Protonation and Lewis Acid-Base Equilibria in (Bipyrazine)Molybdenum and (Bipyrazine) Tungsten Tetracarbonyls

摘要

The title complexes react with boron trifluoride etherate to generate mono- and di-BF3 adducts. In H2SO4/ethanol solution one proton is coordinated. In each case reaction is assumed to occur at the peripheral uncoordinated nitrogen atoms of the bipyrazine unit. New metal to ligand charge transfer bands are observed for these various species. Analysis of the spectra shows that PKa(1) for the first uncoordinated nitrogen atom is about -0.3(Mo complex), and that extensive mixing of ground and excited states must be occurring to account for the oscillator strengths and bandwidths observed.