Copper(I) borohydride complex with bis[(2-diphenylphosphino)phenyl] ether. Structure investigation by single-crystal X-Ray diffraction and DFT calculations

The borohydride anion is characterized by a rich coordination chemistry because of the variable denticity and the possibility of behaving as terminal or bridging ligand. The copper(I) complex Cu(k2-BH4)(DPEphos), where DPEphos is bis[(2-diphenylphosphino)phenyl] ether, was recently synthesized from CuCl using NaBH4 as borohydride source. The product crystallized from dichloromethane/ethanol (space group P1 ̅). The asymmetric unit contains two non-equivalent molecules, both exhibiting k2 coordination mode of the borohydride ligand, as suggested also by IR and 1H NMR spectra. The same Cu(I)-BH4 interaction was already observed for the related bis(triphenylphosphine) complex. The Cu-H distances are comprised between 1.67(3) and 1.75(2) Å, while the B-H distances are in the 1.07(2) – 1.20(2) Å range. The H-Cu-H angles for the two non-equivalent molecules are 62.7(12) and 66.3(10)°. DPEphos behaves as chelating ligand, with bite angles of 111.663(16) and 116.190(17)°. The Cu-P distances are between 2.2300(4) and 2.2776(5) Å. Bond lengths and angles of the first coordination sphere were compared with those obtained from DFT geometry optimizations, carried out using hybrid and range-separated functionals with variable percentage of Hartree-Fock exchange.