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)2Cu(BH4) (1), bis(tri-p-tolylphosphine) copper(I) tetrahydroborate, (p-tolyl3P)2Cu(BH4) (2) and bis(tri-p-methoxyphenylphosphine) copper(I) tetrahydroborate, (p-MeO-Ph3P)2Cu(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)2Cu(BH4) (1) the P–Cu–P bond angle of 132.45(2)° 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)° in (p-tolyl3P)2Cu(BH4) (2) and 121.51(5)° in (p-MeO-Ph3P)2Cu(BH4) (3). The arylphosphine analogs (p-tolyl3P)2Cu(BH4) (2) and (p-MeO-Ph3P)2Cu(BH4) (3) display intramolecular face-to-face π-stacking interactions between an aryl group from each coordinated phosphine, at centroid-to-centroid distances of 3.768(1) and 3.581(3) Å, respectively, while (p-MeO-Ph3P)2Cu(BH4) (3) also exhibits intermolecular edge-to-face π-stacking interactions.

X-ray crystal structures of bis(phosphine) copper(I) tetrahydroborate complexes reveal the coordination mode of the tetrahydroborate ligand. Different intramolecular π-stacking motifs between the arylphosphines are observed for the bis(triphenylphosphine) complex and the analogs derived from tris(p-tolyl)phosphine and tris(p-methoxyphenyl)phosphine.Figure optionsDownload as PowerPoint slide