Topological effect on molecular orbitals

KSC = Kekule structure count QSAR = quantitative structure-activity relationships QSPR = quantitative structure-property relationships SRWAC = self-returning walk atomic code TEMO = topological effect on molecular orbitals TRE = topological resonance energy TREPE = TRE per r-electron. 

Abstract The agostic bond defines an intramolecular interaction where a a bond is geometrically close to an electron deficient centre (often a transition metal). The computational studies on this energetically weak interaction are reviewed and discussed. Various types of a bonds have been considered (C-H, C-C, Si-H, Si-C, B-H). It is suggested that a C-X bond in which X carries a lone pair should preferably not be viewed as agostic. The factors that contribute to his occurrence are discussed. In particular, the agostic interaction is very sensitive to steric effects. Explanations based on molecular orbital analysis, electron delocalization and topological analysis of the electron density are presented. 

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