Stereoisomerism of oxotrichlorobis(triphenylphosphine)rhenium(V), ReOCl 3 (PPh 3 ) 2 : a reinvestigation

Abstract

The various preparative procedures described in the literature for ReOCl 3 (PPh 3 ) 2 were repeated. The standard methods were found to yield a yellow triclinic material ([Formula: see text] a = 11.793, b = 14.300, c = 16.422 Å, α = 64.04°, β = 84.31°, γ = 87.32°, R = 0.064). The unit cell contains three discrete monomeric molecules with the trans-bis(phosphine) configuration, one of which has its Cl-Re=O unit disordered over two opposite directions. Recrystallization in CH 2 Cl 2 yielded crystals of the bright green monoclinic polymorph (C2/c, a = 24.347, b = 9.604, c = 15.666 Å, β = 116.77°, R = 0.025) containing the same monomeric molecule, but with a different conformation of the PPh 3 ligands and a different packing pattern. These two polymorphs actually correspond to "isomers" 1 and 2 described by Johnson, Lock, and Wilkinson in 1964. Attempts to prepare their third "isomer" yielded powders containing ReOCl 3 (PPh 3 ) 2 (green polymorph) and ReNCl 2 (PPh 3 ) 2 . The IR and 31 P NMR spectra of these samples are discussed.