RHENIUM(V) OXO COMPLEXES WITH SCHIFF-BASE LIGANDS CONTAINING 4 OR 5 COORDINATION SITES - X-RAY MOLECULAR-STRUCTURE OF [NORMAL, NORMAL '-3-AZAPENTANE-1,5-DIYLBIS(SALICYLIDENEIMINATO)(3-)-O,O',N,N']OXORHENIUM(V)

The reactions of [ReOCl4]- with Schiff base ligands derived from salicylaldehyde and 1,5-diaminopentane (H2L1a), -hexane (H2L1b), -heptane (H2L1c) or diethylentriamine (H3L2) have been investigated. The complexes ReOCl2(EtOH)HL1n (I) (n = a, b or c), Re2O2(MeOH)2Cl4HL2 (II), ReOClL1n (III) and ReOL2 (IV), have been synthesized and characterized with the usual physicochemical measurements. The crystal structure of ReOL2 was determined by single crystal X-ray methods. Crystals are monoclinic, space group P2(1)/c, with a = 9.470(7), b = 9.358(8), c = 21.859(12) angstrom, beta = 99.23(8)-degrees and Z = 4. X-ray diffraction provides 5601 observed reflections (up to 2-theta = 60-degrees) and the structure has been refined by full-matrix least-squares methods to R = 0.061. The monomeric structure consists of distorted octahedral ReOL2 units. One oxygen atom of the N3O2 pentadentate ligand is located trans to the rhenium-oxo-oxygen bond, while the remaining four coordinating atoms lie on the equatorial plane of the octahedron assuming that the oxo-oxygen occupies an apex. The arrangement of the two iminophenolate groups is explained as a function of the length of the aliphatic chain joining the two imine groups.