Issue 39, 2019

Cyclotriveratrylene-tethered trinuclear palladium(ii)–NHC complexes; reversal of site selectivity in Suzuki–Miyaura reactions

Abstract

The trinuclear complexes [{PdI2(pyCl)}3(L1)] C1 and [{PdI2(pyCl)}3(L2)] C2, where pyCl = 3-chloropyridine, L1 = methyl(cyclotriguaiacylenyl)methylbenzimidazol-2-ylidene and L2 = benzyl(cyclotriguaiacylenyl)methylbenzimidazol-2-ylidene, each feature three palladium N-heterocyclic carbene (NHC) centres tethered onto a host-type cyclotriguaiacylene scaffold. Crystal structures of different solvates of complex C1 reveal different host–guest motifs including intra-cavity binding of dioxane guests concomitant with intramolecular halogen bonding interactions of C1. Mononuclear NHC analogues of C1 and C2, namely [PdI2(pyCl)(L3)] C3 and [PdI2(pyCl)(L4)] C4, where L3 = (3-chloropyridyl)-1-(2-methoxyphenyoxy)methyl-3-methylbenzimidazol-2-ylidene and L4 = (3-chloropyridyl)-1-(2-methoxyphenyoxy)methyl-3-benzylbenzimidazol-2-ylidene, were also synthesised and their crystal structures determined. Complexes C1–C4 are competent catalysts for Suzuki Miyaura cross-coupling, and interestingly exhibit a switch in the normal regioselectivity observed for reactions of 2,4-dibromopyridine with aryl boronic acids, usually C2-selective, yielding C4-arylated product preferentially over C2-arylated product.

Graphical abstract: Cyclotriveratrylene-tethered trinuclear palladium(ii)–NHC complexes; reversal of site selectivity in Suzuki–Miyaura reactions

Supplementary files

Article information

Article type
Paper
Submitted
20 Aug 2019
Accepted
14 Sep 2019
First published
20 Sep 2019

Dalton Trans., 2019,48, 14687-14695

Cyclotriveratrylene-tethered trinuclear palladium(II)–NHC complexes; reversal of site selectivity in Suzuki–Miyaura reactions

J. M. Fowler, E. Britton, C. M. Pask, C. E. Willans and M. J. Hardie, Dalton Trans., 2019, 48, 14687 DOI: 10.1039/C9DT03400E

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