STEREOISOMERISM OF OXOTRICHLOROBIS(TRIPHENYLPHOSPHINE)RHENIUM(V), REOCL3(PPH3)2 - A REINVESTIGATION

The various preparative procedures described in the literature for ReOCl3(PPh3)2 were repeated. The standard methods were found to yield a yellow triclinic material (P1BAR, a = 11.793, b = 14.300, c = 16.422 angstrom, alpha = 64.04-degrees, beta = 84.31-degrees, gamma = 87.32-degrees, 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 CH2Cl2 yielded crystals of the bright green monoclinic polymorph (C2/c, a = 24.347, b = 9.604, c = 15.666 angstrom, beta = 116.77-degrees, R = 0.025) containing the same monomeric molecule, but with a different conformation of the PPh3 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 ReOCl3(PPh3)2 (green polymorph) and ReNCl2(PPh3)2. The IR and P-31 NMR spectra of these samples are discussed.