σ-BH activation of NHC→BH3 fragments at dinuclear Cu complexes

Abstract

We explored herein the coordination properties of bis(phosphine)NHC→BH3 ligand toward cationic and neutral Cu centres. The synthesis of three dinuclear Cu complexes featuring σ-BH interactions is reported. Noticeably, in each Cu complex, a BH moiety is bridging two Cu centres via two σ-BH interactions in a µ2-η1η1 BH coordination mode. NMR, IR, deuterium incorporation and X-Ray diffraction analyses, supported by DFT investigation enabled to finely measure the level of activation of the B-H bond depending on the coordination environment. The study shows gradual increase of activation whether the BH fragment is involved in none, one or two σ-BH interaction with Cu centres.