Fluxional behaviour of phosphole and phosphine ligands on triosmium clusters

Abstract

The unsaturated cluster [Os 3 (µ-H) 2 (CO) 10 ] reacts with a variety of-conjugated phosphole ligands: 2,5-bis(2-thienyl)-1-phenylphosphole, 2,5-bis(2-pyridyl)-1-phenylphosphole, and 1,2,5triphenylphosphole, to give the monosubstituted [Os 3 (µ-H)(H)(CO) 10 (P)] and [Os 3 (µ-H) 2 (CO) 9 (P)] derivatives. Variable-temperature 1 H NMR studies for the decacarbonyltriosmium complexes show that the hydride ligands undergo fluxional behavior and its decarbonylation gave the nonacarbonyl unsaturated species with equivalent hydrides. An X-ray crystallographic analysis of [Os 3 (µ-H) 2 (CO) 9 (P)] (2b) (P = 1,2,5-triphenylphosphole) is reported. From 2,5-bis(2-pyridyl)-1phenylphosphole four isomers are obtained, the 1 H NMR spectrum at low temperature indicates that the phosphole ligand may occupy pseudoaxial and equatorial sites at one of the osmium atoms bearing the bridging hydride. The reaction of [Os 3 (CO) 10 (CH 3 CN) 2 ] with cyanoethyldiphenylphosphine affords mono-and bis(phosphine)-substituted clusters. The X-ray crystal structure of the monosubstituted [Os 3 (CO) 11 (η 1-PC 15 H 14 N)] (3) derivative is discussed. The dynamic behavior observed for [Os 3 (CO) 10 (η 1-PC 15 H 14 N) 2 ] (4) is studied by variable-temperature 1 H and 31 P{ 1 H} NMR spectroscopy. The latter studies show a mixture of two geometric isomers,

High variety of coordination modes of π-conjugated phospholes in dinuclear rhenium carbonyls. Fluxional behavior of σ,π-complexes

“…Due to the versatility of phospholes and metal carbonyl complexes, we have been exploring the interaction of both chemical entities. We have found σ-and σ,π-complexes, metal-metal bond cleavage and formation of derivatives where the phosphole ligand have undergone P-P and P-C bonds cleavage, C-H bond activation or partial hydrogenation of phosphorus ring [8,[38][39][40][41][42]. Herein, we have studied the reactivity of 2,5-disubstituted phenylphosphole derivatives with [Re 2 (CO) 8 (CH 3 CN) 2 ] to investigate coordination modes that could afford novel types of rhenium complexes.…”