Facile two-electron reduction of a closo-rhodathiadecaborane

Abstract

Closo-to-arachno redox flexibility in metallaheteroboranes may be viewed as a metal-to-ligand cooperative action with application in catalysis. The treatment of [PSH][arachno-4-SB8H11] with [RhCl(PPh3)3] affords, after chromatography, three new 10-vertex rhodathiaboranes, [2,2,2-(H)(PPh3)2-closo-2,1-RhSB8H8] (3), [6,6,9-(PPh3)3-arachno-6,5-RhSB8H9] (4) and [2,2,2-(Cl)(H)(PPh3)-6-(PPh3)-closo-2,1-RhSB8H7] (5). 3 reacts quantitatively with PPh3 to form 4, which, in turn, reacts with chlorinated solvents to give the chloro-ligated cluster 5. Kinetic studies demonstrate that the reaction of 3 with PPh3 obeys a second-order rate law, with an associative mechanism. The Lewis acidity of 3 is quite remarkable, and, given its closo-to-arachno structural and electronic response, this cluster is expected to exhibit a rich chemistry.