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How to capture C2O2: structures and bonding of neutral and charged complexes [(NHC)-C2O2-(NHC)]q (NHC = N-heterocyclic carbene; q = 0, 1+, 2+).
Ding, Chengxiang; Yao, Lei; Zhao, Lili; Frenking, Gernot.
Afiliação
  • Ding C; Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 211816, China.
  • Yao L; Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 211816, China.
  • Zhao L; Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 211816, China.
  • Frenking G; Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, China. ias_llzhao@njtech.edu.cn.
Phys Chem Chem Phys ; 24(27): 16732-16745, 2022 Jul 13.
Article em En | MEDLINE | ID: mdl-35770713
ABSTRACT
We present the results of DFT calculations and a thorough bonding analysis of the neutral and charged complexes of the elusive C2O2 species stabilized by two NHC ligands. It is shown that the thermodynamic stability of the neutral complex [(NHC)-C2O2-(NHC)] is due to the low-lying triplet state of [NHC-CO] (T), which is only 3.2 kcal mol-1 higher in energy than the singlet state [NHC-CO] (S), while the triplet state of CO is 131.9 kcal mol-1 above the singlet. The much lower S/T gap of [NHC-CO] than in CO comes from the charge donation of NHC into the degenerate π* LUMO of CO and the concomitant mixing of the LUMO of NHC with the degenerate π* LUMO of CO, which strongly lowers the energy difference between HOMO and LUMO in the complex. The energy gain resulting from the formation of the CC double bond compensates the singlet-triplet gap and the thermodynamic instability of the fragments [NHC-CO] (S). The dissociation of neutral [(NHC)-C2O2-(NHC)] to 2NHC and 2CO molecules is calculated to be endothermic by Do = 78.2 kcal mol-1. The bonding analysis indicates that the neutral and the charged molecules [(NHC)-C2O2-(NHC)]q have a central unit with C-C single bonds, where a combination of electron sharing and s dative interactions leads to very strong carbon-carbon bonds complemented by minor π-donation, which make all systems stable with respect to dissociation reactions. The central C2O2 fragment carries a large negative partial charge in the neutral and singly charged compounds [(NHC)-C2O2-(NHC)]0,1+, while it is neutral in the dication [(NHC)-C2O2-(NHC)]2+.

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: Phys Chem Chem Phys Assunto da revista: BIOFISICA / QUIMICA Ano de publicação: 2022 Tipo de documento: Article País de afiliação: China

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: Phys Chem Chem Phys Assunto da revista: BIOFISICA / QUIMICA Ano de publicação: 2022 Tipo de documento: Article País de afiliação: China