FURTHER X-RAY AND NMR INVESTIGATIONS ON BIS-TRIPHENYLPHOSPHINO-PLATINUM COMPLEXES WITH POLYSUBSTITUTED OLEFINS

Phosphine C-13 and P-31 NMR spectra are discussed for the compounds Pt(PPh3)2(eta-2-olefin), with olefin = CH(CN) = CH2, trans-CH(CN) = CH(CN), C(CN)2 = CH(CN), C(CN)2 = C(CN)2, CH(COOCH3) = CH2, trans-CH(COOOCH3) = CH(COOOCH3), C(COOOCH3)2 = CH(COOOCH3), C(COOOCH3)2 = C(COOOCH3)2, C(CN)2 = C(CH3)2. The chemical shifts of the phosphine para carbons reveal that CN or COOCH3 groups bound to the olefin extend their electron-withdrawing effects as far as these carbons. The Pt-195 NMR spectrum of the last compound and the P-31 NMR spectrum of Pt(PPh3)2[C(CN)2 = CH(OCH3)] are also reported. For Pt(PPh3)2[C(COOOCH3)2 = CH(COOOCH3)] the solid state structure, as determined by X-ray diffraction methods, is described. Cell parameters are: a = 14.275(5), b = 14.464(4), c = 12.172(4) angstrom, alpha = 84.29(2), beta = 81.44(2), gamma = 63.86(2)-degrees, space group P1BAR. Substituents bending back occurs and conjugation results allowed only for the two trans carbonyls. A structural analysis is made for all of the title compounds so far studied by diffraction methods. This indicates that the P-Pt-P bond angle and the dihedral angle between the P-Pt-P and C-Pt-C planes are governed by intramolecular contacts between the olefin substituents and the phosphine ligands. For acyclic olefins, the P-Pt-P bond angle increases in the order CX2 = CX2 < CX2 = CY2 <trans-CHX = CHX < CH2 = CH2.