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Elsevier, Journal of Organometallic Chemistry, (545-546), p. 131-137

DOI: 10.1016/s0022-328x(97)00232-5

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Steric and electronic effects on E/Z composition of exocyclic cyclopalladated N-benzylideneamines

Journal article published in 1997 by Joan Albert, Jaume Granell ORCID, Anna Luque, Mercè Font-Bardía, Xavier Solans
This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Abstract

Exocyclic six-membered cyclopalladated dimers 2a-2c, , have been prepared by reaction of palladium(II) acetate with N-benzylidene-2-phenylanilines 1a-1c, RCH=NC6H4-2-C6H5 {1a, R = 2,6-Cl2C6H3; 1b, R = 2,6-F2C6H3 and 1c, R = 2,4,6-(CH3O)3C6H2}, and a subsequent metathesis reaction with LiBr. Reaction of 2 with PPh3 produced mononuclear compounds 3, . Analysis of the 1H NMR methinic region of 2 and 3 revealed their E/Z composition. 2a and 2b present imines in E and Z configuration in an approximate ratio of 1:1, white 2c consists almost exclusively of imines in E configuration. Compounds 3 also present imines in E and Z configuration, the former are more abundant in all cases (≥ 4:1). The crystal structure of 3c with the imine in E configuration has been determined. It crystallizes in the monoclinic space group P21/a with a = 19,258(3) Å, b = 13.177(2) Å, c = 14.660(2) Å and β = 113.78(2)°. Steric and electronic effects on the E/Z composition of 2 and 3 and related exocyclic cyclopalladated N-benzylidenebenzylamines suggest that, for compounds of this type, the E → Z isomerization takes place via a rotation through the N=C bond which is assisted by π back bonding of the palladium(II) center to the iminic function.