AbstractThe103Rh‐resonance has been investigated at 2.8 MHz in mono‐ and dinuclear olefin complexes by steady‐state NMR.‐pulse techniques. For dirhodium complexes with scalar Rh, Rh‐coupling, a selective rf‐irradiation was applied to improve sensitivity. Within the same measuring time the signal/noise ratio is improved by the factor (T2/T 2*)1/2by this steady‐state method in comparison with the usual free‐induction technique. (T1/T2)‐ratios, as obtained from the dependence of signal in tensity on the pulse‐flip angle are discussed in terms of relaxation mechanisms and chemical exchange phenomena. From (T1/T2)‐ and (T1+ T2)‐experiments, individual T1and T2values have been determined for C5H5RhC8H12and Rh(acac)3.The 103Rh‐chemical shifts of 39 olefin complexes are reported. Shielding depends upon the (formal) oxidation state of Rh whereby resonances of pure olefin complexes appear at the low‐frequency end of the δ‐scale, which extends over 10000 ppm. For cyclic 1,3‐diene ligands Rh‐shieldingincreaseswithdecreasing ringsize anddecreaseswith further conjugation of the diene systems.In the dirhodium complexes, Rh, Rh spin‐coupling constants are<10 Hz. Rh, C‐coupling constants in (diene)RhCp‐complexes increase, for the terminal diene C‐at om, with increasing ring size