WO2010013239A2

WO2010013239A2 - SYNTHESIS OF STABLE C-(sup3)-CARBOMETALATED TRANSITION METAL COMPLEXES

Info

Publication number: WO2010013239A2
Application number: PCT/IL2009/000736
Authority: WO
Inventors: Dmitri Gelman; Clarite Azerraf
Original assignee: Yissum Research Development Co of Hebrew University of Jerusalem
Current assignee: Yissum Research Development Co of Hebrew University of Jerusalem
Priority date: 2008-07-31
Filing date: 2009-07-29
Publication date: 2010-02-04
Anticipated expiration: 2011-01-31
Also published as: WO2010013239A3

Abstract

The present invention provides a novel process for preparing carbometalated transition metal complexes, by reacting a transition metal complex having at least one conjugated diene ligand, with a dienophile, in a Diels-Alder cycloaddition reaction. In a particular embodiment, the invention discloses turning anthracene-based 9-C(sp²)-metalated complexes into C(sp³)-metalated ones by organic synthesis involving the Diels-Alder reaction.

Description

SYNTHESIS OF STABLE C- (sp³) -CARBOMETALATED TRANSITION

METAL COMPLEXES

Background: Transition metal catalysts are used for a variety of organic processes and have an immense importance in some industrial fields, such as in the reduction of ketones to alcohols, or of imines to amines and in the hydrogenation of olefins to alkanes. Furthermore, enantiomerically enriched products can be prepared by asymmetric transfer hydrogenation when the transition metal catalyst comprises an enantiomerically enriched ligand (also defined as "optically active" or "chiral non racemic" ligand) , ensuring that the double bond of a prochiral compound is asymmetrically reduced. In practice, this asymmetric transfer hydrogenation is often employed for the preparation of enantiomerically enriched alcohols from prochiral ketones.

The usefulness and importance of organometallic cyclometalated complexes of second- and third-row transition metals have necessitated synthetic methods for preparing them efficiently.

One synthetic route is reacting lithiated ligands with platinum or palladium compounds having good leaving groups (see for example, WO 00/57676) .

Organometallic cyclometalated complexes may also be formed by a direct reaction on the cyclometalating ligand, wherein the carbon-hydrogen is activated and replaced by the carbon-metal bond (see, for example US Patent No. 7,423,151).

Recently (PCT/IL2009/00356) , the present inventors have synthesized a novel family of transition metal complexes containing at least one pincer ligand comprising a cyclometalated sp³ hybridized carbon and two donor atoms. Pincer ligands are ligands which bind to the metal through at least three coplanar sites: two donor atoms and a metalated carbon which is linked to the metal in a σ (sigma) metal-carbon bond.

These complexes were characterized by a unique combination of high stability and high reactivity in catalytic transfer hydrogenation processes.

In PCT/IL2009/00356, complexes having general formula I were prepared by attaching a bulky, bidentate ligand through a third center on an sp³ cyclometalated carbon, thereby forming a tridentate pincer-type ligand having an sp³ cyclometalated carbon attached to the metal center.

wherein

M is selected from Ir or Rh;

Z is selected from:

Z¹ R¹ is independently selected from: Ci-Cε-alkyl, aryl, alkoxy, aryloxy, Ci-C₆-alkylamine, arylamine, halogen, N, 0 or hydrogen;

R³ and R⁴ are independently selected from: Ci-C_δ- alkyl, aryl, alkoxy, aryloxy, Ci-Cg-alkylamine and arylamine;

Wi and W₂ are independently selected from P, As, N and 0;

X¹ and X² are independently selected from: halogen, H, Ci-C₆-alkyl or null;

Y is selected from CO, RCN, N₂, alkene or null; and

R is selected from: Ci-C₆~alkyl, aryl, alkoxy, aryloxy, Ci-C₆-alkylamine and arylamine.

The method described in PCT/IL2009/00356 involved mixing a precursor complex of the formula MXL₂ and/or hydrates thereof (wherein X is a halogen and L is a monodentate ligand, or wherein L₂ is a bidentate ligand) with a ligand having the structure of Formula III in a solvent, thereby obtaining a reaction mixture. M, R¹, R², R³, R⁴, Z, W_α and W₂ are as defined for formula I hereinabove .

