Zirconium complexes of two different iminopyrrolyl ligands - Syntheses and structures

The reaction involving N-aryliminopyrrolyl ligand, 2-((p-Me-C 6H3N=CMe)-C4H3NH) (1a) (Imp Me-H), and Zr(OtBu)4 in a 2:1 molar ratio in toluene at 90 °C afforded the corresponding bis(iminopyrrolyl) complex of zirconium, [(ImpMe)2Zr(OtBu)2] (2a) having two bidentate iminopyrrole groups in the coordination sphere. In contrast, the bulkier 2-((2,6-iPr2C6H3N=CH)-C4H 3NH) (1b) (ImpDipp-H) and Zr(OtBu)4 in a 1:1 molar ratio under the same condition yielded the corresponding mono(iminopyrrolyl) complex of zirconium, [(ImpDipp)Zr(OtBu) 3(THF)] (2b), which contains only one bidentate iminopyrrole moiety in the coordination sphere. Both complexes were characterized by single-crystal X-ray diffraction analysis. The solid-state structures reveal that the bulky iminopyrrole ligands cause a steric crowding around the zirconium ion along with three tert-butoxide ligands attached to the central metal ato