 5-anilino - 1, 2, 3, 4 - thiatriazole The overall reaction of the anhydrous complex Ox2Ca.2HPMA with the PtCl2 may thus be viewed as a "capture" of the PtC12 by the complex, with the ptZt cation displacing the side arm bonds between two Ca2t cations and the nearby sulphur atoms of their respective Ox anions in two molecules of the anhydrous complex, the incoming pt2t cation thus becoming a coordination centre for four coordinating sulphur atoms of four Ox anions, the ss-N centres of which remain bound to one Ca centre of the cation. As a result of that capture, also, the two anions of PtClZ are displaced, with one ending up in the dicalcium cation, and the other ending up in the mixed metal anion.

The above results are believed to be of considerable significance in showing the ability of anhydrous "side-arm" donating complexes of the type described, i.e. Lewis base donor ligand coordinated complexes of metal containing compounds of the type RM where M is a metal atom replacing an active hydrogen of an organic compound RH in which the hydrogen atom replaceable by the metal M lies close to an electronegative centre Y in the group R, to act as ligand to other metals, thus giving rise to mixed-metal complexes of the type described. Indeed it has already been shown that anhydrous complexes of the type described will dissolve salts of other metals besides platinum, e.g. PdCl2, CoCl2, NiCl2 and SnCl2 to give well defined crystalline products.

In the anhydrous complex, a wide variety of metal cations may be used: alkali metal cations, alkaline earth metal cations, rare earth and transition metal cations. It is also possible that the process of the invention will be applicable to the manufacture of mixed of alkaline earth metal complexes, i.e. containing two different alkaline earth metals, e.g. combinations of Ca/Ba, Ba/Sr, Ca/Sr, etc, and which may be of utility in mixed metal MO-CVD applications.

Likewise, the anhydrous complexes may be used to capture a wide range of metal salts, with particular interest centering on the capture of alkaline earth metal salts, as already indicated, to give rise to mixed alkaline earth metal complexes, on the noble metal salts, e.g.

Pt, Pd, etc., giving rise to mixed alkali metal/noble metal complexes and to mixed alkaline earth/noble metal complexes, and on the capture of transition metals to form mixed alkali or alkaline earth/transition metal complexes.

The organic compounds RH used to prepare the anhydrous complexes and containing an "active" hydrogen on a first electronegative centre X and close to a second electronegative centre Y in R and replaceable by the first metal M, may be any of a wide variety of organic compounds containing such an "active" hydrogen atom. Of especial interest are B-diketones, especially fluorinated diketones, i.e. compounds of the formula RFC(O)CH2C(O)Rg where R? is perfluoroalkyl, and heterocyclic compounds of the 2-mercaptobenzoxazole type, comprising a

group forming part of a heterocycle, Y being selected from 0, S and NH, especially 0 or S. Typical compounds of this type are listed in GB 9106834.6 and include, besides 2-mercaptobenzoxazole, succinimide, 2mercaptopyrimidine, 2-mercaptothiazoline, 2-mercaptobenzimidazole, 2 oxobenzazole and the nucleotide "bases" cytosine, thymine, uracil, guanine and adenine.

As the aprotic donor ligand or Lewis base, hereinbefore mentioned, i.e. HMPA, TMEDA, PMDETA, etc, numerous other. such donor ligands will be apparent to the person skilled in the art and will include - inter alia: N.N-dimethylpropylidene urea (DMPU), diethyl ether, 1,2-dimethyloxyethane (glyme), bis(2-methoxymethyl) ether (diglyme), dioxan, tetrahydrofuran and dimethylimidazole (DMI) etc.

Claims

1. A multi-or mixed metal coordination complex of a first metal M, and containing a second metal Mt, which may be the same as or different from the metal M, and obtainable by reacting a solid salt of the metal M under substantially anhydrous conditions with a solution of a substantially anhydrous coordination complex of the first metal M in an aromatic hydrocarbon solvent, the said substantially anhydrous coordination complex being of the formula R,M.nL, where R is the residue of an organic compound, containing an active hydrogen replaceable by the metal M and located on a first electronegative centre adjacent or near to a second electronegative atom in the organic group R, L is an aprotic donor ligand or Lewis base, n is a number indicating the number of ligand molecules in the complex and x is the valency of the metal M, the multi-or mixed metal coordination complex being representable by the formula RxM.nL.MlaZb, where M and Ml and the first and second metals, respectively, R, n, x, and L are as above defined, Z is an anion, a is the valency of the anion Z and b is the valency of the metal Ml.

2. A coordination complex according to claim, wherein M and M1 are different.

3. A coordination complex according to claim 1 or 2, wherein M is an alkali metal an alkaline earth metal, a noble metal or a transition metal.

4. A coordination complex according to claim 1, 2, or 3, wherein is an alkali metal, an alkaline earth metal, a noble metal or a transition metal in general.

5. The complex (OxZCa.2HMPA)2.PtCl.(CaClg.2HMPA) (toluene) where Ox = 2-mercaptobenzoxazolyl and HMPA represents hexamethylphosphoramide.

6. A method for the preparation of multi-or mixed metal coordination complexes of a first metal M, containing a second metal Ml, which may be the same as or different from the metal M, which comprises reacting, under substantially anhydrous conditions, a solution of a substantially anyhdrous coordination complex of the first metal M in an aromatic hydrocarbon solvent, the said substantially anhydrous coordination complex being of the formula Rt.M.nL, where R is the residue of an organic compound containing an active hydrogen replaceable by the metal M and located on a first electronegative centre adjacent or near to a second electronegative atom in the organic group R, L is an aprotic donor ligand or Lewis base, n is a number indicating the number of ligand molecules in the complex and x is the valency of the metal M, with a solid salt of the metal M and representable by the formula MlaZb where Z is an anion of valency a and b is the valency of the metal cation Mt thereby to produce a multi-or mixed-metal coordination complex of the formula RxM.nL.MlaZb where M, M1, R, L, Z, a, b, n and x are as above defined.

7. A method according to claim 6, wherein M is an alkali metal, an alkaline earth metal, a noble meta] or a transition metal.

8. A method according to claim 6 or 7 wherein Ml is an alkali metal, an alkaline earth metal, a noble metal or a transition metal.

9. A method according to claim 6, wherein M is an alkali metal, an alkaline earth metal, a noble metal or a transition metal, and M1 is an alkali metal, alkaline earth metal, a noble metal or a transition metal, M and M1 being different.

10. A method according to claim 9, wherein M is an alkali metal and M1 is an alkaline earth metal, or M is an alkali metal or alkaline earth metal and M1 is a noble metal or a transition metal.

11. A method according to any one of claims 6 - 8, where Z in the formula of the metal salt is F, C1, Br, I, NQ , soll or CQ2

12. A method according to any one of claims 6 to 12, where R in the formula of the anhydrous coordination complex is derived from a 13diketone or a heterocyclic organic compound containing a

group as part of the heterocyclic ring where Y is O, S or NH.

13. A method according to claim 12, where R is 2mercaptobenzoxazolyl, 2-mercaptopyrimidyl, 2-mercaptothiazolyl, 2mercaptobenzimidazolyl or 2-oxobenzazolyl.

14. A method according to any one of claims 6 to 11, where L in the formula of the anhydrous coordination complex is HMPA, TMEDA, PMDETA, DMPU, DMI, diethylether, 1,2-methyloxyethane, bis(2-methoxymethyl) ether, dioxan or tetrahydrofuran.

15. A method according to any one of claims 6 to 14, wherein the hydrocarbon solvent for the reaction is toluene.