Reports: ND351756-ND3: Catalytic Carbonylation of Ketenes under Oscillating Pressures of Carbon Monoxide

Carl D. Hoff, PhD, University of Miami

The goal of this proposal is to investigate the possibility of utilizing variation in CO pressure as a tool to enhance catalytic carbonylation of diazocompounds to ketenes as well as to investigate new catalytic systems for that reaction. Progress in both reactor design and chemical reactions have been made during the last year.

The investigation of mixed metal catalysis by [Co(CO)4]2 and [Cp(CO)3Cr]2has been investigated under both CO and Ar gas pressure. It appears to show properties superior to either metal alone. Detailed kinetic investigation of this system is in progress. The reaction of [Cp*(CO)3Cr]2 with (Me3Si)(H)C=N=N has also been studied under variable and oscillating pressures of Ar and CO. The goal is initiation under Ar of rapid binding of the diazo compound and its conversion to a bound ketene product and then liberation of that product by CO addition. This is then repeated in a second cycle and interception of the intermediate organometallic product Cp*2(CO)5Cr2at this stage of the reaction has been shown to help prevent its decomposition. Using a simplified reactor we have been able to extend the stoichiometric conversion to a catalytic one with about five additional turnovers for oscillatory versus normal conditions.

Improvements in design of the prototype low pressure glass reaction system for studying reactions under oscillating CO pressure are in progress in collaboration with Professor Hongtan Liu in the Chemical Engineering department at the University of Miami. This is currently being redesigned and an all metal system capable of higher pressures and more rapid gas/liquid equilibration is being built. This system will also be coupled to an FTIR Microscope cell to allow flow through monitoring of reaction conditions. This will allow smaller samples to be used in kinetic measurements and also allow more rapid measurments.

In addition to carbonylation of diazo compounds to ketenes, we have begun inivestigation of other carbonylation and oxidation reactions for which an oscillating gas pressure may be beneficial. In particular, the reductive carbonylation of PhNO to PhNCO and CO2 by N-hetrerocylic carbene containing late transiton metal complexes has been explored as a potential area for development of catalytic carbonylation. In terms of catalytic oxidation under oscillating pressure conditions, the reactivity of N2O with both early and late transiton metal complexes has been explored in the first year.

Redesign work with Professor Hongtan Liu in Chemical Engineering has led to a new approach to achieve more rapid oscillating conditions. Preparation of surface bound catalysts for carbonylation of diazo compounds will be tested in the lab and then incorported in a flow reactor system iconstructed so that pulsed flow conditions may achieve the desired oscillatory reaction conditions. Support of this work by ACS-PRF is gratefully acknowledged.