SYNTHESIS, CHARACTERIZATION AND MOLECULAR-STRUCTURE OF THE 1-METHYLIMIDAZOLIUM CARBONYL-1-METHYLIMIDAZOLETETRACHLORORUTHENATE(III)

The complex M-ImH[RuCl4(CO)(M-Im)], where M-Im = 1-methylimidazole = C4N2H6, was synthesized and found to crystallize in the space group P2(1)/n, with a = 7.631(2), b = 10.832(3), c = 19.389(4) angstrom, beta = 91.52-degrees and Z = 4. The structure was solved from 1600 independent reflections with I > 3sigma(I) by Patterson and difference Fourier techniques and refined to R = 0.038. The Ru(III) ion is octahedrally coordinated to four co-planar chlorine atoms, the carbon atom of a CO group and a nitrogen of an M-Im ring. Another protonated M-Im group, which forms the counter-cation completes the crystal structure. The UV-Vis absorption spectrum shows two bands (316 and 442 nm) associated with ligand-to-metal charge transfer transitions and a third band at lower energy (530 nm) was assigned to a d-d transition. Room and liquid nitrogen temperatures EPR data confirmed the presence of the paramagnetically active Ru(III) and is consistent with the slightly distorted local C4v symmetry of the complex. The position of the stretching CO band is discussed in terms of metal-CO backbonding. The EPR data, measured at two frequencies (X and Q bands) show a rhombic distortion in the structure of the complex.