Nickel–heterocumulene complexes stabilized by trimethylphosphine: Synthesis, characterization and catalytic application in organozinc coupling with CS2

The reactivity of Ni(PMe3)4 with CO2, CS2 and SCNPh was studied. Although CO2 is structurally homologous compound with CS2 and SCNPh, its reactivity with Ni(PMe3)4 shows a different result with those of CS2 and SCNPh. Reactions of Ni(PMe3)4 with carbon disulfide and phenyl isothiocyanate in THF give the tetrahedral coordinate complexes (Me3P)3Ni(η2-CS2) (1) and (Me3P)3Ni(η2-SCNPh) (3), characterized by standard spectroscopic methods and X-ray diffraction. Nickel(0) complexes 1 and 3 are stabilized by the strong donor ligand PMe3. In the case of CO2, attempts to isolate the expected nickel(0) complex (Me3P)3Ni(η2-CO2) (4) proved to be unsuccessful. To further extend the utility of our nickel catalysts, the catalytic coupling of organozinc bearing different functionalities with CS2 was explored. With 10 mol% of 1 as the catalyst, MeZnMe, EtZnEt and PhZnBr coupled with CS2 to form the corresponding methyl dithiocarboxylate following esterfication of the initial products.

Reactions of Ni(PMe3)4 with carbon disulfide and phenyl isothiocyanate in THF give the tetrahedral coordinate complexes (PMe3)3Ni(η2-CS2) (1) and (PMe3)3Ni(η2-SCNPh) (3), characterized by standard spectroscopic methods and X-ray diffraction. Reaction of Ni(PMe3)4 with carbon dioxide results in the reduction of CO2 to CO, while trimethylphosphine served as reductant giving OPMe3. The catalytic coupling reactions of organozinc with CS2 were explored with complex 1 as catalyst.Figure optionsDownload as PowerPoint slideHighlights
► Reaction of heterocumulenes (CO2, CS2 and SCNPh) under mild conditions.
► C–S bond activation of carbon disulfide by nickel(0) complex, Ni(PMe3)4.
► C–S bond activation of phenyl isothiocyanate by nickel(0) complex, Ni(PMe3)4.
► Reduction of carbon dioxide to carbon monoxide by nickel(0) complex, Ni(PMe3)4.
► Catalytic coupling reactions of organozinc with carbon disulfide.