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

Carl D. Hoff, PhD, University of Miami

Carbonylation reactions of trimethylsilyl diazomethane have been reported for Co2(CO)81 and [(h5-C5Me5)(CO)3Cr ]22 and the hetereonuclear metal-metal bonded dimer (h5-C5Me5)(CO)3Cr-Co(CO)4  was prepared according to eqn. (1):

The mixed metal dimer appears to react more rapidlywith trimethylsilyl diazomethane yielding the corresponding ketene but it is prone to decarbonylation in situ to yield a cluster which can be formulated as {[Cp*Cr](Co2(CO)7)}2 the structure of which is shown in Figure 1.

Figure 1. Structure of {[Cp*Cr](Co2(CO)7)}2 The more rapid catalytic properties of the mixed metal dimer are attributed to the presence of small equilibrium amounts of the ·Cr(CO)3C5Me5 radical present in solution serving as an initator and more facile subsequent CO transfer in the presence of CO bound to Cobalt. Attempts to study this under higher CO pressure are underway. Initial progress in construction of the oscillating pressure reactor met with barriers in terms of the rate of gas exchange in the original reactor design, A new system has been designed and the intial high pressure manifold built. A no-cost extension has been requested to allow completion of the construction and testing of this equipment which is ongoing at this time. The metal system is now based on use of a cylindrical metal reactor modeled by the glass system shown below. The toluene solvent is filled with small glass beads which have a hole in the center. As shown on the left when the reactor is idle gas exchange would be slow. High speed photography (1/1000 of a second) shows that when placed on the centrifugal mixer the solution is dispersed to a film with the glass beads turning it into essentially a mist. Experimental and computational aspect of mixing are in progress with Professor Liu and his students in Engineering and indicate that a gas exchange time on the order of one second is obtainable in this design.

Figure 2. Mixing CO under 2 atm pressure by hollow bead dispersion The picture at the left of Figure 2 shows the solution at rest showing one larger yellow and blue bead for tracking the trajectory. Both can be seen in the active stirring mode on the right with the yellow bead above the blue bead. Tracking shows relatively random motion of the two balls and exceptional solution mixing in formation of essentially a mist. Finally, application of this system to asymmetric hydroformylation with Professor Clark Landis at the University of Wisconsin is planned to begin when reactor construction is finalized. Two manuscripts are nearing completion over the reactor design and modeling and over the mixed metal ketene carbonylation system. The authors thank ACS-PRF for support of this project.