A) Positive ion ESI-MS spectra of rhodium (II) citrate: [Rh
+H]+ ( m/z 970,8). Ordinate: relative intensity. B) 13C NMR spectra of Rh
complex. The upper detail shows that the signals of α- and β-carboxyl carbon atoms in the complex (195.3 and 192.8 ppm, respectively) appear shifted.