Binuclear copper(I) complexes containing bis(diphenylphosphino)methane bridging ligands: crystal structure of [Cu2(µ-dppm)2(MeCN)4][ClO4]2

Abstract

Novel binuclear copper(I) complexes of the types [Cu₂(µ-dppm)₂(MeCN)_n]X₂(n= 2 or 4) and [Cu₂(µ-dppm)₃]X₂(X = BF₄ or ClO₄, dppm = Ph₂PCH₂PPh₂) have been prepared. Proton and ³¹P-{¹H} n.m.r. studies at room temperature show that they undergo ligand-dissociation processes in solution. The crystal structure of [Cu₂(µ-dppm)₂(MeCN)₄][ClO₄]₂ has been determined by X-ray methods. Crystals are monoclinic, space group C2/c with Z= 4 in a unit cell of dimensions a= 22.407(9), b= 13.052(6), c= 21.522(8)Å, and β= 108.69(3)°. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares to R= 0.079 for 3 907 observed reflections [I > 3σ(I)]. The structure consists of [Cu₂(µ-dppm)₂(MeCN)₄]²⁺ cations and of disordered perchlorate anions. In the cations the two copper atoms are bridged by dppm ligands to give eight-membered Cu₂P₄C₂ rings. The tetrahedral co-ordination around the copper is completed by two nitrogen atoms from acetonitrile ligands.