A quantum-chemical and gas phase electron diffraction study of the structure of formylphosphine and acetyldimethylphosphine

The equilibrium geometry and energy and structural changes accompanying inversion motion in the phosphorus fragment and acyl group internal rotation in the H 2 PCHO and Me 2 PCMeO molecules were calculated by the MP2(full) method using basis sets from 6–31G( d , p ) to 6–311G(3 df , 2 p ). The structure of Me 2 PCMeO was determined by electron diffraction using the dynamic model of acyl group internal rotation based on the quantum-chemical potential function of torsional motion. Acylphosphines have amide-type equilibrium conformations with acyl groups rotated through ∼100° from their orientation in the C=O/PX 2 anti - form, where X = H, Me ( C 1 symmetry). Considerable pyramidality of the phosphorus fragment distinguishes the equilibrium structures of acylphosphines from amides with a planar molecular frame ( C s symmetry). The r h 1 geometric parameters of the Me 2 PCMeO molecule determined by electron diffraction closely agree with quantum-chemical estimates for the equilibrium configuration.