The potential of Trivalent Phosphorus-based catalysts for pnicogen-bond activating

The catalytic power of trivalent phosphorus compounds (TPC) in order to activate the noncovalent interactions -particularly pnicogen-bonding [1]- was investigated. The Aza‒Diels‒Alder reaction [2] between a diene of 1, 3‒butadiene and the dienophiles of H2C=NNH2 and F2C=NNH2 were chosen to study. The catalytic effect of three different kinds of TPCs including PYnXm, where Y and X are H and Cl, respectively, n, m = 0, 1, 2, on the transition state (TS) of these reactions was studied. Geometry optimization of all the minima and TSs studied was carried out at the M062X-D3 level of theory with the TZVPP basis set [3,4]. Investigations showed that the PHCl2 catalyst is more capable of the pnicogen-bonding activating comparing to PHCl2 and PCl3 catalyst. In other words, the investigation of the catalytic effects of PH2Cl, PHCl2, and PCl3 on the TSs of the Aza‒Diels‒Alder reaction shows that the PHCl2 catalyst is of the most effects for lowering of the TS. Therefore, according to the obtained results, the orders of the catalytic effects of PH2Cl, PHCl2, and PCl3 on the TS studied in the present work are PHCl2 PCl3 PH2Cl, respectively. Corresponding TS energy values in the presence of the used catalysts for the dienophiles of H2C=NNH2 and F2C=NNH2 are 16.04, 16.74 for PHCl2, 17.16, 17.12 for PCl3 and 18.67, 18.06 for PH2Cl, respectively. Therefore, it could be concluded that the PHCl2 as the trivalent phosphorus-based catalyst is capable of the activation potential of pnicogen bonding in the Aza‒Diels‒Alder cycloaddition reactions with respect two other catalysts studied here.