14N, 17O, 103Rh NMR studies of Rh(III) state in diluted nitric acid solutions

The state of rhodium(III) in nitric acid solutions diluted with 3M HNO3 or water was studied by N-14, O-17, and Rh-103 NMR methods. The Rh-103 NMR chemical shifts significantly depend on the ionic background of the solution. Concentrated nitric acid solutions (C-Rh = 0.5-1 mol/l) diluted 100 to 200 times retain the polynuclear Rh(III) forms with double (mu-NO3, mu-OH) bridges. The predominant form in the diluted solutions is a dinner.