Synthesis of Phosphine-Functionalized Silicon Cubane and Its Oxidative Addition, Giving a Bis(silyl)copper Complex.

A new strategy for the introduction of a second type of Si atom to silicon cubanes has been developed starting from the tricyclic hexasilane dianion [Ar 6 Si 6 ] 2- (Ar = 2,4,6-Me 3 C 6 H 2 ). Treatment of the dianion with Ar'SiCl 3 , followed by KC 8 , gave new types of octasilacubanes Ar 6 Ar' 2 Si 8 [Ar' = 2,4,6- i Pr 2 C 6 H 2 ( 3a ), 2-Ph 2 PC 6 H 4 ( 3b )] in high yields. Remarkably, treatment of cubane 3b bearing with two phosphine groups with 2 equiv of CuCl in CH 2 Cl 2 yielded the bis(silyl)copper complex via the selective oxidative addition of the newly formed Si-Si bond to Cu ion. Single-crystal X-ray analysis indicated the unique square-planar, four-coordinate Cu cation paired with the [CuCl 2 ] - counteranion.