Synthesis and characterization of new 10- and 12-vertex CO-ligated metallathiaboranes

The reaction between [arachno-6-SB9H12]− and [IrCl(CO)(PMe3)2] affords the previously reported 11-vertex cluster, [8,8,8-(CO)(PMe3)2-arachno-8,7-IrSB9H10] (4), and small amounts of the new 10-vertex iridathiaborane [9,9,9,9-(CO)(H)(PMe3)2-arachno-9,6-IrSB8H10] (5). Alternatively, a rational synthesis of iridathiadecaboranes is effected from the reaction of the 9-vertex anion [arachno-4-SB8H11]− with [MCl(CO)(PPh3)2], to afford new CO-ligated 10-vertex metallathiaboranes of formulation, [9,9,9,9-(CO)(H)(PPh3)2-arachno-9,6-MSB8H10], where M = Rh (6) and Ir (7), in useful yields of 61% and 60% respectively. Treatment of the 11-vertex rhodathiaborane, [8,8-(PPh3)2-8,7-nido-RhSB9H10] (1) with nBuLi, followed by addition of [IrCl(CO)(PMe3)2] affords the 12-vertex iridarhodathiaborane, [1,2-(μ-CO)-1,1,2-(PMe3)3-2-(PPh3)-closo-1,2-IrRhSB9H9] (8) in low yield (0.7%). The 10-vertex metallathiaboranes, 5, 6 and 7, and the bimetallic 12-vertex cluster, 8, have been characterized by multinuclear NMR spectroscopy. In addition, the molecular structures of compounds 5, 6, and 8 have been studied by X-ray diffraction.