Spin-tickling technique for the indirect measurements of the Rh-103 NMR parameters of organo-rhodium compounds

Abstract

The extremely low gyromagnetic ratio of the Rh-103 nucleus hampers the measurement of NMR spectra via direct observation, particularly on a low-field spectrometer. In this study our approach has been to use the high sensitivity of the P-31 nucleus to obtain Rh-103 chemical shifts by the spin-tickling method, using a low field 1.4T, 60 MHz spectrometer. In addition to determining the Rh-103 chemical shifts, this type of experiments provide the relative signs of the coupling and reduced coupling constant. The compounds Ph2PLi, (MeO)(2)PCH2CH2P(OMe)(2) (L-L) [(Cod)Rh-(mu(2)-Cl)](2), [(Cot)Rh(mu(2-)Cl)](2), [(Cod)(2)Rh-2(mu(2)-Ph2P)(2)] (I), [(Cod)Rh-A(mu(2)-Ph2P)(2)Rh-B(Ph3P)](2) (II), [(Cod)Rh-A(mu(2)-Ph2P)(2)Rh-B (Ph3As)](2) (III) and [(MeO)(2)PCH2CH2P (OMe)(2)Rh(mu(2)-Cl)](2) (IV) were prepared. The NMR parameters of the organo-rhodium compounds J(Rh-P), J(Rh-Rh), delta(Rh-103) with their relative signs and the reduced coupling constants were investigated.