Transition metal complexes supported by pyrrolide and imidazoline ligands with pyridine donors

Abstract

Meridonal proligands featuring central pyrrolide and imidazoline moieties flanked by two pyridine donors with arene substituents ortho to N have been synthesized and their coordination chem. complexes of di-, tri-, and tetravalent transition metals explored. These ligands show variable coordination modes as a function of metal and redox state. Yttrium complexes of the dipyridyl pyrrolide (DPP) ligand show tridentate binding in the solid state and π-stacking with substituents such as indolide. The DPP Y dialkyl complex promotes C-H activation of the Me group of 2,6-lutidine resulting in C-C bond formation with pendant arene substituents. The DPP-supported tris(dimethylamido) Ti complex shows dissocn. of one pyridine donor in the solid state. In the presence of alkyl aluminum reagents, DPP Ti and Zr dimethylamido complexes act as catalysts for the polymn. of ethylene. Bisligated six-coordinate Fe(II) complexes supported by two DPP ligands or two dipyridyl imidazoline (DPC) ligands show π-stacking interactions between the ligand backbone and arene substituents. Redn. of the [Fe(DPC)_2]^(2+) complex by two electrons affords a neutral fourcoordinate complex resulting from dissocn. of two pyridine arms.