Damien Reardon - Vanadium-Promoted Aldol Condensation and Pinacolic Coupling of Acetylpyrrole:  Formation of Two New Potent Dinuclear Catalysts for Olefin Copolymerization

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  Reardon, Damien, Guan, Jingwen, Gambarotta, Sandro, Yap, Glenn P.   A., Wilson, David R. Organometallics  2002 21 (21) 4390-4397

  Abstract: Reaction of VCl3(THF)3 with 3 equiv of   the potassium salt of acetylpyrrole, K[α-(CH3CO)C4H3N], afforded   the dinuclear   {V2[K(THF)]2[CH3CO(C4H3N)]2}[(C4H3N)C(O)CH2C(C4H3N)(CH3)O]2 (1),   where four acetylpyrrolide anions from two vanadium moieties have   undergone an aldol condensation. The two pyrrolyl?acetylacetonate   units so generated work as tetradentate binucleating ligands   holding together the dinuclear structure. A similar reaction   carried out on the divalent [V2Cl3(THF)6]2[Zn2Cl6] salt afforded   the dinuclear and trivalent   {VK(THF)[(C4H3N)C(O)CH3]}2[(C4H3N)(CH3)(O)CC(O)(CH3)(C4H3N)]·0.5(toluene)   (2), where two acetylpyrrolide ligands, one per vanadium atom,   have undergone a reductive coupling to form a pinacol. Even in   this case the dipyrrolylpinacol works as a tetradentate   binucleating ligand holding together the dinuclear frame.   Attempts to perform the same reaction on another V(II) salt such   as VCl2(TMEDA)2 (TMEDA = N,N,N?,N?-tetramethylethylenediamine)   afforded instead the corresponding divalent derivative   V(TMEDA)[(C4H3N)C(O)CH3]2 (3), where the acetylpyrrolide anions   remained intact. Both 1 and 2 are potent olefin copolymerization   catalysts upon activation with diethyl aluminum chloride, while 3   displays low but not negligible activity.

  Address (URL): http://dx.doi.org/10.1021/om0204585