855476-77-6Relevant academic research and scientific papers
Sigma-bond metathesis reactions of zirconocene alkyl cations with phenylsilane
Wu, Fan,Jordan, Richard F.
, p. 2688 - 2697 (2005)
The zirconocene methyl cations [(C5R5)ZrMe(ClC 6D5)] [B(C6F5)4] (C 5R5 = C5H5 (1a), C5H 4Me (1b)) react with PhSiH3 in the dark to yield [{(C 5R5)2Zr(μ-H)}2][B(C 6F5)4]2 (5a, b) and a mixture of PhxMeyHzSi products. The reaction proceeds by initial Zr-C/Si-H σ-bond metathesis via a four-center transition state in which Si is β to Zr. In the presence of light, significant amounts of [{(C5R5)2Zr(μ-Cl)}2] [B(C 6F5)4]2 (4a,b) are formed by photochemical reaction of (C5R5)2ZrH + species with the chlorobenzene solvent. The azazirconacycle [rac-(EBI)Zr{η2(C,N)-CH2CHMe(6-phenyl-2-pyridyl)}] [B(C6F5)4] (2, EBI = 1,2-ethylene-bis-indenyl) does not react with PhSiH3 at 23°C. However at 85°C, 2 deinserts propene to afford the η2-pyridyl complex [rac-(EBI)Zr{η2(C,N)-(6-phenyl-2-pyridyl)}][B(C6F 5)4] (6), which is catalytically isomerized to [rac-(EBI)Zr{η2(C,N)-2-(2-pyridyl)phenyl}][B(C6F 5)4] (7) by PhSiH3. The key step in this process is Zr-G/Si-H σ-bond metathesis of 6 with PhSiH3 via a transition state in which Si is α to Zr. The less crowded azazirconacycle [Cp2Zr{η2(C,N)-CH2CHMe-(6-methyl-2-pyridyl) }][B(C6F5)4] (3) reacts with PhSiH3 directly to afford [{Cp2Zr(SiPhH2)}2]-[B(C 6F5)4]2 (8) via a transition state in which Si is α to Zr. Steric factors may play a role in determining the selectivity of these reactions.
