RH-103 CHEMICAL-SHIFTS AND TRANS INFLUENCE OF LIGANDS IN RHODOXIMES AND ORGANORHODOXIMES

The Rh-103 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 wid e range of anionic ligands X, organo groups R and axial ligands L. The chemical shifts delta(103)Rh) in the halide complexes 1 show the 'nor mal halogen dependence' (Cl > Br > I). delta(Rh-103) in 2-6 depends on the axial base L in the order py > SMe(2) > PPh(3) > P(OPh)(3) approx imate to PMe(3) and in 2 on the organo group R in the order Et approxi mate to Me < Pr-n < CH(2)Ph approximate to CH(2)OMe < CH2Br < CH2Cl < Pr-i < Cy < CH = CH2 < CH(2)SiMe(3) < (t)Bu < cis-CH = CHPh approximat e to cis-CH=CHPr < Ph approximate to C = CPh < CPr = CH2. The coupling constants (1)J(Rh-103, P-31) in 2 reflect the (NMR) trans influence o f 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).