Unexpected White Phosphorus (P-4) Activation Modes with Silylene-Substituted o-Carboranes and Access to an Isolable 1,3-Diphospha-2,4-disilabutadiene

New types of metal-free white phosphorus (P-4) activation are reported. While the phosphine-silylene-substituted dicarborane 1, CB-SiP (CB=ortho-C,C '-C2B10H10, Si=PhC(tBuN)(2)Si, P=P[N(tBu)CH2](2)), activates white phosphorus in a 2 : 1 molar ratio to yield the P-5-chain containing species 2, the analogous bis(silylene)-substituted compound 3, CB-Si-2(,) reacts with P-4 in the molar ratio of 2 : 1 to furnish the first isolable 1,3-diphospha-2,4-disilabutadiene (Si=P-Si=P-containing) compound 4. For the latter reaction, two intermediates having a CB-Si2P4 and CB-Si2P2 core could be observed by multinuclear NMR spectroscopy. The compounds 2 and 4 were characterized including single-crystal X-ray diffraction analyses. Their electronic structures and mechanisms were investigated by density functional theory calculations.