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- Title
Platinum(II), palladium(II) and gold(I) benzimidazolin-2-ylidene as potential probes for determination of N-heterocyclic carbene donor strengths and steric bulks by DFT calculations.
- Authors
NGUYEN, VAN HA; DINH, THI HONG NGOC; DANG, THANH TUAN
- Abstract
Correlation between the donor strength of N-heterocyclic carbenes (NHC) and the M–Ccarbene bond distances in complexes of the type trans-[MX2(iPr2-bimy)(NHC)] (MX2 = PtCl2, PdBr2; iPr2-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) and [Au(iPr2-bimy)(NHC)]+ was investigated for a selection of 20 carbenes. The structures of the complexes were first optimized in gas phase. The bond lengths between metal (Pt, Pd and Au) and the carbene carbon of iPr2-bimy probe and NHC carbene under studied were then measured. Their correlation to the donor strength, evaluated using Huynh’s electronic parameter (HEP) was then examined. The results show good linear fitting between HEP value and Pd–Cprobe carbene distances or Hirchfeld atomic charge of the iPr2-bimy probe (Cprobe), suggesting the possibility of using theoretical approach for evaluation of donor strength for N-heterocyclic carbenes. In addition to the determination of NHC donicity, the optimized geometries can also be utilized as inputs for calculation of the steric properties, namely percent volume buried of the NHC ligands. Donor strength of N-heterocyclic carbene (NHC) ligands can be evaluated using theoretically optimized geometries for complexes of the type trans-[PdBr2(iPr2-bimy)(NHC)] (where iPr2-bimy probe is 1,3-diisopropyl benzimidazolin-2-ylidene). Correlation between Pd–Cprobe bond length and ligand L donor strength in Huynh’s electronic parameter (HEP) is expressed by the equation [dPt–Cprobe] = 0.00352 × [HEP] + 1.396 with correlation coefficient value of 0.97. Alternatively, HEP value can also be calculated from the Hirschfeld atomic charge on the iPr2-bimy carbene carbon atom (Cprobe) via the equation [Cprobe charge] = 0.00185 × [HEP] + 0.311.
- Publication
Journal of Chemical Sciences, 2020, Vol 132, Issue 1, p1
- ISSN
0974-3626
- Publication type
Article
- DOI
10.1007/s12039-020-01785-2