Synthesis and characterization of ether-derivatized aminophosphines and their application in C–C coupling reactions

Four new bis(phosphino)amine ligands (Ph2P)2N-C6H3-R, where R = 3,5-OMe (1), 2,5-OMe (2), 2,4-OMe (3) or 3,4-OMe (4), were prepared via aminolysis of the corresponding dimethoxyanilines with 2 equiv. of diphenylphosphine chloride in the presence of triethyl amine. Oxidation of these ligands with aqueous H2O2, elemental S8 or Se powder afforded the corresponding chalcogen oxides 1a–4a, sulfides 1b–4b and selenides 1c–4c in good yields. Reaction of 1–4 with [MCl2(cod)] (M = Pt, Pd; cod = cycloocta-1,5-diene) in equimolar ratios afforded cis-[MCl2{(Ph2P)2N-C6H3-R}] (M = Pt; R = 3,5-OMe 1d, R = 2,5-OMe 2d, R = 2,4-OMe 3d, and R = 3,4-OMe 4d. M = Pd; R = 3,5-OMe 1e, R = 2,5-OMe 2e, R = 2,4-OMe 3e, and R = 3,4-OMe 4e). Similarly, reaction of [Cu(CH3CN)4]PF6 with the 1–4 in 1:2 ratio gave [Cu{(Ph2P)2N-C6H3-R}2]PF6 (R = 3,5-OMe 1f, 2,5-OMe 2f, 2,4-OMe 3f and 3,4-OMe 4f). All new compounds were fully characterized by spectroscopy and elemental analysis and the molecular structures of seven representative compounds were determined by single-crystal X-ray crystallography. In addition, the palladium complexes were investigated as pre-catalysts in C–C coupling reactions.