Di-η5-cyclopentadienylmetal complexes with nitrogen donor atom ligands: New imidazole, N-methylimidazole,pyrazole and 2,2′-bisimidazole complexes of molybdenum and tungsten

Reactions of the tetrahedral metallocene derivatives M(η-C₅H₅)₂X₂], M(η-C₅H₅)₂HX] and M(η-C₅H₅)₂H₃]PF₆] (M = Mo, W; X = halogen) with ligands imidazole, N-methylimidazole, pyrazole and 2,2′-bisimidazole give a wide range of new mono- and bi-nuclear complexes. The pK_a values for some of the coordinated ligands and the ESR spectra of some molybdenum(V) complexes obtained by oxidation of their molybdenum(IV) analogues are also presented and discussed.