Edmund J. Mozeleski

High-pressure NMR studies of the water soluble rhodium hydroformylation system

Rh(CO)2(acac) reacts with P(m-C6H4SO3Na.H2O)3 (P/Rh > 3.5) in water under CO to give HRh(CO)[P(m-C6H4SO3Na)3]3 (1a), the structure of which is similar to HRh(CO) (PPh3)3 (1b). High pressure NMR spectra of an aqueous solution containing1a and three molar excess of P(m-C6H4SO3Na)3 does not show the formation of new species up to 200 atm of CO∶H2(1∶1). In contrast,1b, in the presence of three molar excess of PPh3, is completely converted to HRh(CO)2(PPh3)2 (2b) under 30 atm CO/H2(1∶1) in toluene. The activation energy of the dissociation of P(m-C6H4SO3Na)3 from1a in water was found to be 30±1 kcal/mol, which is 11±1 kcal/mol higher than the dissociation of PPh3 from1b in toluene.

Supported ionic liquid catalysis investigated for hydrogenation reactions

The concept of supported ionic liquid catalysis (silc) has successfully been applied to hydrogenation reactions, which significantly reduced the required amounts of ionic liquid phase and enabled the usage of fixed-bed technology; the resulting catalysts exhibited high activity and outstanding stability.

Steric Effects on the Synthesis, Structure, Reactivity and Selectivity of t-Phosphine Rhodium Complex Hydroformylation Catalysts

Abstract Bulky trivalent phosphorus ligands of transition metal complexes were often observed to affect catalyst activity and selectivity. In the area of the low pressure hydroformylation of α-olefins in the presence of rhodium complexes, Pruett and Smith observed early (1) that the use of bulky ortho-substituted phosphite ester ligands leads to a decrease of the ratio of straight chain versus branched aldehyde products (n/i ratio). More recently van Leeuwen and Roobek have shown (2) that rhodium complexes of such bulky ligands are much more active catalysts than the much studied triphenylphosphine-rhodium catalyst system, in the hydroformylation of linear internal and branched terminal olefins. They suggested that for steric reasons only two bulky ligands could be coordinated to the same rhodium in such complexes and that such ligands could increase the coordinative unsaturation of rhodium, thus leading to a higher reactivity. Indeed a number of coordinatively unsaturated rhodium carbonyl complexes of bu...

13C NMR study of the acid-catalyzed carbonylation of methyl tert-butyl ether (MTBE)

Methyl tert-butyl ether (MTBE) is a widely used additive in oxygenated gasoline that has recently been identified as a potential health threat to the drinking water supply due to leaking underground storage tanks. One alternate use for MTBE is the production of methyl 2,2-dimethylpropanoate (methyl pivalate) via Koch carbonylation chemistry. BF3/H2O catalysts are employed in industrial applications of Koch chemistry, but cannot be used for direct ester production because the presence of water in the system leads to the formation of carboxylic acids and lowers the selectivity to esters. Therefore, a BF3/CH3OH complex was investigated for the carbonylation of MTBE to avoid this loss in selectivity. This study used 13C NMR spectroscopy and ab initio calculations to investigate this carbonylation reaction. NMR results and ab initio calculations suggest a structure for the BF3/CH3OH acid which is in agreement with previous studies, and a Hammett acidity value of -4.2 was calculated for BF3-2.19CH3OH using the Δδ method. It is believed that these are the first reported ab initio calculations on the BF3/CH3OH system. NMR results also show that MTBE begins to react between 50 °C and 75 °C to produce oligomers of isobutene when no CO is present and carbonylated species when CO is present.