Epoxidation and bleaching catalyses by homo- and heterogeneous manganese, cobalt, and iron azamacrocyclic complexes
Abstract
Using H2O2 as oxidant the complex, Fe(L)(CH3CN)2•2PF6− is capable of catalyzing the epoxidation of small olefins, with preference for electron rich substrates, on the order of 50–70 turnovers, with greater than 95% selectivity toward epoxide. The Ci monoclinic complex was synthesized by reaction of the cyclam-derived ligand with in situ iron triflate in acetonitrile, and characterized by microanalysis, mass spectrometry, and X-ray crystallography. A complete mechanism which invokes FeIII-O-O-H as the active species in a catalytic cycle that competes fiercely with oxidative decomposition has been previously proposed. A solvent and temperature study was conducted on homo- and heterogeneous MnTMTACN, in order to optimize catalytic conditions. It was found that a 1:1 metal:ligand ratio, low temperature, and acetone solvent gave an optimum conversion of 1000 turnovers in 24 hours, after which side products begin to appear. Introducing ligand into the silica cage molecule Zeolite Y via hexane solvent impregnation produced a slightly active catalyst with low conversion. Azamacrocyclic manganese and cobalt catalysts encapsulated in zeolite Y were tested for bleach activation in the decoloration of Morin dye. The catalysts activate bleach at 20°, much lower than the temperatures currently necessary for standard formulas. Catalytic activity proceeds seemingly uninfluenced by zeolite crystal size or choice of ligand. Cobalt is the more active of the two metals, effecting a 93% decoloration of Morin in less than five minutes. Niobium chloroaryloxides react with lithium silane agents to yield a mixture of chloro-, tris-alkyl, and alkylidene complexes, characterized by 29Si NMR. Similar complexes react with pyridine and phosphine to create adducts whose structures are distorted away from strict octahedral symmetry.
Degree
Ph.D.
Advisors
Rothwell, Purdue University.
Subject Area
Chemistry
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.