Phosphine containing rhenium(III) carbonyl complexes. The crystal and molecular structure of tribromodicarbonylbis(dimethyl-phenylphosphine)rhenium(III)

Abstract

Bromine oxidation of [ReBr(CO) 3(PR 3) 2] [PR 3 = PMe 2Ph, PEt 2Ph, PMePh 2, PPh 3, PPh 2C 6H 4Me-4 or P(C 6H 4OMe-4) 3] yields stable seven-coordinate rhenium(III) complexes [ReBr 3(CO) 2(PR 3) 2] only for the less sterically demanding phosphines PMe 2Ph, PEt 2Ph and PMePh 2. Crystals of [ReBr 3(CO) 2(PMe 2Ph) 2] ( 1) are triclinic, space group P 1 − , Z = 2, in a unit cell with lattice parameters a = 9.575(8), b = 14.705(11), c = 9.629(12) Å, α = 77.71(7), β = 109.06(8) and γ = 115.02(8)°. 2991 independent reflections above background were collected on a diffractometer and refined to R0.07. The metal atom has a capped octahedral environment with a carbonyl in the unique capping position [1.87(3) Å], two phosphines [2.456(13), 2.496(11) Å] and one carbonyl 1.85(5) Å in the capped face, and three bromine atoms in the uncapped face [2.589(5), 2.623(6), 2.622(5) Å]. Attempts to convert ( 1) to the six-coordinate d 4 cation [ReBr 2(CO) 2(PMe 2Ph) 2] + for structural comparison with the isoelectronic Group 6 analogues [MBr 2(CO) 2(PR 3) 2] (M = Mo or W) were unsuccessful.