Transition metal benzyne complex
Transition metal benzyne complexes are organometallic complexes that contain benzyne ligands. Unlike benzyne itself, these complexes are less reactive although they undergo a number of insertion reactions.Examples
The studies of metal-benzyne complexes were initiated with the preparation of zirconocene complex by reaction diphenylzirconocene with trimethylphosphine.
The preparation of TaMe2 proceeds similarly, requiring the phenyl complex TaMe3. This complex is prepared by treatment of TaMe3Cl with phenyllithium. Upon heating, this complex eliminates methane, leaving the benzyne complex:
The second example of a benzyne complex is Ni. It is produced by dehalogenation of the bromophenyl complex NiCl with sodium amalgam. 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 Ni2.Structural trends
Several benzyne complexes have been examined by X-ray crystallography.
align="center"
| Bond | Ta | Ni | Zr |
| M-C1 | 2.059 | 1.868 | 2.267 |
| M-C2 | 2.091 | 1.870 | 2.228 |
| C1-C2 | 1.364 | 1.332 | 1.364 |
| C2-C3 | 1.410 | 1.389 | 1.389 |
| C3-C4 | 1.362 | 1.383 | 1.383 |
| C4-C5 | 1.403 | 0.93 | 1.380 |
| C5-C6 | 1.375 | 1.383 | 1.377 |
| C6-C1 | 1.408 | 1.386 | 1.406 |
| Angle | Ni | Zr |
| 1 | 41.9 | 35.3 |
| 2 | 69.2 | 70.8 |
| 3 | 69.1 | 73.9 |
| 4 | 122.9 | 120.2 |
| 5 | 122.3 | 122.1 |
| 6 | 116.1 | |
| 7 | 121.5 | |
| 8 | 121.0 | |
| 9 | 116.2 | |
