Is the phosphaethynolate anion, (OCP)−, an ambident nucleophile? A spectroscopic and computational study

Abstract

The reactivity of Na(OCP) was investigated towards triorganyl compounds of the heavier group 14 elements (R₃EX R = Ph or ⁱPr; E = Si, Ge, Sn, Pb; X = Cl, OTf). In the case of E = Si two constitutional isomers were formed and characterised in situ: R₃Si–O–CP is the kinetic and R₃Si–PCO is the thermodynamic product, representing experimental evidence of the ambident character of the (OCP)⁻ anion. Applying theoretical calculations and spectroscopic methods, the compound previously reported as ⁱPr₃Si–O–CP can now unambiguously be identified as ⁱPr₃Si–PCO. The heavier analogues form exclusively the phosphaketene isomer R₃E–PCO (E = Ge, Sn, Pb). DFT calculations were performed to gain deeper insight into the bonding and thermodynamic stability of these compounds.