Acrylate formation from CO2 and ethylene: catalysis with palladium and mechanistic insight.

We report the first catalyst based on palladium for the reaction of CO2, alkene and a base to form sodium acrylate and derivatives. A mechanism similar to a previously reported Ni(0)-catalyst is proposed based on stoichiometric in situ NMR experiments, isolated intermediates and a parent palladalactone. Our palladium catalyst was applied to the coupling of CO2 with conjugated alkenes.

Reaction of carbon dioxide with a palladium-alkyl complex supported by a bis-NHC framework.

The reactivity of a dimethyl palladium complex supported by a dicarbene chelate (MDC(Mes))PdMe(2) towards CO(2) has been investigated. In the presence of trace H(2)O, this reaction yields the corresponding methyl bicarbonate complex (MDC(Mes))PdMe(O(2)COH), which goes on to give the corresponding κ(2)-carbonato complex upon crystallization (MDC(Mes))Pd(CO(3)). This chemistry, as well as related protonolysis by acetic acid was monitored by a combination of techniques including React-IR spectroscopy.

Synthetic analogs for evaluating the influence of N-H...S hydrogen bonds on the formation of thioester in acetyl coenzyme A synthase.

A series of square planar methylnickel(II) complexes, (dppe)Ni(Me)(SAr) (dppe = 1,2-bis(diphenylphosphino)ethane); 2. Ar = phenyl; 3. Ar = pentafluorophenyl; 4. Ar = o-pivaloylaminophenyl; 5. Ar = p-pivaloylaminophenyl; (depe)Ni(Me)(SAr), (depe = 1,2-bis(diethylphosphino)ethane); 7. Ar = phenyl; 8. Ar = pentafluorophenyl; 9. Ar = o-pivaloylaminophenyl; 10. Ar = p-pivaloylaminophenyl), were synthesized via the reaction of (dppe)NiMe(2) (1) and (depe)NiMe(2) (6) with either the corresponding thiol or disulfide. These complexes were characterized by various spectroscopic methods including (31)P NMR, (1)H NMR, (13)C NMR and infrared spectroscopies and in most cases by X-ray diffraction analyses. Solid state and solution measurements establish that 4 and 9 contain intramolecular N-H...S bonds. Carbonylation of the complexes 2-4, 7-10 leads to (dRpe)Ni(CO)(2) and MeC(O)SAr via the intermediacy of the acylnickel adducts, (dRpe)Ni(C(O)Me)(SAr), detected at low temperature by (31)P NMR spectroscopy. Consistent with experimental observations, density functional theory results reveal that the intramolecular hydrogen bond in 9 stabilizes the acylnickel adduct compared with its non-hydrogen-bonded adduct, 10. Oxidative addition of MeC(O)SC(6)F(5) to (dRpe)Ni(COD) followed by spontaneous decarbonylation proceeds in variable yields generating 3 and 8.