The reaction mixture was then heated to form the complex of formula I within the reaction mixture. Subsequently, the product was isolated from the reaction mixture .

9-C (sp²) -metalated complexes are readily available and structurally simple organometallic complexes (see for example: A) Haenel, M.W. et al., P. Chem. Ber. 1991, 124, 333. B) Haenel, M. W. et al . Angew. Chem., Int. Ed. 2001, 40, 3596. C) Yamashita, M. et al . , CHEM. -EUR. J. 2002, 8, 2976. D) Solin, N. et al . J. Am. Chem. Soc. 2004, 126, 7026)

It has now been found that it is possible to turn these anthracene-based 9-C (sp²) -metalated complexes into the more difficult to prepare C (sp³) -metalated ones by organic synthesis involving the Diels-Alder reaction. The Diels-Alder reaction, otherwise known as a cycloaddition reaction, involves reacting a conjugated diene with a double or triple bond, called a dienophile. The reaction is stereospecific, and is one of the few reactions that can be used to form two new bonds at the same time.

Detailed Description of the invention

The present invention provides a novel synthetic path for the preparation of a family of organometallic complexes recently described in PCT/IL2009/000356. This family of complexes presents a new class of electron-rich C (sp³) -cyclometalated complexes of transition metals (e.g. rhodium, iridium, platinum, palladium, nickel, ruthenium, etc.) based on the dibenzobarrelene and dibenzobarrelene- like scaffolds. The rigidity and chemical inertness of the polycyclic backbone in combination with the absence of easily abstractable β-hydrogens results in the formation of thermally and conformationally stable compounds, that are nonetheless extremely active catalysts for a variety of processes, such as polymerization, hydrogenation and more.

The inventors have now developed and demonstrated a general synthetic route toward preparing carbometalated transition metal complexes by a Diels-Alder cycloaddition reaction, having shown that a transition metal complex can act as a conjugated diene and react with a dienophile to successfully produce the cycloaddition reaction product.

Thus, according to one aspect of the invention, there is provided a process for preparing a carbometalated transition metal complex by reacting a transition metal complex having at least one conjugated diene ligand, with a dienophile, in a Diels-Alder cycloaddition reaction.

The term "carbometalated transition metal complex" refers to a transition metal complex containing a metal- carbon bond. The term "transition metal complex" will be understood by one skilled in the art as a compound which contains a transition metal linked to one or more ligands .

The process of the invention is suitable for the preparation of complexes of a variety of transition metals, in particular with any metal from Group VIII of the Periodic Table of Elements. Examples of such transition metals include silver (Ag) , palladium (Pd) , platinum (Pt) , ruthenium (Ru) , rhodium (Rh) , iridium (Ir) , copper (Cu) , nickel (Ni) , cobalt (Co) , osmium (Os) , and combinations thereof.

The term "ligand", otherwise known as "complexing agent" or "chelating agent", as used herein, refers to atoms or groups of atoms, which form coordination bonds to the central transition metal atom. The ligands can have different ligations, such as to be monodentate, bidentate, tridentate, tetradentate etc.

The term "conjugated diene ligand" refers to a ligand that includes at least two conjugated double bonds, each of which can be any type of double bond. Thus, for example, a component that includes a -CH=CH- CH=CH-CH=CH- structure constitutes a conjugated diene component even though it includes 3 or more double bonds. The conjugated diene ligand may be a cyclic conjugated diene ligand, in which case it refers to a conjugated diene ligand having at least one ring that includes at least one conjugated double bond located therein. The one or more other conjugated double bonds, for example, may also be located on the ring and/or may be located in a group attached to the ring.

According to a preferred embodiment, the transition metal complex having at least one conjugated diene ligand is an anthracene-based 9-C (sp²) -metalated complex. Such complexes are structurally simple to prepare, for example by heating a solution of the anthracene-based diphosphine ligand with an appropriate transition metal precursor, such as PdCl₂, PtCl₂, NiCl2 etc., with or without a base (e.g. EtsN) (for more details see: (a) M. W. Haenel et al., Chem. Ber., 1991, 124, 333; (b) M. W. Haenel et al . , Angew. Chem., Int. Ed., 2001, 40, 3596; (c) M. Yamashita et al., Chem. -Eur. J., 2002, 8, 2976; (d) N. Solin et al . , J. Am. Chem. Soc, 2004, 126, 7026) . As used herein, the term "dienophile" describes a compound which can interact with a conjugated diene in a Diels-Alder cycloaddition reaction. Dienophiles are typically unsaturated compounds, having a double bond or a triple bond. Examples of dienophiles include alkenes, alkynes, diazenes or carbazenes.

