The preparation of beta-diketiminato organochromium complexes for homogeneous olefin polymerization catalysis

This dissertation describes research on paramagnetic beta-diketiminato chromium complexes, and in particular, the synthesis and olefin polymerization reactivity of cationic CrIII alkyl complexes as homogeneous models for the Phillips catalyst, i.e. CrO3/SiO2.; Chapter 1 discusses the synthesis and reactivity of the cationic chromium alkyl complex [(2,6-Me2Ph)2nacnacCr(OEt2)CH 2SiMe3]+ BARF- (39). Catalyst 39 is a homogeneous model for the Phillips olefin polymerization catalyst.; In Chapter 2, we have investigated the synthesis of CrII alkyl complexes as precursors to three coordinate chromium alkyl polymerization catalysts. The attempted alkylation of [(2,6-iPr2Ph) 2nacnacCr(mu-Cl)]2 (36) with allyl magnesium chloride gave an allyl complex, i.e. (2,6-iPr2Ph) 2nacnacCr(eta3-Allyl) (57). The pyridine derivative [(2,6-iPr2Ph)2nacnacCr(py)Cl] (59) was synthesized in an effort to discover an efficient route to the proposed three-coordinate "base free" polymerization catalyst [(2,6- iPr2Ph)2nacnacCr (CH2Si(CH3 )3)]+ BARF- (54). The transformation to 59 was achieved via treatment of 36 with two equivalents of pyridine.; Chapter 3 reports the synthesis of a novel class of nacnac chromium "internal base alkyl" (IBA) complexes. Lithium-hydrogen exchange reactions between tert-butyl lithium and the corresponding alkoxytrimethylsilane provided the IBA precursors (EtO)(CH3)2SiCH2Li (75) and (tBuO)(CH3)2SiCH2Li ( 77). The reaction of 37 with two equivalents of IBA anion 77 yielded the IBA complex (2,6-Me2Ph)2nacnacCr(CH 2Si(OtBu)(CH3)2) 2 (86). Attempted protolysis of 86 with one equivalent of H(Et2O)2BARF did not yield a stable cationic chromium IBA complex, i.e. [(2,6-Me2Ph)2nacnacCr(CH 2Si(OtBu)(CH3)2)]+ BARF (87). (Abstract shortened by UMI.)...