13C ipso chemical shifts in the aryl phosphino-thioether complexes PdX(p-RC6H4)(P,S). On resonance effects into the aryl ring
作者:M Tschoerner、P.S Pregosin
DOI:10.1016/s0020-1693(99)00120-6
日期:1999.6
The complexes PdX(p-RC6H4)(P,S) (2), have been prepared (X = Br I; R = OMe, Me, H, CO2Me, CF3, NO2; P S = the phosphine-thioether-chelate (2,3,4,6-tetra-O-acetyl-1-(2-diphenylphosphino)benzylthio}-beta-D-glucopyranose)(2-Ph2PC6H4CH2)-SCHCH(OAc)CH(OAc)CH(oAc)CH(CH2OAc)O}). Their C-13 NMR spectra show that (i) the aryl ipso carbon, Cl, with delta=136.3-167.4, is always shifted to higher frequencies relative to both the model organic compound H-C6H4-R, and the diamine complexes PdI(p-RC6H4)(TMEDA). (ii) There is a linear correlation between delta Cl and the Hammett constant sigma(p+) with the correlation coefficient = 0.985. (iii) pi-Bonding from the Pd(II) to the aryl is suggested to be of secondary importance. (C) 1999 Elsevier Science S.A. All rights reserved.