Original scientific paper

Valence Bond Studies of the N-N Bonds of ONNO, ONNO₂, O₂NNO₂ and CH₂NNCH₂

Richard D. Harcourt ; The School of Chemistry, University of Melbourne, Parkville, Victoria 3052, Australia

Abstract

The results of some STO-5G valence bond calculations are presented for a cis ONNO component of each of ONNO2 and O2NNO2, and the CNNC component of trans CH2NNCH2. These studies provide support for the hypothesis that the -NO nitrogen atomic orbital, which is involved in the formation of the (fractional) N-N o bond of ONNO2, is primarily 2p in character, and oriented at right angles to the N-0 in ter nuclear axis, rather than along the N-N intemuclear axis. Whereas delocalization of oxygen lone-pair electrons into the atomic orbitals of the N-N o bond is responsible for the N-N bond lengthening for N2O4 relative to that of N2H4, the orientation and 2p character of the -NO nitrogen atomic orbital, as well as some delocalization of the oxygen lone-pair electrons, leads to the lengthening of the N-N bond of ONNO2. It has been shown previously (J. Mol. Struct. (Tkeochem) 206 (1990)
253) that repulsions between nitrogen lone-pair electrons, together with the nitrogen atomic orbital hybridization and orientation, are associated with the existence of a very long N-N bond in cis N2O2. These factors are calculated to operate in a different manner for the trans CNNC component of CH2NNCH2, for which the measured N-N bond length is essentially that of an N-N single bond.
Consideration is given to the construction and properties of increased- valence structures for ONON, ONONO2, two NO3 isomers, OSSO and S4, as well as for ONNO, ONNO2 and O2NNO2.

Keywords

Hrčak ID:

137313

URI

https://hrcak.srce.hr/137313

Publication date:

31.12.1991.

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