This critical review covers significant recent advances in the chemistry of pnictogen(III)-nitrogen ring systems, also known as cyclopnict(III)azanes. The synthetic methodologies and reactions of the heavier pnictogen systems are compared with the well-developed chemistry of cyclophosph(III)azanes. Particular attention is focused on ring-oligomerization processes and the use of four-membered E(2)N(2) rings as building blocks for the synthesis of macrocyclic molecules. Main-group element and transition-metal complexes are also discussed (95 references).

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The nature of weak interactions in dimers X3E•••EX3 (E = NBi, X = FI) was investigated by wave function and density functional-based methods. Out of the twenty systems studied, ten are found to be bound at the CP-MP2 and LMP2 levels of theory.Detailed partition of the interaction energy into different components revealed that dispersion is the primary force holding the dimers together but there also exist an important ionic component whose contribution increases with increasing halogen size. As expected, standard density functionals fail to describe bonding in the studied systems.However, the performance of DFT methods can be easily improved via empirical dispersion correction though full agreement with high level ab initio results was not obtained. Total binding energies calculated at the SCS-MP2 and LCCSD(T) levels of theory yield an energy scale of 1015 kJ mol 1 which compares to a weak hydrogen bond and demonstrates that E•••E interactions, and P•••P interactions in particular, can be considered relevant for determining molecular structure in the solid state. In addition to high-level energy estimates, results from detailed bonding analysis showed that group 13 dimetallenes are structural analogues of the studied dimers, and as such contain a slipped -interaction which is anti-bonding in nature.3