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Variable coordination of amine functionalised N-heterocyclic carbene ligands to Ru, Rh and Ir: C-H and N-H activation and catalytic transfer hydrogenation.
Dalton Trans. 2011 Oct 14; 40(38):9722-30.DT

Abstract

Chelating amine and amido complexes of late transition metals are highly valuable bifunctional catalysts in organic synthesis, but complexes of bidentate amine-NHC and amido-NHC ligands are scarce. Hence, we report the reactions of a secondary-amine functionalised imidazolium salt 2a and a primary-amine functionalised imidazolium salt 2b with [(p-cymene)RuCl(2)](2) and [Cp*MCl(2)](2) (M = Rh, Ir). Treating 2a with [Cp*MCl(2)](2) and NaOAc gave the cyclometallated compounds Cp*M(C,C)I (M = Rh, 3; M = Ir, 4), resulting from aromatic C-H activation. In contrast, treating 2b with [(p-cymene)RuCl(2)](2), Ag(2)O and KI gave the amine-NHC complex [(p-cymene)Ru(C,NH(2))I]I (5). The reaction of 2b with [Cp*MCl(2)](2) (M = Rh, Ir), NaO(t)Bu and KI gave the amine-NHC complex [Cp*Rh(NH(2))I]I (6) or the amido-NHC complex Cp*Ir(C,NH)I (7); both protonation states of the Ir complex could be accessed: treating 7 with trifluoroacetic acid gave the amine-NHC complex [Cp*Ir(C,NH(2))I][CF(3)CO(2)] (8). These are the first primary amine- or amido-NHC complexes of Rh and Ir. Solid-state structures of the complexes 3-8 have been determined by single crystal X-ray diffraction. Complexes 5, 6 and 7 are pre-catalysts for the catalytic transfer hydrogenation of acetophenone to 1-phenylethanol, with ruthenium complex 5 demonstrating especially high reactivity.

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Publisher Full Text (DOI)

Authors+Show Affiliations

Cross WB
Department of Chemistry, University of Leicester, UK. wbc2@le.ac.uk
Daly CG
No affiliation info available
Boutadla Y
No affiliation info available
Singh K
No affiliation info available

MeSH

AmidesAminesCatalysisChelating AgentsCrystallography, X-RayHeterocyclic CompoundsHydrogenationIridiumLigandsMethaneModels, MolecularMolecular StructureOrganometallic CompoundsRheniumRutheniumStereoisomerism

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

21858341

Citation

Cross, Warren B., et al. "Variable Coordination of Amine Functionalised N-heterocyclic Carbene Ligands to Ru, Rh and Ir: C-H and N-H Activation and Catalytic Transfer Hydrogenation." Dalton Transactions (Cambridge, England : 2003), vol. 40, no. 38, 2011, pp. 9722-30.
Cross WB, Daly CG, Boutadla Y, et al. Variable coordination of amine functionalised N-heterocyclic carbene ligands to Ru, Rh and Ir: C-H and N-H activation and catalytic transfer hydrogenation. Dalton Trans. 2011;40(38):9722-30.
Cross, W. B., Daly, C. G., Boutadla, Y., & Singh, K. (2011). Variable coordination of amine functionalised N-heterocyclic carbene ligands to Ru, Rh and Ir: C-H and N-H activation and catalytic transfer hydrogenation. Dalton Transactions (Cambridge, England : 2003), 40(38), 9722-30. https://doi.org/10.1039/c1dt10753d
Cross WB, et al. Variable Coordination of Amine Functionalised N-heterocyclic Carbene Ligands to Ru, Rh and Ir: C-H and N-H Activation and Catalytic Transfer Hydrogenation. Dalton Trans. 2011 Oct 14;40(38):9722-30. PubMed PMID: 21858341.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Variable coordination of amine functionalised N-heterocyclic carbene ligands to Ru, Rh and Ir: C-H and N-H activation and catalytic transfer hydrogenation. AU - Cross,Warren B, AU - Daly,Christopher G, AU - Boutadla,Youcef, AU - Singh,Kuldip, Y1 - 2011/08/22/ PY - 2011/8/23/entrez PY - 2011/8/23/pubmed PY - 2012/1/11/medline SP - 9722 EP - 30 JF - Dalton transactions (Cambridge, England : 2003) JO - Dalton Trans VL - 40 IS - 38 N2 - Chelating amine and amido complexes of late transition metals are highly valuable bifunctional catalysts in organic synthesis, but complexes of bidentate amine-NHC and amido-NHC ligands are scarce. Hence, we report the reactions of a secondary-amine functionalised imidazolium salt 2a and a primary-amine functionalised imidazolium salt 2b with [(p-cymene)RuCl(2)](2) and [Cp*MCl(2)](2) (M = Rh, Ir). Treating 2a with [Cp*MCl(2)](2) and NaOAc gave the cyclometallated compounds Cp*M(C,C)I (M = Rh, 3; M = Ir, 4), resulting from aromatic C-H activation. In contrast, treating 2b with [(p-cymene)RuCl(2)](2), Ag(2)O and KI gave the amine-NHC complex [(p-cymene)Ru(C,NH(2))I]I (5). The reaction of 2b with [Cp*MCl(2)](2) (M = Rh, Ir), NaO(t)Bu and KI gave the amine-NHC complex [Cp*Rh(NH(2))I]I (6) or the amido-NHC complex Cp*Ir(C,NH)I (7); both protonation states of the Ir complex could be accessed: treating 7 with trifluoroacetic acid gave the amine-NHC complex [Cp*Ir(C,NH(2))I][CF(3)CO(2)] (8). These are the first primary amine- or amido-NHC complexes of Rh and Ir. Solid-state structures of the complexes 3-8 have been determined by single crystal X-ray diffraction. Complexes 5, 6 and 7 are pre-catalysts for the catalytic transfer hydrogenation of acetophenone to 1-phenylethanol, with ruthenium complex 5 demonstrating especially high reactivity. SN - 1477-9234 UR - https://www.unboundmedicine.com/medline/citation/21858341/Variable_coordination_of_amine_functionalised_N_heterocyclic_carbene_ligands_to_Ru_Rh_and_Ir:_C_H_and_N_H_activation_and_catalytic_transfer_hydrogenation_ L2 - https://doi.org/10.1039/c1dt10753d DB - PRIME DP - Unbound Medicine ER -