Experimental and theoretical examinations of n- sigma negative hyperconjugation in pyridinium dichlorophosphinomethylide

摘要

An X-ray crystal structure investigation as well as theoretical DFT (hybrid B3LYP/6-31G level) calculations of 2-ethylpyridinium dichlorophosphino-ethoxycarbonylmethylide confirm the existence of significant n->sigma negative (anionic) hyper-conjugation between the ylidic charge and the sigma_(P-Cl) bond in the most stable conformer,which has the phosphorus lone pair oriented orthogonally to the ylidic p_z orbital,resulting in elongation of the P-C1 bond parallel to the p- orbital but shortening of the C-P bond.