EDA-NOCV Analysis of Donor-Base-Stabilized Elusive Monomeric Aluminum Phosphides [(L)P-Al(L'); L, L' = cAACMe, NHCMe, PMe3

Abstract

Herein, we report on the stability and bonding analysis of donor-base-stabilized monomeric AlP species (1–6) of the general formula (L)P–Al(L′); [L = cAACMe, L′ = cAACMe, NHCMe, PMe3, (NiPr2)2 (1–4); L = L′ = NHCMe, PMe3 (5 and 6); cAAC = cyclic alkyl(amino) carbene; NHC = N-heterocyclic carbene]. Energy decomposition analysis coupled with natural orbitals for chemical valence (EDA-NOCV) analysis indicates the synthetic viability of this class of species, stabilized in their singlet ground state, in the laboratory. The CL–P bond is found to be a partial double bond (WBI ∼ 1.45), while the CL/PL–Al bond is a single bond (WBI ∼ 0.42–0.69). These bonds are mostly covalent or dative σ/π bonds depending upon the ligands attached. The central P–Al bond is an electron-sharing covalent polar single bond (WBI ∼ 0.80; P–Al) for 1–4 and a dative σ bond for 5 and 6 (WBI ∼ 0.89–0.93; P–Al). The calculated intrinsic interaction energies of the central P–Al bonds are found to be in the range from −116 to −216 kcal/mol (1–3 and 5 and 6). This value is the highest for compound 3, possibly due to the push and pull effects from the ligands PMe3 and cAAC, respectively.