Synthesis and crystal structure of a new isomer of the μ-oxo-bis[dichlorooxobis(pyridine)rhenium(V)] complex {OReCl2py2}2O

Refluxing the oxo-alkoxo complexes ReO(OR)Cl(2)py(2) (where R = CH3 and C2H5) in toluene yielded an ore-bridged dinuclear compound {OReCl(2)py(2)}(2)O, in which a trans,trans arrangement of pyridine and chloride ligands around rhenium was determined by an X-ray diffraction study. This compound contains the same linear O=Re-O-Re=O backbone as the cis,cis isomer first prepared by Wilkinson's group, and the two ReCl2N2 planes are rotated with respect to each other by 27 degrees about the backbone axis. Both stereoisomers are green, they exhibit very similar infrared and C-13 NMR spectra, but they can be distinguished from their H-1 NMR chemical shifts. An X-ray diffraction study on ReO(OCH,)Cl,py, showed the presence of a trans,trans octahedral geometry around the metal and a bent Re-O-CH3 group (156 degrees). (C) 1998 Elsevier Science S.A. All rights reserved.