103Rh chemical shifts and trans influence of ligands in rhodoximes and organorhodoximes

Abstract

AbstractThe 103Rh NMR chemical shifts of rhodoximes [Rh(dmgH)2(PPh3)X] (1) and organorhodoximes [Rh(dmgH)2(L)R] (2, L = PPh3; 3, L = PMe3; 4, L = P(OPh)3; 5, L = SMe2; 6, L = py) were measured with a wide range of anionic ligands X, organo groups R and axial ligands L. The chemical shifts δ(103Rh) in the halide complexes 1 show the ‘normal halogen dependence’ (Cl > Br > I). δ(103Rh) in 2–6 depends on the axial base L in the order py > SMe2 > PPh3 > P(OPh)3 ≈︁ PMe3 and in 2 on the organo group R in the order Et ≈︁ Me < nPr < CH2Ph ≈︁ CH2OMe < CH2Br < CH2Cl < iPr < Cy < CHCH2 < CH2SiMe3 < tBu < cis‐CHCHPh ≈︁ cis‐CHCHPr < Ph ≈︁ CCPh < CPrCH2. The coupling constants 1J(103Rh,31P) in 2 reflect the (NMR) trans influence of R. There is a strong correspondence between the NMR trans influence and the structural trans influence, as indicated by the bond lengths d(Rh—P).