In a preferred embodiment, the dienophile is selected from:

5

H¹ H² H³ H⁴

10

Wherein Ra, Rb, Rc and Rd are independently selected from: Ci-Cε-alkyl, aryl, alkoxy, aryloxy, C₁-Cg- alkylamine, arylamine, halogen, N, 0 or hydrogen.

Diels-Alder reactions are facilitated by a combination of electron-withdrawing substituents on one of the reactants (diene or dienophile) and electron- releasing substituents on the other.

The reaction between the conjugated diene and the dienophile is also termed "4+2 Diels-Alder cycloaddition", referring to the^' electrocyclic reaction that involves the 4 π-electrons of the diene and the 2 IT- electrons of the dienophile.

As shown below, the inventors have demonstrated preparing C (sp³) -cyclometalated compounds via one-step transformation of their C(sp²) precursors, for example by effecting a 4+2 Diels-Alder cycloaddition of an anthracene-based 9-C (sp²) -metalated complexes as the conjugated diene with a suitable dienophile.

Thus, according to a preferred embodiment of the invention, there is provided a process for preparing a C (sp³) -carbometalated transition metal complex.

According to a particular embodiment, the carbometalated transition metal complexes which are to be prepared by this process are C (sp³) -carbometalated transition metal complexes containing at least one pincer ligand which is linked to the transition metal center through a carbon, termed Ca, and through two donor atoms W₁ and W₂. Pincer ligands combine bulkiness and steric hindrance with controllable electronic effects, and are also characterized in that the atoms Wi, W₂ and Ca are coplanar .

These complexes are further characterized in that the carbon atom linked to the metal (Ca) has to be part of a ring system (s), making Ca a cyclometalated carbon.

Furthermore, the Ca carbon has to be in an sp³ hybridization, and finally, the Ca carbon has to be bonded to three Cβ carbons and each of these Cβ carbons has to be linked only to non-hydrogen atoms. Namely, there should be no hydrogens linked to either Ca or to any carbon atom adjacent to Ca. Hence, no a-hydrogens or β-hydrogens, relative to the metal center, are present.

These complexes, which are described in detail in PCT/IL2009/000356 are in fact the first successful group of pincer complexes having an sp³-hybridized cyclometalated carbon, and having no α- or β-hydrogens.

As can be seen in the Examples section hereinbelow, the inventors have now successfully used some very rigid bicyclic C (sp²) -metalated precursors in combination with the stoichiometric or excessive amounts of organic molecules containing double or triple bonds, acting as dienophiles, in an organic solvent under thermal conditions to synthesize the desired complexes 6-8 in a Diels-Alder [4+2] reaction, as summarized in Scheme 1 below:

3: M=Pd 6: M=Pd 4: M=Ni 7: M=Ni 5: M=Pt M=Pt

Scheme 1

Complexes 6-8 were obtained in 64-80% yield and were found to have exceptional thermal stability and decomposition at 350 ⁰C, as determined through thermo gravimetric analysis. It should be stressed that in contrast, many known sp² pincer complexes have a decomposition temperature of about 250 ⁰C and previously known unstable sp³ pincer complexes have a decomposition temperature of up to about 170 ⁰C.

Thus, according to another aspect of the present invention, there is provided a process for preparing a compound of general formula A

wherein M is a transition metal selected from nickel (Ni) , palladium (Pd) , platinum (Pt) , ruthenium (Ru) , iridium (Ir) or rhodium (Rh) .

