Transition Metal NMR Spectroscopy. One‐bond ¹⁰³ Rh, ¹⁵ N coupling constants of axial and equatorial ligands in rhodoximes

Abstract

The 103Rh,15N coupling constants and 15N chemical shifts of XRhIII(Hdmg)2L rhodoximes (Hdmg=dimethylglyoximate, L=PPh3 or pyridine, X=halide, alkyl, haloalkyl) were extracted from gradient-selected (1H,15N)-HSQC experiments. Coupling between rhodium and the equatorial oxime nitrogens is large (18–21 Hz) and shows little sensitivity to the nature of the cis-oriented ligands X and L. In contrast, coupling between rhodium and the axial pyridine nitrogen is small (6–9 Hz) for X=alkyl but increases to 16–18 Hz in the halide complexes (‘trans influence’). The structural implications are discussed in conjunction with x-ray data. © 1997 John Wiley & Sons, Ltd.