Covalent and Ionic: Bonding Characteristics of HZnCH and ZnCH(2)and Their Interconversions

Wang E. Z. , Wang Y., Barnes E. C. , KAYA S.

CHEMISTRYSELECT, vol.5, no.37, pp.11410-11419, 2020 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 5 Issue: 37
  • Publication Date: 2020
  • Doi Number: 10.1002/slct.202002356
  • Title of Journal : CHEMISTRYSELECT
  • Page Numbers: pp.11410-11419


The structures of zinc carbene ZnCH(2)and zinc carbyne HZnCH, and the conversion transition states between them are optimized at B3LYP/aug-cc-pVTZ, MP2/aug-cc-pVTZ, and CCSD/aug-cc-pVTZ levels of theory. The thermodynamic energies with CCSD(T) method are further extrapolated to basis set limit through a series of basis sets of aug-cc-pVXZ (X=D, T, Q, 5). The Zn-C bonding characteristics are interpreted by molecular plots, Laplacian of density plots, the integrated delocalization indices, net atomic charges, and derived atomic hardness. On the one hand, the studies demonstrated the efficiency of DFT method in structure optimizations and the accuracy of CBS method in obtaining thermodynamic energies; On the other hand, the density analysis of CCSD/aug-cc-pVDZ density demonstrates that both the sharing interaction and ionic interaction are important in ZnCH(2)ad HZnCH. The(3)B(1)state of ZnCH(2)is the global minimum and formed in visible light, but its small bond dissociation energy (47.0 kcal/mol) cannot keep the complex intact under UV light (79.4-102.1 kcal/mol). However, the(3)sigma(-)state of HZnCH can survive the UV light due to the greater Zn-C dissociation energy (100.7 kcal/mol). The delocalization indices of Zn horizontal ellipsis C in both(3)B(1)of ZnCH2(0.777) and the(3)sigma(-)state of HZnCH (0.785) are close to the delocalization index of the single C-C bond of ethane (0.841), i. e. the nomenclature of Zinc carbene and Zinc carbyne is incorrect. The stronger Zn-C bond in the(3)sigma(-)state of HZnCH than in the(3)B(1)state of ZnCH(2)can be attributed to the larger charge separation in the former. It was found that the Zn-C bonds in related Zinc organic compounds were also single bonds no matter whether the organic groups are CR, CR2, or CR3. The ionic interactions were discussed in terms of the atomic hardness that were in turn related to ionization energy and electron affinity. The unique combination of covalent and ionic characteristics in the Zn-C bonds of organic Zinc compounds could be the origin of many interesting applications of organic Zinc reagents.