Monocarbollide complexes of osmium: X-ray crystal structure of [Os(CO) 3{η 5-5-(NMe 3)-7-CB 10H 10}

Abstract

In bromobenzene at reflux temperatures the compounds [Os 3(CO) 12] and [N(PPh 3) 2][ nido-7-CB 10H 13] yield a mixture of the anionic tri- and mono-osmium complexes [Os 3(CO) 8(η 5-7-CB 10H 11)] − and [Os(CO) 3(η 5-7-CB 10H 11)] −, respectively, characterized as their [N(PPh 3) 2] + salts ( 2b, 3c). Protonation of 2b with HBF 4·Et 2O in thf (tetrahydrofuran) yields the hydrido cluster complex [Os 3(μ-H)(CO) 8(η 5-7-CB 10H 11)] ( 4b), whilst treatment of 2b in the same solvent with CuCl and PPh 3 in the presence of TlPF 6 affords the bimetallic complex [Os 3(μ-H)(CO) 8{η 5-10-Cu(PPh 3)-7-CB 10H 10}] ( 5b). In contrast, the compounds [NHMe 3][ nido-7-CB 10H 13] and [Os 3(CO) 12] in refluxing bromobenzene give the novel zwitterionic complex [Os(CO) 3{η 5-5-(NMe 3)-7-CB 10H 10}] ( 6). The structure of 6 was determined by X-ray crystallography, revealing an Os(CO) 3 moiety η 5-ligated by the carborane cluster in which, unusually, the NMe 3 ligand is bonded to a boron atom on the upper B 5 belt.