Polyhedral metallathiaborane chemistry: Synthesis and characterisation of metallathiaboranes based on the twelve-vertex icosahedral closo-{MSB10H10} unit, where M is Rh or Ir

The reaction of [nido-7-SB10H12] with [RhCl(PPh3)3] in the presence of N,N,N′N′-tetramethylnaphthalene-1,8-diamine (tmnd) in CH2Cl2 gives twelve-vertex [2,2-(PPh3)2-2-H-closo-2,1-RhSB10H10] (1) and eleven-vertex [8,8-(PPh3)2-nido-8,7-RhSB9H10] (2), as major products, plus the dimeric species [{(PPh3)-closo-RhSB10H10}2] (3) as a minor product. Reaction of 1 with PMe2Ph in CH2Cl2 results in phosphine exchange and hydride substitution, affording the chloro analogue of 1, [2,2-(PMe2Ph)2-2-Cl-closo-2,1-RhSB10H10] (4). By contrast, reaction between [IrCl(PPh3)3] and [nido-7-SB10H12] in CH2Cl2 with tmnd affords only one product, twelve-vertex [2,2-(PPh3)2-2-H-closo-2,1-IrSB10H10] (5). [RhCl2(η5-C5Me5)]2 with [nido-7-SB10H12] under the same conditions gives twelve-vertex [2-(η5-C5Me5)-closo-2,1-RhSB10H10] (6). All the compounds are characterised by NMR spectroscopy, and by mass spectrometry, and the molecular structure of [2,2-(PMe2Ph)2-2-Cl-closo-2,1-RhSB10H10] (4) was established by single-crystal X-ray diffraction analysis. This last rhodathiaborane 4 is fluxional in solution through a process that involves a reversible partial rotation of the {RhCl(PMe2Ph)2} unit above the {SB4} pentagonal face of the {SB10H10} fragment.