As demonstrated in formula A, the metal is directly bound to an sp³ hybridized cyclic carbon which is part of a pincer ligand. The direct metal-carbon bond renders this carbon an α-carbon relative to the metal center. It should be noted that neither this α-carbon, nor the carbons adjacent to it (β-carbons) have any hydrogens thereon. Thus, the pincer complex of formula A belongs to a special class of pincer complexes, which, as described in detail in PCT/IL2009/00356, are characterized by a useful combination of stability and reactivity in catalytic hydrogenation reactions . X¹ and X² are independently selected from: halogen, hydrogen, Ci-Cg-alkyl, or null; When either X¹ or X² is a halogen, it can be fluorine, chlorine, bromine, iodine or combination thereof, but is preferably one of the first three mentioned, more preferably chlorine. Y is selected from CO, RCN, N₂, alkene or null. It should be noted that converting any of these groups to another can be done according to known chemical procedures, and therefore complexes containing any of these Y groups are interchangeable with one another. R is selected from: Ci-Cβ-alkyl, aryl, alkoxy, aryloxy, Ci-C_δ-alkylamine and arylamine. Preferably the aryl is phenyl.

Wi and W₂ are donor atoms, independently selected from phosphorus (P) , arsenic (As) , nitrogen (N) or oxygen (O) . Preferably, at least one donor atom is a phosphorus (P) atom. More preferably, both donor atoms are phosphorus (P) atoms.

R³ and R⁴ are independently selected from: Ci-Cε- alkyl, aryl, alkoxy, aryloxy, Ci-C_δ-alkylamine and arylamine; Preferably, R³ and R⁴ are independently selected from Ci-Cβ-alkyl or aryl groups. More preferably, the aryl is phenyl.

It should be noted that since R³ and R⁴ cannot be hydrogen, there are no α-hydrogens (relative to the metal center) on the donor atoms W. Preferably, but not necessarily, R³ and R⁴ are chosen such that there will be also no β-hydrogens on the substituents .

R¹ and R² represent one or more substituent on the rings, whereas these substituents are independently selected from: Ci-Cβ-alkyl, aryl, alkoxy, aryloxy, Ci-Cβ- alkylamine, arylamine, halogen, N, O or hydrogen;

Z is selected from aryl, Ci-Cβ-alkyl or alkenyl groups. Preferably, Z is selected from one of groups Z¹- Z⁴, as depicted below:

Ra, Rb, Rc and Rd are independently selected from: Ci-C₆-alkyl, aryl, alkoxy, aryloxy, Ci-C₆-alkylamine, arylamine, halogen, N, 0 or hydrogen;

The process to obtain the complexes of general formula A comprises reacting a conjugated diene transition metal complex having general formula B

Formula B With a dienophile selected from H^x-H⁴ :

15

H¹ H² H³ H⁴

Wherein M, R¹, R², R³, R⁴, W₁, W₂, X¹, X², Y, Ra, Rb, Rc and Rd are as defined hereinabove.

The complexes of general formula B, having the conjugated diene ligands, are anthracene-based 9-C (sp²)- metalated complexes and are readily available and structurally simple to prepare or obtain, as described hereinabove.

The dienophiles H^x-H⁴ represent several groups of alkenes (H³ and H⁴) and alkynes (H¹ and H²) . It should be noted that the alkyne groups, in particular the strained triple bond of the benzyne (H¹) make very good dienophile. The reaction of complexes of general formula B with the dienophiles H¹-!!⁴ will result in cycloaddition products of general formula A containing Z^3--Z⁴ groups, respectively. According to a preferred embodiment of the present invention, the conjugated diene transition metal complex is a complex of formula Bl:

Formula Bl

Wherein M is a transition metal selected from nickel (Ni) , palladium (Pd) and platinum (Pt) , and the dienophile is dimethyl acetylenedicarboxylate (DMAD) , which is of the H² type:

MeO₂C == CO₂Me

Preferably, the process described herein is conducted such that the conjugated diene is first reacted with a solvent, to produce a suspension or a solution, prior to reacting it with the dienophile under heating.

Any solvent may be used for this stage; however, polar solvents are preferable, due to a better solubility of the starting materials and products.

As used herein, the term "polar solvent" refers to a solvent that has a permanent electrical dipole moment or a solvent that is capable of dissolving polar substances. Some examples of polar solvents can be found in Perry's Chemical Engineer's Handbook, Sixth Edition.

Some preferable solvents for the purpose of the present invention include, but are not limited to, methoxybenzene (anisole) , diethylene glycol dimethyl ether (diglyme) and dimethyl ether (DME) .

