Musso JV, Benedikter MJ, Wang D, Frey W, Altmann HJ, Buchmeiser MR. Reversible N-Heterocyclic Carbene-Induced α-H Abstraction in Tungsten(VI) Imido Dialkyl Dialkoxide Complexes.
Chemistry 2020;
26:8709-8713. [PMID:
32202338 PMCID:
PMC7496809 DOI:
10.1002/chem.202000840]
[Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Indexed: 01/19/2023]
Abstract
The first reversible N‐heterocyclic carbene (NHC) induced α‐H abstraction in tungsten(VI) imido‐dialkyl dialkoxide complexes is reported. Treatment of W(NAr)(CH2Ph)2(OtBu)2 (Ar=2,6‐dichlorophenyl, 2,6‐dimethylphenyl, 2,6‐diisopropylphenyl) with different NHCs leads to the formation of complexes of the type W(NAr)(CHPh)(NHC)(CH2Ph)(OtBu) in excellent isolated yields of up to 96 %. The highly unusual release of the tert‐butoxide ligand as tBuOH in the course of the reaction was observed. The formed alkylidene complexes and tBuOH are in an equilibrium with the NHC and the dialkyl complexes. Reaction kinetics were monitored by 1H NMR spectroscopy. A correlation between the steric and electronic properties of the NHC and the reaction rates was observed. Kinetics of a deuterium‐labeled complex in comparison to its non‐deuterated counterpart revealed the presence of a strong primary kinetic isotope effect (KIE) of 4.2, indicating that α‐H abstraction is the rate‐determining step (RDS) of the reaction.
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