Cyclic (Amino)(Phosphonium Bora‐Ylide)Silanone: A Remarkable Room‐Temperature‐Persistent Silanone

Abstract A silanone substituted by bulky amino and phosphonium bora‐ylide substituents has been isolated in crystalline form. Thanks to the exceptionally strong electron‐donating phosphonium bora‐ylide substituent, the lifetime at room temperature of the silanone is dramatically extended ( t 1/2 =4 days) compared to the related (amino)(phosphonium ylide)silanone VI ( t 1/2 =5 h), allowing easier manipulation and its use as precursor of new valuable silicon compounds. The interaction of silanone with a weak Lewis acid such as MgBr 2 increases further its stability (no degradation after 3 weeks at room temperature).