Preferably, the process described herein is conducted under reflux, generally at a temperature ranging from about 70 ⁰C to about 300 ⁰C. Typical reaction times may be from about 7 hours to about 50 hours. Preferably the reflux is conducted for about 24 hours . The method described herein may optionally further comprise separating the product from the reaction mixture and purifying the complex to obtain a purified form thereof.

The isolation and purification of the product can be conducted in any number of commonly used techniques, such as concentration of the reaction mixture by partially evaporating the solvent, precipitation of the complex by the addition of an anti-solvent, filtration of the solid

(or any other liquid/solid phase separation technique) and recrystallization.

Additional objects, advantages, and novel features of the present invention will become apparent to one ordinarily skilled in the art upon examination of the following examples, which are not intended to be limiting. Additionally, each of the various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below finds experimental support in the following examples . EXAMPLES

Reference is now made to the following examples, which together with the above descriptions, illustrate the invention in a non limiting fashion.

MATERIALS AND ANALYTICAL METHODS

1, 8-dibromoanthracene was synthesized according to 0. Grossman et al., Organometallics 2006, 25, 375.

NiCl₂(DME) and PtCl₂(CH₃CN)₂ were obtained from Strem. All other chemicals and metal precursors were purchased from Sigma-Aldrich and were used without further purifications .

¹H-NMR, ³¹P-NMR and ¹³C-NMR spectra were recorded on a Bruker 400 MHz instrument with chemical shifts reported in ppm relative to the residual deuterated solvent or the internal standard tetramethylsilane .

IR was measured using a Perkin Elmer 16PC FTIR. Gas chromatography analyses were performed on a Hewlett Packard 5890 instrument with a FID detector and a Hewlett Packard 25 m x 0.2 mm i.d. Supelcowax-10 capillary column .

Thermal stability of the complexes was determined using Thermogravimetric analysis (TSA) on a Perkin Elmer Pyris 1 TGA. X-ray crystallographic analysis was performed on a Bruker APEX CCD X-ray system.

Yields refer to isolated yields of compounds having purity greater than 95% as determined by proton Nuclear Magnetic Resonance spectroscopy (IH-NMR) analysis . Preparation of 1 , 8 -Bi s (d±phenylphosph±no) anthracene

(compound 1)

To a cold (-78⁰C) stirred solution of 1,8- dibromoanthracene (3 grains, 8.93 itαnol) in dry THF (35 rtiL) π-BuLi (1.6 M, 11.2 mL, 2 equiv) was added over a period of 30-35 minutes. The resulting yellow to brown solution was stirred for an additional 30 minutes, and a chlorodiphenylphosphine solution (3.2 mL, 17.86 mmol, 2 equiv) and THF (3 ml) were added dropwise. The brown-red solution was allowed to reach room temperature and was then refluxed for 1 hour. After the solution has cooled, ethyl acetate (50 mL) was added and the organic phase was successively washed with water dried and evaporated. The crude material was crystallized from methanol, affording 3.17 grams (64% yield) of a light-yellow powder (compound 1). ¹H NMR, 400 MHz (CDCl₃), δ: 7.04 (2H, t, J=6.1 Hz); 7.22-7.31 (2OH, m) ; 7.34 (2H, d, J=6.1 Hz); 7.98 (2H, d, J=8.6 Hz); 8.47 (IH, s) ; 9.81 (IH, t, J=5.3 Hz). ³¹P NMR, 400 MHz (CDCl₃), δ: -14.70.

Preparation of 1,8-Bis (diphenylphosphino) -9- anthrylpalladiwn(II) Chloride (Compound 3)

A suspension was prepared by mixing compound 1 (500 mg, 0.73 mmol and PdCl₂(CH₃CN)₂ (189.1 mg, 0.73 mmol) in ethylene glycol monomethyl ether (20 ml) . This suspension was heated at reflux to about 200 ⁰C for 2 hours. After cooling to room temperature, the green precipitate was filtered off, washed twice with methanol and dried in high vacuum to yield compound 3 (442 mg, 88% yield) . ¹H

NMR, 400 MHz (CDCl₃), δ: 7.40-7.50 (12H, m) ; 7.58 (2H, t,

J=7.3 Hz); 7.77 (2H,dd, J=5.1, J=Il.1 Hz); 7.96 (8H, m) ;

8.12 (2H, d, J=8.3 Hz); 8.33 (IH, s) . ³¹P NMR, 400 MHz (CDCl₃), δ: 42.92 ¹³C NMR, 400 (CDCl₃), δ: 122.6, 125.9 (t, J=4.8 Hz), 128.8 (t, J=5.2 Hz), 130.7, 131.3 (t, J=22.5 Hz), 131.6 (d, J=7.3 Hz), 133.8 (t, J=I .3 Hz) , 138.6, 146.5 (t, J=22.4 Hz). Anal. Calcd. For C₃₈H₂₇ClP₂Pd : C, 66.39; H, 3.96. Found: C, 66.25; H, 3.81.

