Computational design of intermolecularly stabilized cyclic compounds with low-valent phosphorus

Understanding the structure, bonding, and stability of the P^I compounds has continued to be one of the very important research areas of low-valent main group chemistry. Up to now, many intramolecularly stabilized P^I in cyclic form and several intermolecularly stabilized P^I in acyclic form have been reported. In this paper, we report the computational design of two novel cyclic intermolecularly stabilized P^I types, i.e., RP(μ-R)AlR₂ 1 and P(μ-R)₂AlR₂ 2. For most of the 26 kinds of the studied substituents, both types of the P^I structures are more stable than the classical P^III-one R₂P-AlR₂ 3. The P^I feature is supported by the structural, natural bond orbital analysis, and reactivity analysis. Formally, 1 and 2 are cooperatively stabilized by two sets of intermolecular donor–acceptor interactions between AlR₃ and PR, i.e., μ-R → P and P → Al in 1 and μ-R₁ → P and μ-R₂ → Al in 2. These novel P^I compounds strongly welcome the future laboratory studies.