Chiral bidentate aminophosphineligands: synthesis, coordination chemistry and asymmetric catalysis

Abstract

Chiral aminophosphines Ph₂PN(R)(CH₂)_nN(R)PPh₂1–4 [n = 2, R = CH(CH₃)(Ph) 1; n = 3, R = CH(CH₂CH₃)(Ph) 2, n = 2, R = CH(CH₃)(1-naphthyl) 3; n = 2, R = CH(CH₃)(C₆H₁₁) 4] were synthesized by the reaction of ClPPh₂ with the appropriate easily accessible enantiopure amine building blocks. For compounds 1 and 2, the corresponding selenides 5 and 6 were prepared to determine the electronic character of the phosphine moieties. By reaction of 1 with either PdCl₂(cod) or PdCl(CH₃)(cod) the cis-complexes 7 and 8 were obtained. The molecular structure for complex 7, cis-[PdCl₂(1)], was determined by X-ray crystallography. Reaction of PtCl₂(cod) with 1 or 2 yielded the corresponding monomeric cis-isomers 9 and 10. The rhodium derivative [RhCl(CO)(1)] (11) was obtained as a mixture of cis and trans-isomers. Preliminary results in the rhodium catalyzed hydroformylation of styrene and vinyl acetate, with ee's up to 51% and high regioselectivities, showed the potential of these chiral aminophosphines for homogeneous catalysis.