199394-98-4Relevant academic research and scientific papers
Square Planar Coordination of Silver in a η4-Cyclobutadiene-(η5-C5H5)ReBr2 Complex Framework
Kleinschmidt, Steffen,Hinz, Alexander,Villinger, Alexander,Seidel, Wolfram W.
, p. 1268 - 1273 (2018)
Halide addition and abstraction experiments with the cationic rhenacyclopentatriene [(η5-C5H5){ReC4(SBn)4}Br]BF4 and the side-on cyclobutadiene complexes [(η5-C5H5)(η4-C4Ph4)ReX2] (X = Br, I), respectively, are described. Reversible interconversion of both coordination modes of the metal bonded C4R4 moiety depending on the presence or absence of the second bromide ligand is demonstrated for the sulfide derivative. However, formation of the [(η5-C5H5)(ReC4Ph4)X]+ congener by halide abstraction at [(η5-C5H5)(η4-C4Ph4)ReX2] turned out to be impossible. Instead, formation of silver halide complexes with the halide bridging rhenium and silver under retention of the metalorganic scaffold are observed. Governed by the phenyl substituent framework a square-planar coordination environment about the Ag cation is adopted for X = Br. Changing X = Br by X = I led to the formation of a heptanuclear complex with di- and three-coordinate silver ions.
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.
