Silver as an exopolyhedral auxiliary to the rhenacarborane anion [Re(CO)3(eta5-7,8-C2B9H11)]-

The rhenacarborane salt CsRe(CO)3(eta5-7,8-C2B9H11)] (1) has been used to synthesize the tetranuclear metal complex ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2mu-Ph2P(CH2)2PPh2]] (3) where two ReAg(mu-10-H-eta5-7,8-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 AgBF4] in the presence of the ligands bis- or tris(pyrazol-1-yl)methane yields the complexes ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3kappa2-CH2(C3H3N2-1)2]] (4) or ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2mu-kappa1,kappa2-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 kappa(2) mode. Complex 5 was unexpectedly found to contain a tris(pyrazol-1-yl)methane bridging two ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] fragments in a kappa1,kappa2 manner. Treatment of 1 with AgBF4] in the presence of 2,2'-dipyridyl and 2,2':6',2' '-terpyridyl yields ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3kappa2-(C5H4N-2)(2)]] (6) and ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3kappa3-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 kappa3-2,2':6',2' '-terpyridyl molecule. The same synthetic procedure using N,N,N',N'-tetramethylethylenediamine gave a tetranuclear metal complex ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2mu-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 AgBF4] in the absence of any added ligand gave the tetrameric cluster ReAgmu-5,6,10-(H)3-eta5-7,8-C2B9H8](CO)3]4 (9) where, in the solid state, four ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] units are held together by long interunit B-H right harpoon-up Ag bonds.