UC Riverside

Heterogeneous catalysts are widely used in industry. Common methods of synthesizing heterogeneous catalysts can lead to distributions of metal coordination environments making it challenging to apply structure–property relationships common in homogeneous chemistry. Surface organometallic chemistry (SOMC) combines the advantages of homogeneous and heterogeneous catalysis fields to develop well-defined heterogeneous catalysts that allow for structure-property optimization. The most common method to generate catalytic active sites in SOMC is to react an organometallic with a high surface area oxide. The speciation of MOx sites on high surface area metal oxides depends on the Brønsted acidity of surface OH sites. For example, supporting an organometallic on SiO2 results in the formation of MOx sites while supporting an organometallic on sulfated zirconium oxide (SZO) results in the formation of [M][Ox] electrostatic ion-pairs. The first part of this thesis examines the acidity of SZO dehydroxylated at 300°C (SZO300) through the generation of [R3PH][SZO] ion pairs. [R3PH][SZO] can further react with bis(cyclooctadiene)nickel ([Ni(cod)2]) to form [Ni(PAr3)(codH)][SZO300] which are active for the polymerization of ethylene. A part of this thesis presents the synthesis of [Ir(cod)py][SZO300] via two complementary synthetic methods. [Ir(cod)py][SZO300] is active for the dearomative borylation of pyridines. The characterization and reactivity of these ion pairs will be discussed. The next part of this thesis focuses on developing a well-defined Schrock alkylidene on SZO. W=O(Adene)(2,5-Me2pyr)2 reacts with SZO to form [W=O(Adene)(2,5-Me2pyr)][SZO300], and has activity for the metathesis of terminal olefins with high E selectivity. This is the first example of a supported W-oxo alkylidene on a sulfated oxide. The final part of this thesis studies at the reaction of W(C4H8)(NAr)(OSiPh3)2 (NAr = 2,6-iPr2C6H3) with partially dehydroxylated silica to form (≡SiO)(W(NAr)(C4H8)(OSiPh3). This supported metallacyclopentane undergoes thermal ring contraction to form (≡SiO)(W(NAr)(C3H8Me)(OSiPh3). This reaction also occurs in the presence of blue LEDs (λ = 450nm). This reaction establishes a route to access active olefin metathesis intermediates without generating an alkylidene. (≡SiO)(W(NAr)(C4H8)(OSiPh3) is active for the direct conversion of ethylene to propylene.