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.