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Transition metal benzyne complexes are
Transition metal benzyne complexes are organometallic complex
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
es that contain benzyne ligands (C6H4). Unlike benzyne itself, these complexes are less reactive although they undergo a number of insertion reaction
An insertion reaction is a chemical reaction where one chemical entity (a molecule or molecular fragment) interposes itself into an existing Chemical bond, bond of typically a second chemical entity ''e.g.'':
: + \longrightarrow
The term only ...
s.Buchwald, S. L.; Nielsen, R. B. "Group 4 Metal Complexes of Benzynes, Cycloalkynes, Acyclic Alkynes, and Alkenes" Chem. Rev. 1988, volume 88, 1047-1058
Examples
The studies of metal-benzyne complexes were initiated with the preparation of zirconocene complex by reaction diphenylzirconocene withtrimethylphosphine
Trimethylphosphine is an organophosphorus compound with the formula P(CH3)3, commonly abbreviated as PMe3. This colorless liquid has a strongly unpleasant odor, characteristic of alkylphosphines. The compound is a common ligand in coordination c ...
.Buchwald, S. L.; Watson, B. T. The Trimethylphosphine Adduct of the Zirconocene-Benzyne Complex: Synthesis, Reactions, and X-ray Crystal Structure. J. Am. Chem. Soc. 1986, 108, 7411-7413
:Cp2ZrPh2 + PMe3 → Cp2Zr(C6H4)(PMe3) + PhH
The preparation of Ta(η5-C5Me5)(C6H4)Me2 proceeds similarly, requiring the phenyl complex Ta(η5-C5Me5)(C6H5)Me3. This complex is prepared by treatment of Ta(η5-C5Me5)Me3Cl with phenyllithium
Phenyllithium is an organometallic agent with the empirical formula . It is most commonly used as a metalating agent in organic syntheses and a substitute for Grignard reagents for introducing phenyl groups in organic syntheses. Crystalline phenyl ...
.McLain, S. J.; Schrock, R. R.; Sharp, P. R.; Churchill, M. R.; Youngs, W. J. Synthesis of Monomeric Niobium- and Tantalum-Benzyne Complexes and Molecular Structure of Ta(η5-C5Me5)(C6H4)Me2" J. Am. Chem. Soc. 1979, volume 101, 263-265 Upon heating, this complex eliminates methane, leaving the benzyne complex:
:Ta(η5-C5Me5)(C6H5)Me3 → Ta(η5-C5Me5)(C6H4)Me2 + CH4
The second example of a benzyne complex is Ni(η2-C6H4)(dcpe) (dcpe = Cy2PCH2CH2PCy2). It is produced by dehalogenation of the bromophenyl complex NiCl(C6H4Br-2)(dcpe) with sodium amalgam
Sodium amalgam, with the common formula Na(Hg), is an alloy of mercury and sodium. The term amalgam is used for alloys, intermetallic compounds, and solutions (both solid solutions and liquid solutions) involving mercury as a major component. ...
. Its coordination geometry is close to trigonal planar.
Reactivity
Benzyne complexes react with a variety of electrophiles, resulting in insertion into one M-C bond. With trifluoroacetic acid, benzene is lost to give the trifluoroacetate Ni(O2CF3)2(dcpe).Structural trends
Several benzyne complexes have been examined byX-ray crystallography
X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...
.
References
{{Coordination complexes Organometallic chemistry Coordination chemistry Transition metals