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Bonding Analysis of N‐Heterocyclic Carbene Tautomers and Phosphine Ligands in Transition‐Metal Complexes: A Theoretical Study
Author(s) -
Tonner Ralf,
Heydenrych Greta,
Frenking Gernot
Publication year - 2007
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200700235
Subject(s) - chemistry , phosphine , tautomer , lone pair , bond dissociation energy , carbene , ligand (biochemistry) , transition metal , sigma bond , crystallography , metal , bond energy , computational chemistry , dissociation (chemistry) , stereochemistry , chemical bond , molecule , organic chemistry , catalysis , biochemistry , receptor
DFT calculations at the BP86/TZ2P level were carried out to analyze quantitatively the metal–ligand bonding in transition‐metal complexes that contain imidazole (IMID), imidazol‐2‐ylidene (nNHC), or imidazol‐4‐ylidene (aNHC). The calculated complexes are [Cl 4 TM(L)] (TM=Ti, Zr, Hf), [(CO) 5 TM(L)] (TM=Cr, Mo, W), [(CO) 4 TM(L)] (TM=Fe, Ru, Os), and [ClTM(L)] (TM=Cu, Ag, Au). The relative energies of the free ligands increase in the order IMIDnNHC>IMID for the donor strength, which is in agreement with the progression of the metal–ligand bond‐dissociation energy (BDE) for the three ligands for all metals of Groups 4, 6, 8, and 10. The electrostatic attraction can also be decisive in determining trends in ligand–metal bond strength. The comparison of the results of energy decomposition analysis for the Group 6 complexes [(CO) 5 TM(L)] (L=nNHC, aNHC, IMID) with phosphine complexes (L=PMe 3 and PCl 3 ) shows that the phosphine ligands are weaker σ donors and better π acceptors than the NHC tautomers nNHC, aNHC, and IMID.