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The reactions of INCO to IOCN, INCS to ISCN, and INCSe to ISeCN have been studied at the MP2/6-311++G(2df)//B3LYP/6-311++G(2df) level. Geometries of reactants, transition states, and products have been optimized, and geometries of transition states are reported for the first time. The reasons that INCO, ISCN, and ISeCN are easily detected instead of IOCN, INCS, and INCSe have been explained successfully. The breakage and formation of chemical bonds along the reaction paths have been discussed by the topological analysis method of electronic density. The calculated results show that there are two kinds of structure transition states (STS) in the reactions studied.

The σ-hole of M2 H6 (M = Al, Ga, In) and π-hole of MH3 (M = Al, Ga, In) were discovered and analyzed, the bimolecular complexes M2 H6 ···NH3 and MH3 ···N2 P2 F4 (M = Al, Ga, In) were constructed to carry out comparative studies on the group III σ-hole interactions and π-hole interactions. The two types of interactions are all partial-covalent interactions; the π-hole interactions are stronger than σ-hole interactions. The electrostatic energy is the largest contribution for forming the σ-hole and π-hole interaction, the polarization energy is also an important factor to form the M···N interaction. The electrostatic energy contributions to the interaction energy of the σ-hole interactions are somewhat greater than those of the π-hole interactions. However, the polarization contributions for the π-hole interactions are somewhat greater than those for the σ-hole interactions.

The metal−metal and metal−ligand bonds in a series of binuclear metallocenes (η 5 -C 5 H 5 ) 2 M 2 (M = Be, Mg, Ca, Ni, Cu, Zn) have been characterized within the framework of the atoms in molecules (AIM) theory, electron localization function (ELF), and molecular formation density difference (MFDD). The calculated results show that the metal−metal bonds in the binuclear main-group-metal metallocenes are different from those in binuclear transition-metal metallocenes. In binuclear maingroup-metal metallocenes, the metal−metal bonds are linked by two metal−"non-nuclear attractor (NNA)" bonds, while such NNAs do not exist in the binuclear transition-metal metallocenes. In addition, the transition-metal−transition-metal bonds are more delocalized than those of the main-group-metal−main-group-metal bonds. The main-group-metal−main-group-metal bonds show covalent characteristics while the transition-metal−transition-metal bonds display "closed shell" ionic characteristics. The metal−ligand bonds are mainly ionic. There are both σ and π characteristics in the metal−ligand interactions, and the π interaction is predominant.