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.