INFLUENCE OF THE LENGTH OF THE QUATERNIZATION GROUP ON THE CYCLOMETALATION OF [M(2,4'-R-BIPY)CL3] (M=PT(II) OR PD(II), 2,4'-R-BIPY=1'-ALKYL-2,4'-BIPYRIDINIUM)

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 o r C10H21) gave the cyclometallated complexes [M(2,4'-R-bipy - H)Cl2] i n quantitative yield. For M = Pd there is no clear variation of the cy clometallation 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 aqueou s solution depends on the solubility of the complex and decreases as t he hydrophobicity of the chain increases.