Synthesis and characterization of paramagnetic triazenido-complexes of rhenium(III). The crystal structure of [ReCl2(p-MeC6H4NNNC6H4Me-p)(PPh3)2]

Abstract

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 Re^III of the type [ReCl₂(RNNNR)(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.