Hydroesterification catalysts

Platinum complexes have so far proved to be of only limited value as carbonylation catalysts. H2PtCl6 in the presence of SnCl2 acts as a hydroesterification catalyst for terminal alkenes (equation 141).5... 

Iridium with tributylphosphine like Co and Ru, is inferior to Rh as an ethylene hydroesterification catalyst. Palladium acetate gives no reaction. Propylene and other higher olefins react extremely slowly, even under optimum Rh tributylphosphine catalytic conditions. 

One can also envision that the quinone could trap the hydridopalladium species resulting from the B-hydrogen elimination that releases the oxidized organic product (Equation 16.129). Insertion of quinone into the palladium hydride would form an enolate that would tautomerize to the phenoxide complex. Protonation with the reagent containing an 0-H or N-H bond would generate the free hydroquinone and Pd(II). As noted in Chapter 17 on carbonylation, quinone has been used as an additive with this mechanism in mind to prevent tire Pd(II) hydroesterification catalysts from undergoing reduction to palladium(O). ... 

It is important to note that the hydrocarboxylation and carbonylation catalytic cycles involve common intermediates, but there are clear differences. In the hydrocarboxylation reaction, there is no oxidative addition or reductive elimination step, and all the intermediates have Rh. Other Fe-, Ru-, Co-, Rh-, Ir-, Pd-, and Pt-based hydrocarboxylation and/or hydroesterification catalysts are also known. Eastman Chemical has reported a Mo(CO)g-catalyzed ethylene hydrocarboxylation process that involves a radical mechanism. 

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