Preparation of 1,8-Bls (diphenylphosphino) -9- anthrylnickel (II) Chloride (Compound 4)

A suspension was prepared by mixing compound 1 (500 mg, 0.73 mmol and NiCl₂(DME) (160.4 mg, 0.73 ramol) in ethylene glycol monomethyl ether (20 ml) . To this suspension diisopropylethylamine (0.12 ml, 0.73 mmol) was added and the mixture was heated at reflux to about 200 ⁰C for 2 hours. After cooling to room temperature the yellow precipitate was filtered off, washed twice with methanol and dried in high vacuum to yield Compound 4

(280 mg, 60% yield). ¹H NMR, 400 MHz (CDCl₃), δ: 7.40-7.45

(12H, m) ; 7.54 (2H, t, J=IO.1 Hz); 7.68 (2H, dd, J=5.0,

<J=9.1 Hz); 7.95 (8H, m) ; 8.07 (2H, d, J=9.1 Hz); 8.24 (IH, s) . ³¹P NMR, 400 MHz (CDCl₃) , δ: 41.87 ¹³C NMR, 400 (CDCl₃) , δ: 121.8, 126.1 (t, J=3.6 Hz) , 128.6 (t, J=5.10 Hz) , 129.1, 130.5, 131.1 (d, J=22.1 Hz) , 133.7 (t, J=6.4 Hz) , 139.0, 148.5. Anal. Calcd. For C₃₈H₂₇ClP₂Ni: C, 71.35; H, 4.25. Found: C, 71.29; H, 3.75.

Preparation of 1,8-Bis (diphenylphosphino) -9- anthrylplatinum(II) Chloride (Cowpovm.d 5)

A suspension was prepared by mixing compound 1 (500 mg, 0.73 mmol) and PtCl₂(CH₃CN)₂ (254 mg, 0.73 mmol) in ethylene glycol monomethyl ether (20 ml) . To this suspension diisopropylethylamine (0.12 ml, 0.73mmol) was added and the mixture was heated at reflux to about 200 0C for 2 hours. After cooling to room temperature the green precipitate was filtered off, washed twice with methanol and dried in high vacuum to yield Compound 5

(368 mg, 65% yield). ¹H NMR, 400 MHz (CDCl₃), δ: 7.45

(12H, m) ; 7.54 (2H, t, J=7.6 Hz); 7.8 (2H, dd, J=5.7, J=Il.8 Hz); 7.96 (8H, m) ; 8.12 (2H, d, J=8.0 Hz); 8.37

(IH, s) . ³¹P NMR, 400 MHz (CDCl₃) , δ: 39.65 (t, J=1495.3

Hz) . ¹³C NMR, 400 (CDCl₃) , δ: 120.64, 126.1 (t, J=4.9 Hz) ,

128.7 (t, J=5.5 Hz) , 130.8, 131.3 (d, J=27.4 Hz) , 133.0

(t, J=7.7 Hz) , 133.8 (t, J=6.9 Hz) , 138.6 (t, J=6.9 Hz) , 145.5 (t, J=18.1 Hz). Anal. Calcd. For C₃₈H₂₇ClP₂Pt: C, 58.81; H, 3.51. Found: C, 58.64; H, 3.58.

EXAMPLE 1 Preparation of complex 6 A suspension was prepared by mixing Compound 3 (200 mg, 0.29 mrαol) in diethylene glycol dimethyl ether

(diglyme, 5 ml). To this suspension (containing 0.058M of compound 3) was added dimethyl acetylenedicarboxylate

(DMAD) (0.053 ml, 0.47 mmol) and the obtained mixture was heated at reflux to about 100 ⁰C for 24 hours. After cooling to room temperature the solvent was reduced by evaporation under reduced pressure. An addition of methanol (5 cc) to the mixture results in a dark green precipitate. The solid was filtered off, washed twice with methanol and dried in high vacuum to yield Complex 6 (154 mg, 64% yield) .

