Crystal structures of three para-substituted-styryl(pyridyl)platinum(II) complexes; effect of substituent on molecular geometry

Abstract

X-Ray crystal-structure analysis has been carried out on three square-planar para-substituted-styryl(pyridyl)platinum(II) complexes [(p-YC₆H₄CH:CH₂)PtCl₂(NC₂H₄X)] where (I) Y = NMe₂. X = Me: (II) Y = H, X = Me; and (III) Y = NO₂, X = Cl. The distances of the platinum atom from the two ethylenic carbon atoms are well correlated with the n.m.r. ¹⁹⁵Pt–¹³C coupling constants when both are plotted vs. σ_p⁺, a measure of electron-donating power of the substituent Y. Both this, and the deviation of the co-ordination plane from the ethylenic bond, can be given a simple valence-bond explanation.