π-Stacking motifs in the crystal structures of bis(phosphine) copper(I) η2-tetrahydroborate complexes

The crystal and molecular structures of three bis(phosphine) copper(I) tetrahydroborate complexes have been determined at 125 K. Bis(tricyclohexylphosphine) copper(I) tetrahydroborate, (Cy3P)(2)Cu(BH4) (1), bis(tri-p-tolylphosphine) copper(l) tetrahydroborate, (p-tolyl(3)P)(2)Cu(BH4) (2) and bis(tri-p-methoxyphenylphosphine) copper(l) tetrahydroborate, (p-MeO-Ph3P)(2)Cu(BH4) (3) all exhibit a distorted tetrahedral 4-coordinate copper(I) ion. In each structure, the tetrahydroborate ligand is bound to copper through two hydrogen atoms in a bidentate fashion. In the structure of (Cy3P)(2)Cu(BH4) (1) the P-Cu-P bond angle of 132.45(2)degrees is significantly larger than the corresponding angle in the structures with aryl phosphine ligands, with a P-Cu-P bond angles of 119.91(2)degrees in (p-tolyl(3)P)(2)Cu(BH4) (2) and 121.51(5)degrees in (p-MeO-Ph3P)(2)Cu(BH4) (3). The arylphosphine analogs (p-tolyl(3)P)(2)Cu(BH4) (2) and (p-MeO-Ph3P)(2)Cu(BH4) (3) display intramolecular face-to-face pi-stacking interactions between an aryl group from each coordinated phosphine, at centroid-to-centroid distances of 3.768(1) and 3.581(3) angstrom, respectively, while (p-MeO-Ph3P)(2)Cu(BH4) (3) also exhibits intermolecular edge-to-face pi-stacking interactions. (C) 2012 Elsevier Ltd. All rights reserved.