Synthesis and Structure of Metal Complexes of P‑Stereogenic Chiral Phosphiranes: An EDA-NOCV Analysis of the Donor–Acceptor Properties of Phosphirane Ligands

Reaction of the enantiomerically enriched P-stereogenic phosphiranes syn-(RP,SC)-Mes*PCH2CH­(Ph) (syn-1) and anti-(SP,SC)-Mes*PCH2CH­(Ph) (anti-2, Mes* = 2,4,6-(t-Bu)3C6H2) with metal complex precursors gave Au­(L)­(Cl) (L = 1 (3); L = 2 (4)), trans-ML2Cl2 (L = 1, M = Pd (5), Pt (6)), Pd­(η3-C3H5)­(L)­(Cl) (L = 1 (7)), and trans-RhL2(CO)­(Cl) (L = 1 (8); L = 2 (9)); 3, 4, 7, and 9 were crystallographically characterized. Phosphirane coordination resulted in shortening of the P–C bonds and increased bond angles at P, consistent with rehybridization at phosphorus. A comparison of complexes of phenylphosphirane and phenyldimethylphosphine using IR spectra, coupled with DFT studies using electronic decomposition analysis (EDA) and natural orbitals for chemical valence (NOCV), indicated that phosphiranes are slightly poorer σ-donors than the analogous phosphines and that the π-acceptor properties of these ligands are similar. Pauli repulsion, dispersion, and electrostatic attraction are also important factors in determining the strength of these metal–ligand interactions.