199395-08-9Relevant academic research and scientific papers
Formation of cisoid-η4(5e)-Butadienylrhenium Complexes by Coupling of Alkene and Alkyne Ligands
Dossett, Stephen J.,Green, Michael,Mahon, Mary F.,McInnes, Jacqueline
, p. 767 - 768 (1995)
The reaction of the η2(4e)-bonded alkyne complexes 2-RC2Ph)(η-C5H5)> (R = Me or Ph) with o-diphenylphosphinostyrene and 2 equiv.AgBF4 in THF surprisingly affords HBF4, AgBr and excellent yields of the cationic η4(5e)-butadienyl complexes 3-(η-C5H5)>; the methyl-substituted system being structurally characterised by a single-crystal X-ray diffraction study.
Structure and reactivity of η4-cyclobutadiene and cisoid-η4(5e)-butadienyl-substituted rhenium complexes formed by reaction of [ReBr2{η2(4e)-alkyne}(η-C5H 5)] with alkynes or o-diphenylphosphinostyrene
Dossett, Stephen J.,Green, Michael,Mahon, Mary F.,McInnes, Jacqueline M.,Vaughan, Corinne
, p. 3671 - 3682 (2007/10/03)
When cis-/trans-[ReBr2(CO)2(η-C5H5)] and PhC2Ph were heated together under reflux in toluene solution for 24 h the η4-cyclobutadiene-substituted complex [ReBr2(η4-C4Ph4)(η-C 5H5)] 1 was formed in good yield via the intermediate [ReBr2{η2(4e)-PhC2Ph}(η-C 5H5)]. A single-crystal X-ray diffraction study confirmed an overall pseudo-tetrahedral structure for 1, establishing a Br-Re-Br angle of 83.9°. Treatment of 1 with PPh3 or PMe3 (L) in the presence of AgBF4 afforded the cations [ReBr(L)(η4-C4Ph4)(η-C 5H5)][BF4] 2 (L = PPh3) and 3 (L = PMe3). Reaction of 1 with an excess of Li[AlH4] gave the dihydride [ReH2(η4-C4Ph4)(η-C 5H5)] 4 characterised by X-ray crystallography, whereas, 1 equivalent of Li[AlH4] afforded [ReH(Br)(η4-C4Ph4)(η-C 5H5)] 5. In contrast with predictions from the Davis-Green-Mingos rules, reaction of 2 with Li[BHEt3] afforded 5 (major) and the minor product [ReH(PPh3)(η4-C4Ph 4)(η-C5H5)]Br 6. Extended Hueckel molecular orbital calculations suggested that protonation of 4 should give the cationic trihydride [ReH3(η4-C4Ph4)(η-C 5H5)]+, however a novel ring-opening reaction occurred with CF3CO2H to give the crystallographically characterised η4-1,3-diene complex [ReH{OC(O)CF3} {η2,η2-Z,Z-PhCH=C(Ph)C(Ph)=C(Ph)H} (H-C5H5)] 7. When [ReBr2{η2(4e)-PhC2R}(η-C 5H5)] (R = Me or Ph) was treated with AgBF4 (2 equivalents) and o-diphenylphosphinostyrene (dpps) a carbon-carbon coupling reaction between the co-ordinated alkyne and alkene part of the dpps ligand took place followed by a deprotonation reaction to give the cisoid-η4(5e)-butadienyl-substituted complexes [Re{=C(Ph)-η3-C(R)CHCH-C6H4PPh 2-o}(η-C5H5)][BF4] 8 (R = Me) and 9 (R = Ph); the structure of 8 being confirmed by single-crystal X-ray crystallography. Treatment of 9 with K[BHBu33] led to the selective delivery of 'H-' to the Re=Cα carbon of the η4(5e)-butadienyl ligand and formation of the crystallographically identified d6 η4-1,3-diene complex [Re{η4-CH(Ph)=C(Ph)CH=CHC6H4PPh 2-o}(η-C5H5)] 10. Interestingly, reaction of 10 with [Ph3C][BF4] led to regeneration of the parent cisoid-η4(5e)-butadienyl complex 9 confirming the relationship between η4(5e)-butadienyl and η4-1,3-diene ligands.
