C-13 ipso chemical shifts in the aryl phosphino-thioether complexes PdX(p-RC6H4(P,S). On resonance effects into the aryl ring

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-tet ra-O-acetyl-1-{(2-diphenylphosphino)benzylthio}-beta-D-glucopyranose){(2-Ph 2PC6H4CH2)-SCHCH(OAc)CH(OAc)CH(oAc)CH(CH2OAc)O}). Their C-13 NMR spectra sh ow that (i) the aryl ipso carbon, Cl, with delta=136.3-167.4, is always shi fted to higher frequencies relative to both the model organic compound H-C6 H4-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 c orrelation coefficient = 0.985. (iii) pi-Bonding from the Pd(II) to the ary l is suggested to be of secondary importance. (C) 1999 Elsevier Science S.A . All rights reserved.