Effect of substituents on the molybdenum mediated carbonylation and methoxycarbonylation of dihaloalkynes

Dihaloalkynes of the type YCH(R)CCCH(R)Y (Y = Cl, Br, I; R = H or Me) or YCMe₂CCCMe₂Y were prepared from their diol precursors and reacted with Mo(CO)₃(phen)Y]⁻ (phen = 1,10-phenanthroline) in chlorinated solvent, methanol or water. Formation and stability of substituted products of the type Mo(CO)₂(η³-CH(R)C(COX)CCH(R))(phen)Y] (X = Y or X = OMe) were found to be dependent upon the nature of the halogen and degree of alkyl substitution of the alkyne. Reactions carried out in mixtures of methanol and ethers gave an alternative double addition product of the type Mo(CO)₂(η³-CH(R)C(CO₂Me)CC(OMe)(CH₂R))(phen)Y] for R = H, Y = Cl only.