Synthesis and characterization of paramagnetic triazenido-complexes of rhenium(III). the crystal structure of [reCl2(p-MeC6H4N-...N-...NC6H 4Me-p)(PPh3)2]

The compound [ReOCl3(PPh3)2] reacts with Li(RN3R) (R = p-MeC6H4,Ph, p-FC6H4, or p-ClC6H4) in boiling tetrahydrofuran to yield new complexes of ReIII of the type [ReCl2(RN-...N-...NR)(PPh3)2]. The i.r. spectra suggest that the organonitrogen ligand acts as a chelating ligand and that the two chlorine ligands are in cis position. Magnetic susceptibility measurements on the solids have demonstrated the presence of unpaired electrons, which affect the 1H n.m.r. spectra, the resonance signals being shifted up- and down-field with respect to SiMe4. The crystal structure of the title compound was determined by the X-ray analysis using counter data. The compound crystallizes in the monoclinic system, space group P21/a, with a = 14.50(1), b = 24.68(1), c = 12.91(1) Å, and β = 108.50(4)° for Z = 4. The structure was refined to R = 0.075. The rhenium atom is in a distorted octahedral co-ordination with two axial PPh3 groups, two cis-chlorine atoms, and the chelate ligand which forms a four-membered ring with the metal.