Rhodium and iridium complexes of an asymmetric bicyclic NHC bearing secondary pyridyl donors

Newman, Paul David ORCID: https://orcid.org/0000-0002-1808-1211, Cavell, Kingsley John, Hallett, Andrew Jon and Kariuki, Benson ORCID: https://orcid.org/0000-0002-8658-3897 2011. Rhodium and iridium complexes of an asymmetric bicyclic NHC bearing secondary pyridyl donors. Dalton Transactions 40 (35) , pp. 8807-8813. 10.1039/C1DT10582E

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Abstract

A tridentate NCN ligand, 1, containing a bicyclic central NHC ring and two flanking pyridyl groups has been coordinated to Rh(I) and Ir(I) to give complexes of the type [M(κ3-1)(1,5-COD)]PF6 (2 M = Rh; 3 M = Ir). In contrast to our earlier study with this ligand, the complexes have been shown to approximate to a trigonal bipyramidal geometry in the solid state and exist as an isomeric mixture in solution as determined by 1H and 13C NMR spectroscopy. Electrochemical studies revealed that both complexes undergo a 1-electron oxidation with the potential of the Rh complex 0.1V less than that of the Ir complex in CH2Cl2. Preliminary DFT studies confirm the lowest energy conformations as those seen in the solid state and show the location and energy of the HOMOs to be identical in 2 and 3. Partial charge analysis shows a greater positive charge on the Ir in 3 compared to the Rh in 2. Some preliminary studies of hydrogenation reactivity have shown the complexes to be efficient for both transfer and direct hydrogenation of prochiral ketones and alkenes at moderate temperatures but without any discernible enantioselectivity.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Cardiff Catalysis Institute (CCI) Chemistry
Subjects:	Q Science > QD Chemistry
Publisher:	RSC
ISSN:	1477-9226
Last Modified:	18 Oct 2022 12:24
URI:	https://orca.cardiff.ac.uk/id/eprint/9705

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