Coordination chemistry of diphenylphosphinoferrocenylthioethers on cyclooctadiene and norbornadiene rhodium(i) platforms

Abstract

Complexes [RhCl(diene)(P,SR)] with chiral ferrocenyl phosphine–thioethers ligands (diene = norbornadiene, NBD, 1^RRR, or 1,5-cyclooctadiene, COD, 3^RR; P,SR = CpFe(1,2-η⁵-C₅H₃(PPh₂)(CH₂SR); R = tBu, Ph, Bz, Et) and the corresponding [Rh(diene)(P,SR)][BF₄] (diene = NBD, 2^RR; COD, 4^RR) have been synthesized from [RhCl(diene)]₂ and the appropriate P,SR ligand. The molecular structure of the cationic complexes 2^tButtButttBu, 4^PhPh and 4^BzBzBz, determined by single-crystal X-ray diffraction, shows the expected slightly distorted square planar geometry. For the neutral chloride complexes, a combination of experimental IR and computational DFT investigations points to an equally four coordinate square planar geometry with the diene ligand, the chlorine and the phosphorus atoms in the coordination sphere and with a dangling thioether function. However, a second isomeric form featuring a 5-coordinated square planar geometry with the thioether function placed in the axial position is easily accessible in some cases.