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Synthesis, structure and dynamics of NHC-based palladium macrocycles
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Andrew, Rhiann and Chaplin, Adrian B. (2014) Synthesis, structure and dynamics of NHC-based palladium macrocycles. Dalton Transactions, Volume 43 (Number). pp. 1413-1423. doi:10.1039/c3dt52578c ISSN 1477-9226.
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Official URL: http://dx.doi.org/10.1039/C3DT52578C
Abstract
A series of macrocyclic CNC pincer pro-ligands based on bis(imidazolium)lutidine salts with octa-, deca- and dodecamethylene spacers have been prepared and their coordination chemistry investigated. Using a Ag2O based transmetallation strategy, cationic palladium(II) chloride complexes [PdCl{CNC–(CH2)n}][BArF4] (n = 8, 10, 12; ArF = 3,5-C6H3(CF3)2) were prepared and fully characterised in solution, by NMR spectroscopy and ESI-MS, and in the solid-state, by X-ray crystallography. The smaller macrocyclic complexes (n = 8 and 10) exhibit dynamic behaviour in solution, involving ring flipping of the alkyl spacer across the Pd–Cl bond, which was interrogated by variable temperature NMR spectroscopy. In the solid-state, distorted coordination geometries are observed with the spacer skewed to one side of the Pd–Cl bond. In contrast, a static C2 symmetric structure is observed for the dodecamethylene based macrocycle. For comparison, palladium(II) fluoride analogues [PdF{CNC–(CH2)n}][BArF4] (n = 8, 10, 12) were also prepared and their solution and solid-state structures contrasted with those of the chlorides. Notably, these complexes exhibit very low frequency 19F chemical shifts (ca. −400 ppm) and the presence of C–HF interactions (2hJFC coupling observed by 13C NMR spectroscopy). The dynamic behaviour of the fluoride complexes is largely consistent with the smaller ancillary ligand; [PdF{CNC–(CH2)8}][BArF4] exceptionally shows C2v time averaged symmetry in solution at room temperature (CD2Cl2, 500 MHz) as a consequence of dual fluxional processes of the pincer backbone and alkyl spacer.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QD Chemistry | ||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | ||||
Library of Congress Subject Headings (LCSH): | Nuclear magnetic resonance spectroscopy, Ligands (Biochemistry), Macrocyclic compounds | ||||
Journal or Publication Title: | Dalton Transactions | ||||
Publisher: | Royal Society of Chemistry | ||||
ISSN: | 1477-9226 | ||||
Official Date: | 2014 | ||||
Dates: |
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Volume: | Volume 43 | ||||
Number: | Number | ||||
Page Range: | pp. 1413-1423 | ||||
DOI: | 10.1039/c3dt52578c | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Open Access (Creative Commons) | ||||
Date of first compliant deposit: | 26 December 2015 | ||||
Date of first compliant Open Access: | 26 December 2015 | ||||
Funder: | University of Warwick, Royal Society (Great Britain) |
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