Monocarbollide complexes of osmium: X-ray crystal structure of [Os(CO)(3){eta(5)-5-(NMe3)-7-CB10H10}]

In bromobenzene at reflux temperatures the compounds [OS3(CO)(12)] and [Ne( PPh3)(2)][nido -7-CB10H13] yield a mixture of the anionic tri- and mono-osm ium complexes [Os-3(CO)(8)(eta (5)-7-CB10H11)](-) and [Os(CO)(3)(eta (5)-7- CB10H11)(-), respectively, characterized as their [N(PPh3)(2)](+) salts (2b , 3c). Protonation of 2b with HBF4. Et2O in the (tetrahydrofuran) yields th e hydride cluster complex [Os-3(mu -H)(Co)(8)(eta (5)-7-CB(10)H11)] (4b), w hilst treatment of 2b in the same solvent with CuCl and PPh3 in the presenc e of TLPF6 affords the bimetallic complex [Os-3(mu -H)(CO)(8){eta (5)-10-Cu (PPh3)-7-CB10H10 }] (5b). In contrast, the compounds [NHMe3][nido-7-CB10H13 ] and [Os-3(CO)(12)] in refluxing bromobenzene give the novel zwitterionic complex [Os(CO)(3){eta (5)-5-(NMe3)-7-CB10H10}] (6). The structure of 6 was determined by X-ray crystallography, revealing an Os(CO), moiety eta (5)-l igated by the carborane cluster in which, unusually, the NMe3 ligand is bon ded to a boron atom on the upper B-5 belt. (C) 2000 Elsevier Science B.V. A ll rights reserved.