Coinage Metal Complexes of Bis(quinoline-2-ylmethyl)phenylphosphine-Simple Reactions Can Lead to Unprecedented Results

The different coordination behavior of the flexible yet sterically demanding, hemilabile P,N ligand bis(quinoline-2-ylmethyl)phenylphosphine (bqmpp) towards selected Cu-I, Ag-I and Au-I species is described. The resulting X-ray crystal structures reveal interesting coordination geometries. With [Cu(MeCN)(4)]BF4, compound 1 [Cu-2(bqmpp)(2)](BF4)(2) is obtained, wherein the copper(I) atoms display a distorted square planar and square pyramidal geometry. The steric demand and pi-stacking of the ligand allow for a short Cu...Cu distance (2.588(9) angstrom). Cu-I complex 2 [Cu4Cl3(bqmpp)(2)]BF4 contains a rarely observed Cu4Cl3 cluster, probably enabled by dichloromethane as the chloride source. In the cluster, even shorter Cu...Cu distances (2.447(1) angstrom) are present. The reaction of Ag[SbF6] with the ligand leads to a dinuclear compound (3) in solution as confirmed by P-31{H-1} NMR spectroscopy. During crystallization, instead of the expected phosphine complex 3, a tris(quinoline-2-ylmethyl)bisphenyl-phosphine (tqmbp) compound [Ag-2(tqmbp)(2)](SbF6)(2) 4 is formed by elimination of quinaldine. The Au(I) compound [Au-2(bqmpp)(2)]PF6 (5) is prepared as expected and shows a linear arrangement of two phosphine ligands around Au-I.

Automated summary

The coordination behavior of a flexible and sterically demanding ligand (bqmpp) with Cu-I, Ag-I, and Au-I species was investigated. The X-ray crystal structures revealed interesting coordination geometries, including distorted square planar and square pyramidal geometries for Cu(I) compounds and the presence of Cu4Cl3 clusters in one of the complexes.