Daniela Cozzula

A Unique Palladium Catalyst for Efficient and Selective Alkoxycarbonylation of Olefins with Formates

Forget about CO! Carbonylations are among the most important homogeneously catalyzed reactions in the chemical industry, but typically require carbon monoxide. Instead, straightforward and efficient alkoxycarbonylations of olefins can proceed with alkyl formates in the presence of a specific palladium catalyst. Aromatic, terminal aliphatic, and internal olefins are carbonylated to give industrially important linear esters at low catalyst loadings.

The microstructure and melt properties of CO-ethylene copolymers with remarkably low CO content†

Polyketones with low CO content and molecular weight in the oligomer range were obtained with unprecedented efficiency by using a new protocol for the palladium-catalysed copolymerisation of CO and ethylene. Key physicochemical properties such as resistance to degradation and melting point were traced back to the microstructure of the polyketones. With properties tailored to the application, non-alternating polyketones emerge as interesting materials for demanding applications, where alternating polyketones are currently being used. Furthermore, the keto groups constitute interesting anchoring sites for introducing functionalities.

Directing the Cleavage of Ester C−O Bonds by Controlling the Hydrogen Availability on the Surface of Coprecipitated Pd/Fe3O4

The ready availability of esters from natural sources makes them promising substrates for the sustainable production of key intermediates of the chemical industry. In this context, methods to selectively cleave the alkoxy or ester C−O bond to obtain either alkane+acid or alcohol+aldehyde were investigated. Using Pd/Fe3O4(r) [(r)=reduced] as the catalyst of choice and either 2‐propanol—as indirect H source—or molecular hydrogen—as ample H source—the hydrogen coverage on the surface of the catalyst was controlled. This enabled selective cleavage of either the alkoxy C−O bond or the ester C−O bond in aromatic esters as shown for the hydrogenolysis of 2‐phenylethylacetate as model substrate. Noteworthy, hydrogenation of the aromatic ring was not observed. Thus, an exceptionally high chemoselectivity of Pd/Fe3O4(r) to hydrogenolysis of the ester group is combined with the option to readily direct the regioselectivity.

A DFT Study on the Co-polymerization of CO2 and Ethylene: Feasibility Analysis for the Direct Synthesis of Polyethylene Esters

The co-polymerization of CO2 with the non-polar monomer ethylene, though highly desirable, still presents a challenge whereas the palladium-catalyzed CO/C2 H4 co-polymerization is well understood. Building on this analogy, the goal of this study was to elucidate the feasibility of developing suitable catalysts for co-polymerizing CO2 with ethylene to polyethylene esters. Computational methods based on density functional theory were hereby employed. In the search for new catalyst lead structures, a closed catalytic cycle was identified for the palladium-catalyzed CO2 /C2 H4 co-polymerization reaction. The computational study on palladium complexes with a substituted anionic 2-[bis(2,4-dimethoxyphenyl)-phosphine]-benzene-2-hydroxo ligand revealed key aspects that need to be considered when designing ligand sets for potential catalysts for the non-alternating co-polymerization of CO2 and ethylene.

Isocyanurate formation during rigid polyurethane foam assembly: a mechanistic study based on in situ IR and NMR spectroscopy

An in-depth exploratory study on the mechanism of isocyanurate formation during the assembly of rigid PU/PIR polyurethane foams was performed thereby unravelling the role and working principle of the catalyst. Mimicking the complex pattern of the foam with mono-functional equivalents, the pathways to isocyanurate formation were investigated. Reactions focusing on potassium acetate as benchmark catalyst were thereto followed by in situ IR and NMR spectroscopy. Two pathways to isocyanurate formation from isocyanates were revealed: a one-component route via cyclotrimerization and a two-component route via carbamate and allophanate. We show that in the presence of alcohol and along with the formation of carbamate, isocyanurate is formed preferentially according to the two-component route in three consecutive steps. Allophanate, which in this study was isolated and characterized, is formed in situ in small transient concentrations from carbamate and the excess of isocyanate. For the first time it is proven that the allophanate intermediate undergoes an addition–elimination step with nucleophilic species to provide the isocyanurate.

The distinct role of the flexible polymer matrix in catalytic conversions over immobilised nanoparticles

Polymer resins with immobilized metal nanoparticles represent highly promising materials for attaining intelligent and ecologically friendly catalysts. Control of the dynamic swelling behaviour of the polymer resins enables the on/off-switching of the activity of the encapsulated metal nanoparticles, thereby allowing conversion and selectivity to be controlled at a specific time of the chemical reaction. This paper presents a study on the distinct role of the polymer support. Here, the hydrogenation of nitrobenzene was chosen as a model reaction, and nanoparticles of different metals were taken into account. The course of the reaction revealed the essential role of the polymer resins in controlling the diffusion, in particular of the reagents, to and from the catalytically active sites on the surface of the nanoparticles thereby influencing the catalytic activity of the metal and opening up a new approach to catalytic engineering.