Solid State Structures and Gold−Gold Bonding in Luminescent Halo(dimethylphenylphosphine)gold(I) Complexes

Abstract

The structures of the series of two-coordinate gold(I) complexes {(Me₂PhP)AuX}_n where X is Cl, Br, or I have been examined by X-ray diffraction. The chloro complex crystallized in two separate polymorphic forms. Colorless hexagonal blocks of {(Me₂PhP)AuCl}₃ crystallized in the monoclinic space group P2₁/m with a = 12.141(4) Å, b = 8.433(2) Å, c = 14.834(3) Å, and β = 94.15(2)° at 130 K with Z = 2. Refinement of 2837 reflections and 177 parameters yielded R = 0.066 and R_w = 0.069. The complex consists of three nearly linear P−Au−Cl units that are connected by Au−Au contacts at 3.091(2) and 3.120(2) Å. Colorless prisms of {(Me₂PhP)AuCl}₂ form in the orthorhombic space group P2₁2₁2₁ as described earlier (Cookson, P. D.; Tiekink, E. R. T. Acta Crystallogr. 1993, C49, 1602). The two nearly linear P−Au−Cl units are staggered and connected through a Au−Au bond (3.230(2) Å). Colorless rectangular prisms of {(Me₂PhP)AuBr}₂ form in the monoclinic space group P2₁ with a = 9.572(5) Å, b = 8.757(3), and c = 12.915(7) at 130 K with Z = 2. Refinement of 2469 reflections with 118 parameters yielded R = 0.080 and R_w = 0.084. {(Me₂PhP)AuI}₂ is isomorphous with the bromo complex with a = 9.736(2) Å, b = 8.890(2) Å, and c = 13.160(5) Å at 130 K with Z = 2. Refinement of 2796 reflections with 119 parameters yielded R = 0.052 and R_w = 0.058. These complexes are similar to the chloro dimer but with altered orientations of the phenyl substituent. The predicted order of ligand effects (Cl > Br > I) on Au−Au distances from quasi-relativistic calculations is borne out in the experimental values: 3.230 Å (Cl); 3.119 Å (Br); 3.104 Å (I). In dichloromethane, these complexes dissociate into monomeric units but there is some evidence for the presence of dimers in concentrated solutions of the iodide compound.