Synthesis and coordination to Rh and Co of methylene-bridged diphosphines designed for asymmetric hydrogenation

Abstract

In this TREBALL DE FI DE GRAU (TFG), a new one-pot synthetic method to obtain methylene-bridged diphosphines bearing only one P-stereogenic moieity is described. Using this method, the ligand L1 was synthesised as proof of concept from a P-stereogenic methylmonophosphine-borane, obtained previously in the group. Four other diphosphines (L2-L5) were synthesised by a published method and three of them complexed to Rh(I) giving four complexes, C2, C4, C2-CO, C3-BIS, which were fully characterised. Preliminary, in situ complexation studies of the four diphosphines with Co were also performed.The Rh(I) complexes as well as diphosphine ligands were found to be unstable in air, so they were synthesised under inert atmosphere. Two types of Rh(I) complexes, monochelated and bisquelated were isolated. Cobalt(I) complexes are known to be very air-sensitive, hence their syntheses were performed in a dry box also under inert atmosphere. The complexes have been used as catalytic precursors in the hydrogenation of benchmark substrates S1-S3.