Barium Siloxides and Catalysed Formation of Si-O-Si' Motifs.

The first unsupported barium siloxide, the homoleptic dimer [Ba2 {μ2 -OSi(SiMe3 )3 }3 {OSi(SiMe3 )3 }], is presented, and its structural features are discussed in the light of DFT computations. This complex, together with the related [Ba{μ2 -OSi(SiMe3 )3 }{N(SiMe3 )2 }]2 and their parent [Ba{N(SiMe3 )2 }2 ]2 , mediates the formation of asymmetric siloxanes R3 Si-O-SiR'3 through the first case of main group metal-mediated dehydrocoupling of silanols and hydrosilanes. Early kinetic analysis highlights an unusual catalytic manifold.