Amido Ca(II) complexes supported by Schiff base ligands for catalytic cross-dehydrogenative coupling of amines with silanes

A series of amido Ca complexes LCa[N(SiMe3)(2)](THF) (1-4) coordinated by Schiff base ligands L1-4 were synthesized via an amine elimination reaction between proligands L1-4H and a bisamido complex Ca[N(SiMe3)(2)](2)(THF)(2) in good yield. Unlike Ca[N(SiMe3)(2)](2)(THF)(2), the reactions of M[N(SiMe3)(2)](2)(THF)(2) (M = Yb, Sm) with proligands L1-4H do not lead to the formation of the target Ln(II) amido complexes. The reaction of Yb[N(SiMe3)(2)](2)(THF)(2) with (LH)-H-1 is accompanied by intramolecular C-H bond activation of a quinoline ring and results in the formation of complex 6 coordinated by a new trianionic [NNNNOO] ligand. The reactions of amido complexes 1 and 4 with PhSiH3 do not allow for preparing the related hydrides but afford homoleptic bis(phenolate) complexes 5 and 7 due to a ligand redistribution reaction. Amido complexes 1-4 were evaluated as precatalysts for cross-dehydrogenative coupling of silanes (PhSiH3, Ph(Me)SiH2, and Ph3SiH) and aliphatic, aromatic and cyclic amines (RNH2 and R2NH).