A homoleptic scandium trialkyl complex in combination with a borate compound served as an excellent catalyst for the C–H addition of aliphatic tertiary amines to various olefins.

We report the synthesis and isolation of three new σ-complexes of Cu(I) in which E–H (E = Al, Zn) σ-bonds are coordinated to copper. The addition of the main group hydride to a toluene-solvated Cu(I) complex results in reversible ligand exchange, and the Cu(I) σ-complexes have been crystallized. Experimental and computational data provide a wealth of evidence for weak binding of the E–H bond to Cu(I), which can be ascribed to σ-donation from the E–H bond into the 4s orbital of copper and back-donation from copper into the E–H σ* orbital.

A series of bis(σ-B-H) complexes of copper(i) have been prepared by displacement of arene solvent from a β-diketiminate copper(i) complex by four-coordinate boranes, H3B-L (L = NMe3, lutidine). In the presence of the same copper arene complex, the secondary amine-borane H3B-NMe2H undergoes dehydrogenation. We provide evidence for formation of a heterogengous catalyst from decomposition of the solution species.

The scope of the catalytic dehydrocoupling of primary and secondary amines with phenylsilanes has been investigated using [Y{N-(SiMe 3 ) 2 } 3 ] and a four-coordinate analogue bearing a cyclometalated phosphonium methylide ligand. Inclusion of the phosphorus-based ligand on yttrium results in increased substrate scope in comparison to the tris(amide) analogue. While reversible C−H bond activation of the cyclometalated ligand was observed in stoichiometric experiments, Dlabeling experiments and DFT calculations suggest that reversible ligand activation is not involved in silazane formation under catalytic conditions. We suggest that the extended reaction scope with the four-coordinate yttrium phosphonium methylide complex relative to the three-coordinate yttrium (tris)amide complex is a result of differences in the ease of amine inhibition of catalysis.