Monometallic, homo- and hetero-bimetallic complexes based on redox active tris(3,5-dimethylpyrazolyl)borato molybdenum and tungsten nitrosyls. Part 6. Synthesis and electrochemistry of complexes containing saturated heterocyclic amide ligands. X-Ray crystal and molecular structure of [{Mo(NO)[HB(Me2pz)3]Cl}2(NC4H8N)]

Abstract

The co-ordinatively unsaturated complexes [M(NO){HB(Me₂pz)₃}Cl(Y)][M = Mo or W; Y = NC₃H₆^–, NC₄H₈^–, or NC₅H₁₀^–; HB(Me₂pz)₃= hydrotris(3,5-dimethylpyrazolyl)borate] have been prepared and characterised. All exhibit reversible one-electron reduction processes in their cyclic voltammograms. The bimetallic species [{M(NO)[HB(Me₂pz)₃]Cl}₂(NC₄H₈N)](M = Mo or W) were also prepared, and the molybdenum complex structurally characterised by an X-ray diffraction study which revealed a chair conformation for the bridging piperazine-1,4-diyl ligand (NC₄H₈N). The molybdenum atoms are oriented essentially equatorially with Mo ⋯ Mo separation 6.773(2)Å. These bimetallic species appear to behave as ‘strongly interacting’ redox systems. In the case of M = Mo two one-electron reduction processes, separated by 560 mV, were observed by cyclic voltammetry.