STERICALLY ENCUMBERED CHARGE-COMPENSATED CARBABORANES - SYNTHESIS ANDREACTIVITY - MOLECULAR-STRUCTURES OF 7-PH-11-SME2-7,8-NIDO-C2B9H10 AND 1-PH-3,3-(CO2-7-SME)(2)-3,1,2-CLOSO-RHC2B9H8

Reaction between K[7-Ph-7,8-nido-C2B9H11] and dmso in H2SO4 affords a mixture of the isomers 7-Ph-9-SMe2-7,8-nido-C2B9H10 (1a) and 7-Ph-11-S Me2-7,8-nido-C2B9H10 (1b). Similarly, starting from K[7,8-Ph-2-7,8-nid o-C2B9H10], the diphenyl analogue 7,8-Ph-2-9-SMe2-7,8-nido-C2B9H9 (2) was produced. These three new nido carbaboranes have been characterise d spectroscopically, including B-11-B-11 COSY and H-1-H-1 NOESY experi ments, and by a single crystal diffraction study on 1b. Deprotonation of 1a followed by addition of [RhCl(CO)(2)](2) affords the carbametall aborane 1-Ph-3,3-(CO)(2)-7-SMe2-3,1,2-closo-RhC2B9H9 (3), characterise d by R-1 and H-1 and B-11 NMR spectroscopies and by a crystallographic study. (C) 1997 Elsevier Science S.A.