Syntheses of Lipophilic Werner Complexes For Application as Chiral Hydrogen Bond Donors in Enantioselective Catalysis and Investigation of the Effect of Chloride on Fluid Catalytic Cracking Catalysts

Abstract

Swiss chemist and 1913 Nobel laureate Alfred Werner is commonly referred to as the father of coordination chemistry. Wener synthesized a myriad of inorganic complexes and accurately predicted the bonding relationships between the metals, ligands, and anions. Werner was tremendously influential on the development of inorganic chemistry. In opposition to the theories of many of his contemporaries, Werner insisted chirality could exist at the metal center of certain coordination compounds. Demonstrating this point, Werner successfully resolved the enantiomers of [Co(en)3]3+ (en = 1,2-ethylenediamine) into their respective Λ and Δ forms via fractional crystallization from diastereomeric tartrate salts. Analysis of crystal structures of tris(ethylenediamine) complexes reveals that the NH units of the ligands exhibit a propensity to function as exceptional hydrogen bond donors to counter anions. The century long dormancy of the use of these compounds in synthetic applications can be attributed to their meager organic solublity and low spin d6 electron configuration, rendering these octahedral complexes kinetically substitution inert. Thankfully, anion methathesis with lipophilic counteranions unlocks substantial organic solubility, relieving competition between substrates and anions for NH active sites. The mechanism of hydrogen bond donating organocatalysts is not entirely understood. However, modifications to the ligands, anions, and metals has provided insight into catalytic enantioselectivity and kinetics. In an unrelated project, nickel, a common contaminant in crude oil, deposits on Fluid Catalytic Cracking (FCC) catalysts and induces unwanted dehydrogenation reactions. These lead to an increase in hydrogen and coke, inhibiting the FCC unit from reaching its optimal operation. In this study, equilibrium catalyst samples obtained from industrial FCC units are exposed to chloride ions, and changes in physicochemical characteristics, catalytic selectivity, and the reducibility of nickel are analyzed. Spectroscopic analyses show that the interaction with chloride ions alters the electronic environment of nickel and Advanced Cracking Evaluation studies show equilibrium catalysts that were exposed to chloride ions gave higher coke and H2 yields. These results bridge the gap between existing literature and the FCC environment by demonstrating that chloride ions can interact and reactivate nickel contaminant on FCC catalysts.