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

The 103 Rh NMR chemical shifts of rhodoximes [Rh(dmgH) 2 (PPh 3 )X] ( 1 ) and organorhodoximes [Rh(dmgH) 2 (L)R] ( 2 , L = PPh 3 ; 3 , L = PMe 3 ; 4 , L = P(OPh) 3 ; 5 , L = SMe 2 ; 6 , L = py) were measured with a wide range of anionic ligands X, organo groups R and axial ligands L. The chemical shifts δ( 103 Rh) in the halide complexes 1 show the ‘normal halogen dependence’ (Cl > Br > I). δ( 103 Rh) in 2–6 depends on the axial base L in the order py > SMe 2 > PPh 3 > P(OPh) 3 ≈ PMe 3 and in 2 on the organo group R in the order Et ≈ Me < n Pr < CH 2 Ph ≈ CH 2 OMe < CH 2 Br < CH 2 Cl < i Pr < Cy < CHCH 2 < CH 2 SiMe 3 < t Bu < cis ‐CHCHPh ≈ cis ‐CHCHPr < Ph ≈ CCPh < CPrCH 2 . The coupling constants 1 J ( 103 Rh, 31 P) 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).