Vanadium phosphinimide complexes for ethylene polymerization and the chemistry of phosphinimines and phosphine oxides with borane reagents.
Date of Award
Chemistry and Biochemistry
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A reproducible and high yielding synthesis of the vanadium imide phosphinimide complexes of the general formula V(NAr)(NPR3)Cl2 (Ar = Ph, C6H3-2,6-i-Pr2; R = i-Pr, t-Bu, Ph) has been developed. These complexes upon activation by methylaluminoxane demonstrated low to moderate ethylene polymerization activities comparable to published vanadium imide complexes. The dichloride derivatives react readily with a variety of alkali metal salts and Grignard reagents to produce vanadium imide phosphinimide thiolate, alkyl, aryl, amide and alkoxide complexes. In the presence of Zn, reduction of V(NPh)(NPt-Bu3)Cl2 occurred to afford what is proposed to be a vanadium(IV) imide bridged dimeric species (V(mu-NPh)(NPt-Bu3)Cl)2. The reaction of pinacolborane with phosphinimines (HNPR3) proceeds via two observable reaction pathways: a metathesis reaction, in which hydrogen gas is evolved, or the reduction of phosphorus, in which the corresponding borylamine and tertiary phosphine are formed. Experimental results and a DFT study showed that the preferred mechanism is dictated by the steric bulk of the R groups. The analogous reductions of phosphine oxides with pinacolborane gave tertiary phosphines and O(Bpin)2. Alternative synthetic procedures and subsequent reactions of O(Bpin)2 with both metal and main group complexes were investigated. These reactions led to the synthesis of Zr(C 5H5)2(OBpin)2, [t-Bu 3PNH2][pinB(OBpin)2], and degradation products. N-borylphosphinimines of the general formula (R 3Pmu-NBcat)x (cat = O2C6H4; R = Et, n-Bu, i-Pr, Ph, t-Bu; R3 = n-Bu(t-Bu)2; x = 1,2) were synthesized. The dimeric or monomeric nature of the above compounds were probed by X-ray and NMR methods, revealing that the steric bulk of the R groups affected the preferred bonding mode of the complexes in solution and in solid state. Therefore, metathesis reactions have led to the synthesis of both vanadium phosphinimide complexes and N-borylphosphinimine complexes. It has been determined that the steric bulk of the substituents of the phosphinimine affect the bonding mode of the N-borylphosphinimine complexes and their reactivity with boranes.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .H39. Source: Dissertation Abstracts International, Volume: 66-11, Section: B, page: 5974. Thesis (Ph.D.)--University of Windsor (Canada), 2005.
Hawkeswood, Sarah Bess., "Vanadium phosphinimide complexes for ethylene polymerization and the chemistry of phosphinimines and phosphine oxides with borane reagents." (2005). Electronic Theses and Dissertations. 4500.