Structures of the phosphinidene germylenoid HP=GeLiF and its cycloaddition reaction with ethylene

Abstract

The structures of phosphinidene germylenoid HP=GeLiF were studied for the first time by using DFT (density functional theory) calculations. The geometries were optimized at the B3LYP/6-311+G (d, p) level at first and then the single-point energies were calculated at QCISD/6-311++G (d, p) level. Theoretical calculations predicted that HP=GeLiF has two equilibrium structures, the p-complex (1) and the three-membered-ring (2) structures, in which structure 1 has the lower energy and is more stable than 2. To exploit the reactivity of HP=GeLiF, the cycloaddition reaction of 1 and ethylene was investigated at the same level of theory. From the potential energy profile, we predicted that the cycloaddition reaction has one dominant reaction pathway. The calculated result shows that the dominant reaction pathway is a [2 + 2] cycloaddition reaction which is the interaction of two π bonds in HP=GeLiF and ethylene molecule, and a four-membered-ring P-heterocyclic germylene is formed. Since sp3 hybridization of Ge atom in this four-membered-ring germylene, it may further react with another ethylene and finally forming a spiro-Ge-heterocyclic compound involving phosphorus. This means that this reaction involves a [2 + 2] cycloaddition as the initial step, and then a [2 + 1] cycloaddition carried out.