An investigation of carbonyl insertion into M-CF3 bonds

Jacob, Jayanthi (1990) An investigation of carbonyl insertion into M-CF3 bonds. Masters thesis, Memorial University of Newfoundland.

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Abstract

Carbonyl insertion continues to be of current interest as it plays a vital role in many industrial preparations like hydroformylation, Reppe synthesis, Fischer-Tropsch process, etc. Carbonyl insertion has not been observed in M-CF₃ bonds (M = transition metals) and the first report of apparent carbonyl insertion in a Fe-CF₃ bond stands in open conflict with both experimental and theoretical results. An investigation of the above report is presented in this thesis. -- Fe(CO)₃(diars) (diars = o-phenylenebis(dimethylarsine)) reacts with excess CF₃)I to form the perfluoroacyl Fe(CO)₂(diars)(C(O)CF₃)I and the per-fluoroalkyl Fe(CO)₂(diars)(CF₃)I compounds in varying yields, depending on the reaction conditions. A high concentration ratio of CF₃I to Fe(CO)₃(diars) favours the perfluoroalkyl while a dilute solution favours the perfluoroacyl compound. Concentration vs. time profiles of the reaction monitored by ¹⁹F NMR, indicate that the perfluoroalkyl and perfluoroacyl compounds are formed by two independent reaction pathways. The perfluoroalkyl is formed by oxidative addition of CF₃I to Fe(CO)₃(diars) by a nonchain, free radical mechanism while the perfluoroacyl is formed by an intermolecular insertion mechanism via an ionic intermediate. The higher analogues of CF₃I form only the perfluoroalkyl owing to the greater stability of the Rf radical which enhances the rate of the free radical reaction. -- Two isomers of the perfluoroalkyl compound were isolated and spectroscopically identified by ¹H, ¹³C, ¹⁹F NMR, IR and Mass spectra as cis,cis and cis,trans isomers. Similarly, four isomers of the perfluoroacyl compound were isolated and identified. The structures of one perfluoroacyl and one perfluoromethyl isomer were confirmed by single crystal X-ray data.

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