Silver as an Exopolyhedral Auxiliary to the Rhenacarborane Anion [Re(CO)3(η5-7,8-C2B9H11)]-

The rhenacarborane salt Cs[Re(CO)3(η5-7,8-C2B9H11)] (1) has been used to synthesize the tetranuclear metal complex [{ReAg(μ-10-H-η5-7,8-C2B9H10)(CO)3}2{μ-Ph2P(CH2)2PPh2}] (3) where two [ReAg(μ-10-H-η5-7,8-C2B9H10)(CO)3] fragments have been shown by X-ray crystallography to be bridged by a single 1,2-bis(diphenylphosphino)ethane ligand. Reaction of 1 with Ag[BF4] in the presence of the ligands bis- or tris(pyrazol-1-yl)methane yields the complexes [ReAg(μ-10-H-η5-7,8-C2B9H10)(CO)3{κ2-CH2(C3H3N2-1)2}] (4) or [{ReAg(μ-10-H-η5-7,8-C2B9H10)(CO)3}2{μ-κ1,κ2-CH(C3H3N2-1)3}] (5), respectively. From X-ray studies, the former comprises a Re−Ag bond bridged by the carborane cage and with the bis(pyrazol-1-yl)methane coordinating the silver(I) center in an asymmetric κ2 mode. Complex 5 was unexpectedly found to contain a tris(pyrazol-1-yl)methane bridging two [ReAg(μ-10-H-η5-7,8-C2B9H10)(CO)3] fragments in a κ1,κ2 manner. Treatment of 1 with Ag[BF4] in the presence of 2,2‘-dipyridyl and 2,2‘:6‘,2‘ ‘−terpyridyl yields [ReAg(μ-10-H-η5-7,8-C2B9H10)(CO)3{κ2-(C5H4N-2)2}] (6) and [ReAg(μ-10-H-η5-7,8-C2B9H10)(CO)3{κ3-C5H3N(C5H4N-2)2-2,6}] (7). The X-ray structure determination of 7 revealed an unusual pentacoordinated silver(I) center, asymmetrically ligated by a κ3-2,2‘:6‘,2‘ ‘-terpyridyl molecule. The same synthetic procedure using N,N,N‘,N‘-tetramethylethylenediamine gave a tetranuclear metal complex [{ReAg(μ-10-H-η5-7,8-C2B9H10)(CO)3}2{μ-Me2N(CH2)2NMe2}2] (8) which is believed, in the solid state, to be bridged between the silver atoms by two of the diamine molecules. The salt 1 with Ag[BF4] in the absence of any added ligand gave the tetrameric cluster [ReAg{μ-5,6,10-(H)3-η5-7,8-C2B9H8}(CO)3]4 (9) where, in the solid state, four [ReAg(μ-10-H-η5-7,8-C2B9H10)(CO)3] units are held together by long interunit B−H ⇀ Ag bonds.