Mitigating repulsions in close quarters: Copper tells us how

• Published in: Polyhedron Vol. 26; no. 1; pp. 142 - 148
• Main Authors: Ahuja, Ritu, Nethaji, M., Samuelson, A.G.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 02.01.2007
• Subjects: Cambridge Structural Database (CSD) analysis; Copper; Diphosphinoamine; Metal–metal interactions; Short bite ligand; Unsymmetrical coordination; Unsymmetrical coordination; Copper; Cambridge Structural Database (CSD) analysis; Diphosphinoamine; Short bite ligand; Metal–metal interactions
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2006.08.004

Destabilization due to d 10–d 10 repulsion in structurally characterized copper(I) diphosphinoamine (PPh 2) 2N(R) (R = H; dppa, R = i Pr; dppipa) dimers such as [Cu 2(dppa) 2(CH 3CN)(H 2O)(OClO 3)]ClO 4 ( 1), is mitigated by charge transfer interaction promoted by unsymmetrical coordination. Cambridge Structural Database studies support the proposition. Four copper(I) complexes of short bite ligands, bis(diphenylphosphino)amine (dppa) and bis(diphenylphosphino)isopropylamine (dppipa) were synthesized from appropriate precursors. All complexes were characterized by single crystal X-ray crystallography and spectroscopic techniques. In each of these complexes, two filled shell cations are forced into close proximity (≈2.7–2.8 Å). With no strong π acid ligands to siphon electron density from the filled d shell, the unavoidable repulsive d 10–d 10 interaction is mitigated when an unsymmetrical coordination environment around the copper atoms exists. The coordinatively saturated copper ion functions as a donor to the coordinatively unsaturated copper. A Cambridge Structural Database (CSD) search reveals the greater propensity of clusters with short contacts to adopt unsymmetrical coordination.