Complex 6 showed exceptional thermal stability and decomposition at 350 ⁰C.

¹H NMR, 400 MHz (CDCl₃), δ: 3.20 (3H, s) ; 3.61 (3H, s) ; 5.79 (IH, s) ; 7.23 (4H, m) ; 7.30 (4H, t, J=I .1 Hz) ; 7.39 (2H, t, J=7.8 Hz) ; 7.47 (6H, m) ; 7.55-7.61 (6H, m) ; 7.82 (4H, m) . ³¹P NMR, 400 MHz (CDCl₃) , δ: 41.88 ¹³C NMR, 400 (CDCl₃) , δ: 50.5, 51.9 (d, J=45.85 Hz) , 126.41,127.1, 128.33 (t, J=5.5 Hz), 128.6, 128.7 (t, J=5.1 Hz), 130.3, 130.5, 130.7, 130.9, 133.6 (q, J=8.1 Hz), 140.8, 145.4 (t, J=IO.3Hz) ,162.4 (d, J=20.2 Hz), 164.1, 167.5. Anal. Calcd. for C₄₅H₃₆ClO₄P₂Pd : C, 63.99; H, 4.30. Found: C, 63.72; H, 3.32.

The structure of complex 6 was confirmed by x-ray crystallography.

EXZMBLE 2 P"reparation of Complex 7

A suspension was prepared by mixing Compound 4 (200 mg, 0.31 mmol) in diethylene glycol dimethyl ether

(diglyme, 5 ml) . To this suspension containing 0.062M of compound 4) was added dimethyl acetylenedicarboxylate (DMAD) (0.053 ml, 0.47 mmol) and the obtained mixture was heated at reflux to about 100 ⁰C for 24 hours. After cooling to room temperature the solvent was reduced by evaporation under reduced pressure. An addition of methanol (5 cc) to the mixture results in a dark red precipitate. The solid was filtered off, washed twice with methanol and dried in high vacuum to yield Complex 7

(177 mg, 73% yield) .

Complex 7 showed exceptional thermal stability and decomposition at 350 ⁰C.

¹H NMR, 400 MHz (CDC13) , δ: 3.65 (3H, s) ; 3.71 (3H, s) ; 5.58 (IH, s) ; 7.16 (2H, t, J=I .3 Hz) ; 7.23 (6H, t, J=7.5 Hz) ; 7.41-7.46 (1OH, m) ; 7.64 (4H, dd, .7=5.8, J=12.6Hz) ; 7.74 (4H, dd, J=6.3, J=ILlHz) . ³¹P NMR, 400 MHz (CDC13) , δ: 32.65 ¹³C NMR, 400 (CDC13) , δ: 51.9, 52.2 (d, J=9.5 Hz) , 125.88, 126.87 (t, J=2.6 Hz) , 127.99, 128.3 (t, J=4.8 Hz) , 128.6 (t, J=4.8 Hz) , 130.1 (d, J=41.4 Hz) , 131.6 (t, J=20.1 Hz) , 132.3 (m) , 133.4, 144.1 (t, J=8.1 Hz), 146.4, 163.6 (t, J=23.1 Hz), 166.7 (d, J=76.7 Hz). Anal. Calcd. for C₄₅H₃SClNiO₄P₂: C, 67.83; H, 4.55 . Found: C, 67.68; H, 3.16.

The structure of complex 7 was confirmed by x-ray crystallography.

EXAMPLE 3 Preparation of Complex 8

A suspension was prepared by mixing Compound 5 (200 mg, 0.26 mmol) in diethylene glycol dimethyl ether (diglyme, 5 ml) . To this suspension containing 0.052M of compound 5) was added dimethyl acetylenedicarboxylate (DMAD) (0.047 ml, 0.39 mmol) and the obtained mixture was heated at reflux to about 100 ⁰C for 24 hours. After cooling to room temperature the solvent was reduced by evaporation under reduced pressure. An addition of methanol (5 cc) to the mixture results in a light grey precipitate. The solid was filtered off, washed twice with methanol and dried in high vacuum to yield Complex 8 (167 mg, 80% yield) .

