Transition metal complexes of monodentate 2-oxazolines containing long chain alkyl groups. The crystal structure of trans-PdCl2(κ 1-N-rac-2-heptadecyl-4,5-dihydro-5-methyl-2-oxazole)2

Abstract

Abstract The synthesis, characterisation and properties of several divalent metal complexes (Co, Ni, Pd) containing 2-oxazoline ligands L1–L3, appended with long chain alkyl and/or ester groups, is reported. The X-ray crystal structure aspects of one such complex, trans-PdCl2(rac-2-heptadecyl-4,5-dihydro-5-methyl-2-oxazole)2 (i.e. PdCl2(L1)2: 3), is described. This latter material contains one of the longest alkyl chains to be crystallographically characterised appended to an oxazoline ligand. The complexes reported herein represent the first transition metal derivatives of these high molecular weight, long chain and presumably low polarity monodentate oxazoline ligands. A combination of spectral and theoretical calculations (semi-empirical PM6(tm) level of theory) are used to support the proposed structure in the case of the hydrates of NiCl2 and CoBr2 complexes derived from L1. A trio of PdCl2 complexes of the ligand set are likewise detailed. Complex 3 is shown to be a useful pre-catalyst for the promotion of a Heck coupling reaction between bromobenzene and styrene under typical conditions.