Reactivity ofN-trimethylsilyl-imidazole and 2-methylimidazole; synthesis and physico-chemical studies on transition metal imidazolates and mixed ligand imidazolates

Abstract

N-trimethylsilylimidazole andN-trimethylsilyl-2-methylimidazole react with MCl2 yield [ML2] (M=Ni or Cu; L =imidazolate or 2-methylimidazolate). The complex [NiL2] can also be prepared from [Ni(Ph3P)2Cl2]; [Cu(Ph3P)3Cl] yields [Cu(Ph3P)2L]. The complexes are soluble in most non-polar organic solvents and experimentally determined molecular weights suggest they are monomers in solution. Magnetic susceptibility measurements and reflectance and electronic spectral studies at room temperature are commensurate with square-planar geometry for [CuL2]. Although, the ligand field spectrum for [NiL2] is compatible with a square-planar geometry, the anomalous μeff value suggests that the ground electronic state of NiII in [NiL2] is near the magnetic cross-over point concomitant with the singlet-triplet spin state equilibrium. The i.r. spectra exhibit characteristic imidazolate and Ph3P ring vibrations, andv(M−N) andv(M−P) stretching vibrations at the appropriate frequencies. The synthesis and characterization of a CuII complex, formulated as [Cu(Ph3P)2LCl], with tetrahedral structure is described.