SMALL HETEROBORANE CLUSTER SYSTEMS .8. PREPARATION OF PHOSPHABORANE CLUSTERS FROM THE REACTION OF POLYHEDRAL BORANES WITH LOW-COORDINATE PHOSPHORUS-COMPOUNDS - REACTION CHEMISTRY OF PHOSPHAALKYNES WITH DECABORANE(14)

The room-temperature reaction of equimolar quantities of phosphaalkyne RC=P (2a; R = (t)Bu; 2b, R = adamantyl) with the decaborane(12)-Lewis base adduct B10H12. 2CH(3)CN (3) resulted in the formation of new pho sphaborane compounds (phosphine-methylene ylides), nido-RC(H)PB10H13 ( 4a, R = (t)Bu; 4b, R = adamantyl), in good yield (approximately 50% ea ch). These slightly air-sensitive compounds were fully characterized b y H-1,B-11, C-13, and P-31 NMR, 2D B-11-B-11 COSY NMR, FT-IR, and mass spectroscopic analyses. The structures of 4a and 4b are proposed to c onsist of a nido-PB10 framework formally based upon a 26-skeletal-elec tron nido-[B11H11](-) parent compound. Only the phosphorus atom was ob served to be incorporated into the polyhedral framework with an exopol yhedral C(H)R group doubly bound to the cage phosphorus atom. Two rela ted mechanisms are proposed to account for the observed products from these reactions.