Complex 8 showed exceptional thermal stability and decomposition at 350 ⁰C.

¹H NMR, 400 MHz (CDCl₃), δ: 3.07 (3H, s) ; 3.58 (3H, s); 5.82 (IH, s) ; 7.18-7.33 (8H, m) ; 7.38 (2H, t, J=6.5 Hz); 7.48-7.53 (8H, m) ; 7.59 (4H, dd, J=6.8, J=13.3Hz); 7.85 (4H, dd, J=6.8, J=13.3Hz) . ³¹P NMR, 400 MHz (CDCl₃) , 5:42.37 (t, J=1578.2 Hz) . ¹³C NMR, 400 (CDCl₃), δ: 50.3, 51.4 (d, J=69.7 Hz) , 126.4, 126.9 (t, J=3.7 Hz), 128.2 (t, J=5.1 Hz) , 128.7 (t, J=5.5 Hz), 130.5 (d, J=28.7 Hz) , 133.5 (t, J=6.6 Hz) , 133.8 (t, J=I .1 Hz), 140.7, 145.5 (t, J=8.1 Hz) , 163.3, 164.0, 167.8. Anal. Calcd. for C₄₅H₃₆ClO₄P₂Pt: C, 57.91; H, 3.89. Found: C, 57.86; H, 3.81. The structure of complex 8 was confirmed by x-ray crystallography .

Claims

1. A process for preparing a carbometalated transition metal complex by reacting a transition metal complex having at least one conjugated diene ligand, with a dienophile, in a Diels-Alder cycloaddition reaction.

2. The process of claim 1, for preparing a C(sp³)- carbometalated transition metal complex.

3. The process of claim 2, wherein said transition metal complex having at least one conjugated diene ligand is an anthracene-based 9-C (sp²) -metalated complex.

4. The process of claim 2, wherein said dienophile is selected from:

H¹ H² H³ H⁴

Wherein Ra and Rb are independently selected from: Ci-Cβ- alkyl, aryl, alkoxy, aryloxy, Ci-C₆-alkylamine, arylamine, halogen, N, 0 or hydrogen.

5. A process according to claim 3, for preparing a C(sp³)- carbometalated transition metal complex of general formula A

Formula A

wherein

M is selected from Ni, Pd, Pt, Ru, Ir or Rh;

Z is selected from:

R¹, R², Ra, Rb, Rc and Rd are independently selected from:

Ci-C₆-alkyl, aryl, alkoxy, aryloxy, Ci-C₆-alkylamine, arylamine, halogen, N, 0 or hydrogen;

R³ and R⁴ are independently selected from: Ci-C₆-alkyl, aryl, alkoxy, aryloxy, Ci-C₆-alkylamine and arylamine;

Wi and W₂ are independently selected from P, As, N and 0;

X¹ and X² are independently selected from: halogen, H, Ci-

C₆-alkyl or null; and

Y is selected from CO, RCN, N₂, alkene or null; , said process comprising: reacting a conjugated diene transition metal complex having general formula B

Formula B

wherein M, R¹, R², R³, R⁴, W₁, W₂, X¹, X² and Y are as defined hereinabove,

With a dienophile selected from:

H¹ H² H³ H^<

Wherein Ra, Rb, Rc and Rd are as defined hereinabove.

6. The process of claim 5 wherein said conjugated diene transition metal complex is reacted with the dienophile in a solvent under heating.

7. The process of claim 6 wherein said solvent is a polar solvent .

8. The process of claim 6, being conducted under reflux.

9. The process of claim 8, wherein said reflux is conducted at a temperature ranging from about 70 °c to about 300 °c.

10. A process according to claim 5, for preparing the transition metal complex of general formula Al

Formula Al

wherein M is selected from Ni, Pd and Pt, , said process comprising: reacting a conjugated diene transition metal complex having general formula Bl

Formula Bl

wherein M is as defined hereinabove, with dimethyl acetylenedicarboxylate [DMAD) as the dienophile.

11. The process of claim 10, wherein M is Ni.

12. The process of claim 10, wherein M is Pt.

13. The process of claim 10, wherein M is Pd.