An ab initio study of the complexes formed by hypohalous acids (HOX, X = F, Cl and Br) with formaldehyde has been carried out at the MP2/aug-cc-pVTZ computational level. Two minima complexes are found, one with an H...O contact and the other one with an X...O contact. The former is more stable than the latter, and the strength difference between them decreases as the size of the X atom increases. The associated HO and XO bonds undergo a bond lengthening and red shift, whereas a blue shift was observed in the bond of the hypohalous acid not involved in the interaction. The interaction strength and properties in both complexes are analyzed with atoms in molecules (AIM) and natural bond orbital (NBO) theories. The energy decomposition analyses indicate that the contribution from the electrostatic interaction energy is larger in the hydrogen-bonded complexes than that in the halogen-bonded complexes.

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A density functional theory study was performed to understand the detailed mechanisms of the cross-benzoin reactions catalyzed by N-heterocyclic carbene (NHC) species. Our theoretical study predicted that the first H-transfer operates with water in solution as a mediator, and the second H-transfer undergoes a concerted mechanism rather than a stepwise one. In addition, the chemoselectivity of the reactions studied in this work has been explored. P1 was obtained as a major product mainly due to the more stable intermediate formed by reaction of NHC with reactant R1. Different steric effects resulting from the fused six-membered ring in transition state TS7 and the fused five-membered ring in transition state TS13 are the origin leading to the chemoselectivity.

For C−H alkenylation of aryl-substituted diarylisoxazoles, one mode is N-directed C−H alkenylation and the other is C−H alkenylation in the isoxazole ring. In this study, selective C−H alkenylations of 3,5diarylisoxazoles have been investigated theoretically with the aid of density functional theory (DFT) calculations. With Cp*Rh III as the catalyst, the Ndirected C−H alkenylation is preferred as a result of the stronger interaction energy caused by the nitrogen-directing effect. With Pd(OAc) 2 as the catalyst and Ag 2 CO 3 as the cocatalyst, their combination switches the regioselectivity to the C−H alkenylation in the isoxazole ring. The strong structural distortion involved in the competing N-directed olefin insertion transition state was found to suppress N-directed C−H alkenylation. With Pd(OAc) 2 as the catalyst and Cu(OTf) 2 as the cocatalyst, the N-directed C−H alkenylation becomes preferred due to the strong coordination of the nitrogen atom to the copper center. In particular, the structural and mechanistic information involved in the above two heterodimetallic Pd/Ag and Pd/Cu catalytic systems will help toward understanding and designing novel relevant heterodimetalliccatalyzed reactions.

The stable structures of Ag–Au and Cu–Au clusters with 1 : 1, 1 : 3 and 3 : 1 compositions with up to 108 atoms are obtained using a modified adaptive immune optimization algorithm with Gupta potential. The dominant motifs of Ag–Au and Cu–Au clusters are decahedron and icosahedron, respectively. However, in Ag-rich Ag–Au clusters, more icosahedra are found, and in Cu-rich Cu–Au clusters, there exist several decahedral motifs. Four Leary tetrahedral motifs are predicted. Cu core Au shell configurations are predicted in Cu–Au clusters. In Ag–Au clusters, most Ag atoms are on the surface, but partial ones are located in the inner shell, while Au atoms are interconnected in the middle shell.