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'-C 2 B 10 H 10 , Si=PhC(tBuN) 2 Si, P=P[N(tBu)CH 2 ] 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-Si 2 P 4 and CB-Si 2 P 2 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.