Generalized valence bond description of chalcogen-nitrogen compounds. II. NO, F(NO), and H(NO).

The electronic structure of the ground state of NO and those of F(NO) and H(NO), that is, the XNO and NOX isomers with X = F, H, were analyzed within the framework of generalized valence bond theory. In distinct contrast to the ground state of NS, it was found that the two-center, three-electron π interaction in NO(X(2)Π) is composed of a lone pair on O and a singly occupied orbital on N. Thus, F and H addition to NO preferentially leads to FNO and HNO. Somewhat surprisingly, the NOF and NOH isomers were found to be weakly bound, although for different reasons. The NOF state has a very unusual through-pair interaction with a NO-F bond length 0.444 Å longer than its covalent counterpart in OF(X(2)Π), while NOH arises from the N((2)D) + OH(X(2)Π) separated atom limit, similar to what we found for NSH.