11-VERTEX AND 12-VERTEX POLYHEDRAL METALLADITHIABORANE CHEMISTRY - NOVEL COMPOUNDS FROM THE ARACHNO-[S2B9H10]- ANION - [(PPH(3))(3)H2IRS2B9H(10)], [(PPH(3))(2)HIRS2B9H(9)] AND [(PPH(3))(2)HRHS2B8H(8)]

Reaction of the arachno-[S2B9H10]- anon with [IrCl(PPh(3))3] yields (a ) [(PPh(3))(3)H2IrS2B9H10], in which cluster-metal interaction occurs solely via heteroatom eta(1) two-electron, two-centre, cluster-to-meta l donation, and (b) [(PPh(3))(2)HlrS(2)B(9)H(9)], which has a contiguo us nido-type twelve-vertex cluster structure with eta(5) cluster-to-me tal donation, whereas reaction with [RhCl(PPh(3))3] results in one-ato m cluster dismantlings to give nido-type eleven-vertex (c) [(PPh(3))(2 )HRhS2B8H8] and(d) [(PPh(3))(2)RhSB9H10], both with eta(4) cluster-to- metal donation.