Issue 12, 2018

Synthesis, structural characterization and NMR studies of group 10 metal complexes with macrocyclic amine N-heterocyclic carbene ligands

Abstract

A series of Ni(II), Pd(II) and Pt(II) complexes [ML][PF6]2 [L = L1, M = Ni (1), Pd (2), Pt (3); L = L2, M = Ni (4), Pd (5), Pt (6)] and [Pt(L2)(acac)] (7) have been prepared by the reactions of two tetradentate macrocyclic amine-NHC ligand precursors, [H2L1][PF6]2 and [H2L2][PF6]2, with Ni(OAc)2·4H2O, Pd(OAc)2 and Pt(acac)2 in the presence of NaOAc. Complex 7 is isolated along with 6 from the same reaction between [H2L2][PF6]2 and Pt(acac)2. There are two atropisomers in 1–3 and two achiral conformers in 4–6. The crystal structures of 1–3 and one conformer of 4–6 (4a–6a) have been determined by single-crystal X-ray diffraction studies. The metal ion is found to reside in the cavity of the macrocyclic ring and adopts a square-planar configuration. Detailed NMR studies including variable-temperature NMR spectroscopy reveal a dynamic interconverting process between two atropisomers of 1–3 in the solutions via a ring twisting mechanism. Two conformers in the equilibrated solution of 4–6, probably arising from the orientation of two amine N–H bonds with respect to the coordination plane, exchange slowly. Time-dependent 1H NMR spectra show that one conformer (4a–6a) in solution converts into the other (4b–6b) via the inversion of the nitrogen atom.

Graphical abstract: Synthesis, structural characterization and NMR studies of group 10 metal complexes with macrocyclic amine N-heterocyclic carbene ligands

Supplementary files

Article information

Article type
Paper
Submitted
10 Dec 2017
Accepted
02 Feb 2018
First published
06 Feb 2018

Dalton Trans., 2018,47, 4282-4292

Synthesis, structural characterization and NMR studies of group 10 metal complexes with macrocyclic amine N-heterocyclic carbene ligands

T. Lu, Z. Liu, C. A. Steren, F. Fei, T. M. Cook, X. Chen and Z. Xue, Dalton Trans., 2018, 47, 4282 DOI: 10.1039/C7DT04666A

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