Reactions of dianionic carbonylmetalates with heteroallenes: Reduction of carbonyl sulfide, isothiocyanates, isocyanates, and carbodiimides by group 6 and 8 carbonylmetalates

Article abstract of DOI:10.1021/om00108a027

Dianionic carbonylmetalates of the group 6 and group 8 metals can reduce a number of heteroallenes X=C=Y to coordinated O≡X ligands, provided X is a first-row element (N or O) which can form a strong triple bond with C. Thus Na₂[M(CO)₄] (M = Fe, Ru) and Na₂[M(CO)₅] (M = Cr, W) react readily with COS to give [M(CO)₅] (M = Fe, Ru) and [M(CO)₆] (M = Cr, W) in good yield, as established by absorbance mode IR for Fe and W and by isolation of the known derivatives [M(CO)₄I₂] (M = Fe, Ru) and [N(n-Bu)₄][M(CO)₅Br] (M = Cr, W), while CS₂ does not give thiocarbonyl complexes with Na₂[W(CO)₅] or Na₂[Fe(CO)₄]. It is suggested on the basis of IR and stoichiometry that the COS reductions are reductive disproportionations leading to thiocarbonate formation. Isothiocyanates RNCS (R = Ph, Me) give moderate yields of the corresponding isonitrile complexes [M(CO)₄(CNR)] with Na₂[Fe(CO)₄], but not with Na₂[Ru(CO)₄]. A similar reaction of PhNCS with Na₂[Cr(CO)₅] gives low yields of [Cr(CO)₅(CNPh)], but [W(CO)₅(CNPh)] can only be isolated after addition of oxalyl chloride to the intermediate isothiocyanate complex. Reduction of PhNCO with Na₂[W(CO)₅] leads to 84% and 5% solution yields of [W(CO)₆] and [W(CO)₅(CNPh)], respectively, consistent with control of the reduction of unsymmetrical heteroallenes by the relative triple bond strengths in the product C≡X ligands (C≡O > C≡N > C≡S).