Influence of the length of the quaternisation group on the cyclometallation of [M(2,4′-R-bipy)Cl3](M = PtII or PdII; 2,4′-R-bipy = 1′-alkyl-2,4′-bipyridinium)

Abstract

Solid-state thermolysis of the 1′-alkyl-2,4′-bipyridinium complexes [M(2,4′-R-bipy)Cl₃](M = Pd^II or Pt^II; R = H, Me, Bu, C₆H₁₃, C₈H₁₇ or C₁₀H₂₁) gave the cyclometallated complexes [M(2,4′-R-bipy – H)Cl₂] in quantitative yield. For M = Pd there is no clear variation of the cyclometallation temperature with the length of the alkyl chain, whereas the temperature of cycloplatination decreases steadily as the length of the alkyl chain increases. The extent of cyclometallation in aqueous solution depends on the solubility of the complex and decreases as the hydrophobicity of the chain increases.