AROMATIC LEAD(IV) COMPOUNDS PART XV - SYNTHESIS AND MULTINUCLEAR NMR PROPERTIES OF COMPOUNDS OF THE (C6H5)(3)PBR (R = ALKYL, ALKENYL, ALKYNYL)

The synthesis and multinuclear NMR properties of compounds of the type (C6H5)(3)PbR (R=alkyl, alkenyl, alkynyl) are reported. Introduction o f a C=C or a C=C bond next to the lead atom leads to a high field shif t of the lead chemical shift of ca. 60 ppm to 130 ppm, respectively, w hile there is also a distinct influence on the values of the lead-prot on and lead-carbon coupling constants. This so called neighboring bond effect is discussed on the basis of the Fermi contact interaction. Se veral approaches to this interaction have been discussed referring to the present data and those published earlier. The spin density at the nucleus depends on the overlap integral, the ionicity of the bond or f raction of charge transferred, the s orbital participation and the p c haracter of the bonding orbital.