N-inversion and C–N rotational barriers in HX=CH-NH 2 (X=N,P,As) compounds: an ab initio study

Abstract

Ab initio calculations at HF/6-31G* and MP2/6-31G* levels are performed on methanimidamide, 1-phosphinidene methanamine and 1-arsenidene methanamine in their E and Z conformations. All of them are found to have pyramidal arrangement around nitrogen of the amino group. Pyramidalization in the amino group could be identified only after including electron correlation. The N-inversion barrier and the C–N rotational barriers in these molecules have been calculated to understand the electron distribution in these molecules. The C–N bond length decreases, bond strength increases, N-inversion barrier decreases, C–N rotation barrier increases, flow of charge from N to X increases in the order methanimidamide<1-phosphinidene methanamine<1-arsenidene methanamine. It is found that the electronegativity of X can not be taken as the driving force for the delocalization of electrons onto the π framework of the HX=C(H)-NH 2molecules.