245367-72-0Relevant academic research and scientific papers
Cobalt-Alkyne Complexes with Diphosphine Ligands as Mechanistic Probes for the Pauson-Khand Reaction
Derdau, Volker,Laschat, Sabine,Dix, Ina,Jones, Peter G.
, p. 3859 - 3864 (1999)
Enantiomerically pure (3,3-dimethylbutyne)[(R)-BINAP]Co2(CO)4 (6a) was obtained via thermal ligand exchange in 27% yield as a single diastereomer. X-ray crystal structure analysis of 6a revealed a basal bridged coordination of the BINAP ligand and a distorted geometry of the central Co2C2 core. Comparison of 6a with the structurally related (phenylacetylene)dppm)Co2(CO)4 (7) revealed that the geometric distortion is mainly caused by the BINAP ligand. Due to the replacement of basal CO ligands anti to the tert-butyl group in 6a by the diphosphine, the Pauson-Khand reaction of 6a with norbornene is completely suppressed. Comparison with (3,3-dimethylbutyne)(dppm)Co2(CO)4 (6b), (3,3-dimethylbutyne)(dppe)Co2(CO)4 (6c), 7, (3,3-dimethylbutyne)Co2(CO)6 (8a), and (3,3-dimethylbutyne)(PPh3)Co2(CO)5 (8b) showed a retardation of the reaction rate caused by phosphines. The mechanistic consequences for the Pauson-Khand reaction employing chiral phosphine ligands are discussed.
