B3LYP, M06 and B3PW91 DFT assignment of nd 8 metal- bis -( N -heterocyclic carbene) complexes
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ORIGINAL PAPER
B3LYP, M06 and B3PW91 DFT assignment of nd8 metal-bis-(N-heterocyclic carbene) complexes Jean Moto Ongagna 1 & Aymard Didier Tamafo Fouegue 2 & Baruch Ateba Amana 1 & Gaël Mouzong D’ambassa 1 & Joseph Zobo Mfomo 3 & Luc Mbaze Meva’A 1 & Désiré Bikele Mama 1 Received: 17 April 2020 / Accepted: 3 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This paper is focused on the examination of the bonding properties of a series of [M(NHC)2X2] (M = nd8 transition metal; X = Cl, Br and I) complexes in normal, abnormal and mixed C∩C coordination modes. Structures have been optimised in gas phase using B3LYP, M06 and P3BW91 functionals. Two basis sets have been used: the LanL2DZ and a mixed basis set (LanL2DZ for nd8 transition metals as well as halogen atoms and 6-311+G(d,p) for other atoms). Results obtained indicate that the B3PW91 bond distances are closer to experimental data. The complexation energies obtained for each binding mode increase in the order: Ni2+ < Pd2+ < Pt2+, independently of the halogen atom adopted. From the Quantum Theory of Atoms in Molecule (QTAIM) approach, the instability has been found to follow this trend: M − X < M − C. The analysis of metal-ligand interactions using the natural bond orbital (NBO) revealed that the strongest metal-ligand interactions are observed in the normal binding mode. The NCH → MX2 donation terms were found to be interestingly predominant compared with back donation ones in the complexes studied, except in Pt chloride ones. The contribution of electrostatic interaction energy between the above fragments (ΔEelstat term) is in the range 57.48–63.95% traducing the fact that the interactions are mostly electrostatic. Keywords nd8-bis-NHC complexes . DFT . QTAIM . Charge decomposition analysis . Energy decomposition analysis
Introduction The study of catalytic systems involving transition metals for organic transformations has attracted great interest. For transition metal catalysis, the use of N-heterocyclic carbene (NHCs) as ligands has experienced a growing importance. Arduengo et al. [1–7] have isolated and characterised a Nheterocyclic carbene from the corresponding imidazolium Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00894-020-04500-7) contains supplementary material, which is available to authorized users. * Désiré Bikele Mama [email protected] 1
Computational and Theoretical Chemistry Unit, Department of Chemistry, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon
2
Department of Chemistry, Higher Teacher Training College Bertoua, University of Ngaoundere, P.O Box. 652, Bertoua, Cameroon
3
Department of Forestry and Wood Engineering, Advanced Training College for Technical Education, University of Douala, Douala, Cameroon
salts. These findings resulted in new classes of organic compounds which became thereafter an alternative to phosphines. Their diverse applications (pharmacy, fine chemistry, material science and polymer building bloc
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