Transformation of a methyleneamide ligand at molybdenum: electrochemical oxidation to a cyanide, reactions with elemental oxygen, sulphur or selenium and X-ray crystal structures of trans-[Mo(CN)Cl(dppe)2]·MeOH and trans-[Mo(NCS)Cl(dppe)2]; electroreduction of the cyanide to an aminocarbyne, trans-[Mo(CNH2)Cl(dppe)2](dppe = Ph2PCH2CH2PPh2)

Abstract

Deprotonation of the methylimide trans-[Mo(NMe)Cl(dppe)₂]⁺(dppe = Ph₂PCH₂CH₂PPh₂) gives the reactive methyleneamide trans-[Mo(NCH₂)Cl(dppe)₂]A; oxidation of A at a platinum anode or by iodine gives trans-[Mo(CN)Cl(dppe)₂]B, the structure of which has been determined by X-ray crystallography. Carbon-13 labelling studies suggest that the rearrangement of the MoNC framework to MoCN is intramolecular. Compound A reacts with chalcogens to give heterocumulene complexes trans-[Mo(NCX)Cl(dppe)₂]C(X = O, S or Se), and the X-ray crystal structure of the sulphur derivative shows that the NCS ligand is N-bonded as an isothiocyanate. The electrochemistry of compound B is extensive: reduction under N₂ gives trans-[Mo(N₂)(CN)(dppe)₂]^– and in the presence of phenol affords the isolable aminocarbyne trans-[Mo(CNH₂)Cl(dppe)₂].