Synthesis, X-ray structure, and theoretical studies of novel cationic mono-cylopentadienyl complexes of Co(III): the orthometalation of trans-azobenzene

New cationic mono-cyclopentadienyl complexes of Co(III) containing mono or bidentate nitrogen donor ligands of general formula [Co(eta (5)-C5H5)(PPh3) L-2][BF4](2) (L = NC-CH3, 2, and NC = Ph, 3) or [Co(eta (5)-C5H5)(PPh3)(L-L )[BF4](2), [L-L = 2,2 ' -bisimidazole (H(2)biim) (4) and dipyridylamine [HN (NC5H5)(2)] (5) have been synthesised by the stoichiometric reaction of the Co(III) complex Co(eta (5)-C5H5)(PPh3)I-2 (1), with Ag[BF4] and the approp riate ligand in CH2Cl2. Under the same conditions and using;trans-azobenzen e as a ligand, an orthometalation reaction took placet giving the new compo und [Co(eta (5)-C5H5)(PPh3)(kappa -C,kappa -N-C6H4N=NPh)][BF4] (6) in high yield. The structural characterisation of compounds 4 and 6, and of the sta rting compound Co(eta (5)-C5H5)(PPh3)I-2 (1) was done by single-crystal X-r ay diffraction studies. DFT calculations (ADF program) were performed in or der to understand the orthometallation reaction. (C) 2001 Elsevier Science B.V. All rights reserved.