214049-97-5Relevant academic research and scientific papers
Electronic effects in the nickel-catalysed hydrocyanation of styrene applying chelating phosphorus ligands with large bite angles
Goertz, Wolfgang,Keim, Wilhelm,Vogt, Dieter,Englert, Ulli,Boele, Maarten D. K.,Van Der Veen, Lars A.,Kamer, Paul C. J.,Van Leeuwen, Piet W. N. M.
, p. 2981 - 2988 (1998)
Chelating phosphorus ligands with a rigid backbone and a large natural bite angle were applied in the nickel-catalysed hydrocyanation of styrene. The para substituents in the diphenylphosphanyl moiety of the 4,6-bis-(diphenylphosphanyl)-2,8-dimethylphenoxathiine (Thixantphos) ligands were varied and their electronic effects on the activity and selectivity of the catalytic experiments were investigated. The activity of the nickel complexes decreased when electron-donating substituents lead to a more basic phosphorus while electron-withdrawing substituents led to a higher activity. The results of variable temperature 31P-{1H} NMR experiments on the in situ catalysts are discussed in relationship to the catalytic performance. 4,6-Bis(diphenylphosphanyl)-2,8-dimethylphenoxathiine (Thixantphos) L1d and the complexes [NiCl2L1d] 1 and [Ni(CN)2L1a] 2 (p-Me2N on phenyl) have been characterised by single-crystal X-ray diffraction. Complex 2 represents the first crystal structure of a monomeric dicyanonickel(II) complex with a P-P chelating ligand. The geometries of ligand L1d and complex 1 were predicted by molecular mechanics calculations.
