Organometallic dithiolene complexes of benzenedithiolate analogues with π-coordinating and π-interacting Cp* ligand

Organometallic dithiolene complexes, which were formulated as [Cp*M(dcbdt)] and [Cp*M(dcdmp)] (M = Co, Rh, Ir; Cp* = eta(5)-pentamethylcyclopentadienyl, dcbdt = 4,5-dicyanobenzene-1,2-dithiolate, dcdmp = 2,3-dicyano-5,6-dimercaptopyrazine) were prepared from a low valent Cp*Co-I or high valent Cp*M-III species (M-III = Co-III, Rh-III, Ir-III). The UV-Vis absorption spectral and electrochemical data of them were obtained. The lowest absorption (HOMO-LUMO) energies of them became redshift in order of the Co > Rh > Ir complexes. The reduction potentials suggested that the central metal modifies their LUMO levels. The molecular and crystal structures of [Cp*Co(dcbdt)] (3a), [Cp*Co(dcdmp)] (4a) and [Cp*Rh(dcdmp)] (4b) were determined by X-ray diffraction studies. The cobalt complexes 3a and 4a were monomeric, formally 16-electron complexes and have two-legged piano-stool geometries. The crystal structure of 3a indicated some plane-to-plane intermolecular interactions such as benzene center dot center dot center dot benzene interaction on the dcbdt ligand and two Cp*center dot center dot center dot benzene pi-pi stackings. 4a showed plane-to-plane interaction with a pseudo-4-fold-symmetry arrangement between the pyrazine moieties on the dcdmp ligand. The rhodium complex 4b was dimeric in the crystal to form a criss-cross arrangement and had a three-legged piano-stool geometry, but it was monomerized in solution. The dimer of 3b was observed in the oxidation process of the cyclic voltammogram. (C) 2009 Elsevier B.V. All rights reserved.