Nickel‐Molybdenum and Nickel‐Tungsten Dithiolates: Hybrid Models for Hydrogenases and Hydrodesulfurization

The heterobimetallic complexes [(dppe)Ni(pdt)Mo(CO)(4)], [(dcpe)Ni(pdt)Mo(CO)(4)], [(dppe)Ni(pdt)W(CO)(4)] and [(dcpe)Ni(pdt)W(CO)(4)] {dppe = Ph2P(CH2)(2)PPh2; dcpe = Cy2P(CH2)(2)PCy2; pdt(2-) = S-(CH2)(3)S-} have been prepared and structurally characterized. The internuclear separation in these (NiM0)-M-II species is highly sensitive to diphosphine basicity and is smallest in the dppe complexes wherein the planar Ni centres are electron-poor and require interaction with the group 6 metal. The (NiW0)-W-II species [(dppe)Ni(pdt)W(CO)(4)] was converted into its stable conjugate acid [(dppe)Ni(pdt)HW(CO)(4)](+), a rare example of a nickel-tungsten hydride. This (NiHWII)-H-II complex is an electrocatalyst for H+ reduction and is relevant to both biological and synthetic H-2-processing catalysts.