Fluxional characteristics of palladium(II) halide complexes of cyclic selenoethers. A dynamic nuclear magnetic resonance study
- 1 January 1986
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 1,p. 205-211
- https://doi.org/10.1039/dt9860000205
Abstract
The series of complexes [PdX2{[graphic omitted]H2)n}2s](n= 4–6; X = Cl, Br, or I) and [PdX2{S[graphic omitted]H2}2](X = Cl, Br, or I) have been synthesised and their stereodynamics investigated by variable- temperature 1H n.m.r. spectroscopy. Whereas conformational changes of the various sized ligand rings were always fast on the n.m.r. chemical shift time- scale, the rates of inversion of the co- ordinated selenium atoms were much slower and directly measurable by bandshape fitting methods. ΔG‡ values for selenium inversion were in the range 66–78 kJ mol–1. Values were observed to increase consistently with decreasing ligand ring size and are explained in terms of the extents of angle strain required to achieve the transition- state structure of the inversion process. The inversion energies of all four series of complexes reflect a cis halogen influence of 5.1–7.3 kJ mol–1.Keywords
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