Tris(bicyclo[1.1.1]pentyl)phosphine: An Exceptionally Small Tri- tert -alkylphosphine and Its Bis-Ligated Pd(0) Complex.

Tris(bicyclo[1.1.1]pentyl)phosphine can be prepared by radical addition of PH 3 to [1.1.1]propellane, giving the smallest tri- tert -alkylphosphine known. PBcp 3 is substantially smaller than PCy 3 and is comparable in electron-donating power to PEt 3 . It gives a bis-ligated Pd(0) complex Pd(PBcp 3 ) 2 that is exceptionally reactive toward alkyl halide oxidative addition and functions as a general ligand for palladium-catalyzed cross-coupling of sp 3 electrophiles. Radical addition of [1.1.1]propellane to phenylphosphine gives the bis(bicyclo[1.1.1]pentyl)phosphine derivative PBcp 2 Ph, illustrating the generality of this approach to bicyclopentylphosphine synthesis.