MOLECULAR-STRUCTURES AND CRYSTAL-STRUCTUR ES OF 2 MONONUCLEAR RUTHENIUM(II) COMPLEXES WITH THE STRONGLY PI-ACCEPTING LIGAND 2,2'-AZOBIS(PYRIDINE) (ABPY) - [MER-RU(ABPY)(3)](PF6)(2) AND RU(ABPY)(2)CL-2 (CTC ISOMER)
J. Fees et al., MOLECULAR-STRUCTURES AND CRYSTAL-STRUCTUR ES OF 2 MONONUCLEAR RUTHENIUM(II) COMPLEXES WITH THE STRONGLY PI-ACCEPTING LIGAND 2,2'-AZOBIS(PYRIDINE) (ABPY) - [MER-RU(ABPY)(3)](PF6)(2) AND RU(ABPY)(2)CL-2 (CTC ISOMER), Zeitschrift fur Naturforschung. B, A journal of chemical sciences, 50(1), 1995, pp. 15-22
Crystal structure analyses of the title complexes have been carried ou
t in order to establish their molecular configurations. The tris(chela
te) complex dication in (1)(PF6)(2) exhibits a mer configuration of py
ridine and azo nitrogen atoms in an approximately octahedral arrangeme
nt at the metal. The dichlororuthenium bis(chelate) compound 2 has the
halide ligands and the coordinated azo nitrogen centers in an equator
ial cis arrangement whereas two pyridyl groups (one of each abpy ligan
d) occupy the axial positions. The bond distances from the metal to th
e nitrogen donor centers are systematically smaller for the stronger p
i accepting azo functions than for the more basic but less pi acidic p
yridyl groups, a result which differs from that obtained for Mo(0) and
Cu(I) complexes of abpy. All Ru-N distances are shorter in the neutra
l dichloro complex 2. The non-coordinated pyridyl rings of the potenti
ally tetradentate abpy ligands are tilted into approximate s-cis/(NN-t
rans)/s-trans positions (dihedral angle omega approximate to 145 degre
es) as to minimize steric repulsion. however, they do not coordinate t
o the metal (d(Ru-N) > 327 pm). While there are no significant intermo
lecular interactions, the observed conformation implies that considera
ble structural reorganization is necessary for the formation of oligon
uclear complexes.