Experimental and theoretical studies show that all covalent azides possess a nonlinear azide group. They also rationalize this remarkable structural feature. We have seen that the most important non-covalent contributions in the covalently bound azides system (X-N1-N2-N3) are the π-delocalization over the entire molecule and a strong negative hyperconjugation which donates electron density from the filled σ (X-N1) orbital into the unfilled, antibonding π* (N2-N3) orbital. For transition metal

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... ide complexes, a bent configuration and a small difference between the N-N bond lengths, generally the longer one being adjacent to the transition metal, were observed.