Crystal and molecular structure of di-µ-bromo-µ-tetraphenyldiphosphane-bis[tricarbonylrhenium(I)]

Abstract

The title complex has been prepared by treating P₂Ph₄ either with [ReBr(CO)₅] at the reflux temperature of benzene or with [Re₂Br₂(CO)₆(thf)₂](thf = tetrahydrofuran) at room temperature in toluene. Three-dimensional X-ray analysis has shown this to be the first example of a diphosphane bridging two co-ordination octahedra joined by a common edge. The substance crystallizes from toluene in the triclinic system, space group P, with cell constants a= 11.110(9), b= 11.538(9), c= 12.913(9)Å, α= 95.95(5), β= 102.54(5), γ= 95.92(5)°, and Z= 2. The molecule consists of two rhenium atoms linked by two bromine atoms and by a P–P bridge. The six carbonyl groups are distributed around the two rhenium atoms in two groups of three, each in a fac arrangement, thus completing the six-co-ordination. The normals to the planes defined by Re(1)–Br(1)–Br(2) and by the Re(2)–Br(1)-Br(2) intersect at an angle of 23.4°. Probably important P⋯Br interactions exist, as evidenced by the non-bonding distance of 3.49 Å observed, which is ca. 0.4 Å less than the van der Waals radii. The P–P bond is 2.308(6)Å. Evidence is presented that the products of formula [Re₂X₂(CO)₆(P₂Ph₄)](X = Cl or I) previously reported have structures probably similar to that of the present complex.