Further x-ray and NMR investigations on bis-triphenylphosphino-platinum complexes with polysubstituted olefins

Abstract

Phosphine 13C and 31P NMR spectra are discussed for the compounds Pt(PPh 3) 2(η 2-olefin), with olefin  CH(CN) CH 2, trans-CH(CN)CH(CN), C(CN) 2=CH(CN), C(CN) 2 C(CN) 2, CH(COOCH 3)CH 2, trans-CH(COOCH 3)CH(COOCH 3), C(COOCH 3) 2CH(COOCH 3), C(COOCH 3) 2C(COOCH 3) 2, C(CN) 2C(CH 3) 2. The chemical shifts of the phosphine para carbons reveal that CN or COOCH 3 groups bound to the olefin extend their electron-withdrawing effects as far as these carbons. The 195Pt NMR spectrum of the last compound and the 31P NMR spectrum of Pt(PPh 3) 2[C(CN) 2CH(OCH 3)] are also reported. For Pt(PPh 3) 2[C(COOCH 3) 2CH(COOCH 3)] 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) Å, α=84.29(2), β=81.44(2), γ=63.86(2)°, space group P 1 . 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 CX 2CX 2‘CX 2CY 2< trans- CHXCHX < CH 2CH 2.