SummaryThe Io3Rh-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 signallnoise ratio is improved by the factor (T2/T;)"2 by this steady-state method in comparison with the usual freeinduction technique. The '03Rh-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 &scale, which extends over 10 000 ppm. For cyclic 173-diene ligands Rh-shielding increases with decreasing ring size and decreases with further conjugation of the diene systems.In the dirhodium complexes, Rh,Rh spin-coupling constants are < 10 Hz. Rh,Ccoupling constants in (diene)RhCp-complexes increase, for the terminal diene C-atom, with increasing ring size of the 1,3-diene, 'J(Rh,C)= 11.7 to 17.4 Hz.

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