1,2,4‐Triazol‐3‐ylidenes with an N‐2,4‐Dinitrophenyl Substituent as Strongly π‐Accepting N‐Heterocyclic Carbenes |
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| Authors: | Dr. Tetsuo Sato Yoichi Hirose Daisuke Yoshioka Tsubasa Shimojo Prof. Dr. Shuichi Oi |
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| Affiliation: | 1. Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, 6‐6‐11 Aramaki‐Aoba, Aoba‐ku, Sendai 980‐8579 (Japan), Fax: (+81)?22‐795‐5874;2. Environment Conservation Research Institute, Tohoku University, 6‐6‐11 Aramaki‐Aoba, Aoba‐ku, Sendai 980‐8579 (Japan) |
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| Abstract: | The synthesis and characterisation of a series of new Rh and Au complexes bearing 1,2,4‐triazol‐3‐ylidenes with a N‐2,4‐dinitrophenyl (N‐DNP) substituent are described. IR, NMR, single‐crystal X‐ray diffraction and computational analyses of the Rh complexes revealed that the N‐heterocyclic carbenes (NHCs) behaved as strong π acceptors and weak σ donors. In particular, a natural bond orbital (NBO) analysis revealed that the contributions of the Rh→Ccarbene π backbonding interaction energies (ΔEbb) to the bond dissociation energies (BDE) of the Rh? Ccarbene bond for [RhCl(NHC)(cod)] (cod=1,5‐cyclooctadiene) reached up to 63 %. The Au complex exhibited superior catalytic activity in the intermolecular hydroalkoxylation of cyclohexene with 2‐methoxyethanol. The NBO analysis suggested that the high catalytic activity of the AuI complex resulted from the enhanced π acidity of the Au atom. |
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| Keywords: | acidity carbene ligands gold ligand effects rhodium |
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