Reaction Mechanism of the C⋮N Triple Bond Cleavage ofβ-Ketonitriles on a Molybdenum(0) Center1

Abstract

The molybdenum dinitrogen complex trans-[Mo(N2)2(dppe)2] (2) reacted with 2−2.5 equiv of various β-ketonitriles at room temperature to afford the (nitrido)(nitrile-enolato) complexes trans-[Mo(N)(NCCR1COR2)(dppe)2] (4; R1 = H, R2 = 4-MeOCOC6H4, 4-ClC6H4, 4-Tol, 4-MeOC6H4, 2-C4H3O, 2-C4H3S, Pri; R1 = CN, R2 = Me, Ph; dppe = Ph2PCH2CH2PPh2) via the C⋮N triple bond cleavage of the nitriles on the molybdenum center. On the other hand, the reaction of complex 2 with 2 equiv of pivaloylacetonitrile at room temperature led to the isolation of the (alkylideneamido)(nitrile-enolato) complex trans-[Mo(NCHCH2COBut)(NCCHCOBut)(dppe)2] (5k), which further underwent the cleavage of the CN double bond of the alkylideneamido ligand to give the corresponding (nitrido)(nitrile-enolato) complex trans-[Mo(N)(NCCHCOBut)(dppe)2] together with 4,4-dimethyl-1-penten-3-one. Furthermore, treatment of 2 with large excess amounts of 4-chlorobenzoylacetonitrile followed by anion metathesis with [NHEt3][OTf] (OTf = OSO2CF3) resulted i...