SYNTHESIS AND CHARACTERIZATION OF OXORHENIUM(V)-CATECHOLATE COMPLEXES- CRYSTAL AND MOLECULAR-STRUCTURES OF (CH3)4N[REO(O2C6H4)2] AND (CH3)4N[REO(PPH3)(O2C6H4)2].CH3OH

The reactions of ReOCl3(PPh3)2 with catechol and substituted catechols in methanol in the presence of triethylamine and tetramethylammonium chloride under N2 yield the green complexes [(CH3)4N]+[ReO(cat)2(PPh3) ]-(Cat = O2C6H4 (2), 4-CH3-O2C6H3 (3), O2C6Cl4 (4)). The reactions of 2 and 3 with pyridine in methylene chloride yield [(CH3)4N]+[ReO(cat)2 (py)]- (5) and [(CH3)4N]+[ReO(4-Me-cat)2(PY)]- (6). Variable temperatu re H-1 and P-31 NMR spectroscopy studies on these complexes indicate t hat the ancillary ligands (PPh3: 2, 3; py: 5, 6) undergo a dissociatio n-association process in solution along with concomitant cis-trans iso merization of the catecholate ligands. The reaction of [(CH3CH2)4N]+[R eO2(cat)2]- (8) with triphenylphosphine in refluxing ethanol yields th e reduced rhenium(V) square pyramidal complex [(CH3CH2)4N]+[ReO(cat)2] - (7) as an air and moisture-sensitive tan solid where triphenylphosph ine acts as a reducing agent. These complexes were characterized by el emental analysis, variable temperature H-1 and P-31 NMR spectroscopy a nd IR and UV-Vis spectroscopies. Complexes 2 and 7 were also character ized by_X-ray crystallography. Crystal data: C20H28NO5Re (2): tetragon al space group I4/m, a = 19.890(3), c = 10.438(2) A, V = 4129(2) A, Z = 8, D(calc) = 1.766 g CM-3; structure solution and refinement based o n 976 reflections (Mo Kalpha, lambda = 0.71073 angstrom) converged at R = 0.043. C36H43NO7PPe (7): monoclinic space group C2/c, a = 25.485(5 ) angstrom, b = 9.127(2), c = 30.590(6) angstrom, beta=101.84(3)-degre es, V = 6964(3) angstrom3, Z = 8, D(calc) = 1.563 g cm-3; 3298 reflect ions, R = 0.047.