Rhodium complexes perchlorate

A rhodium(III) perchlorate complex containing two molecules of the tritertiary arsine can also... 

The synthesis of the ds-tetraamminedichlororhodium(III) ion, using the reaction of tetraammine[oxalato]rhodium(III) perchlorate with boiling 6 M hydrochloric acid, was first reported in 1975. The oxalato complex is formed by the reaction of pentaamminechlororhodium(III) chloride with oxalate and oxalic acid in water at 120°. The synthesis has been repeated on numerous occasions in our laboratory, and we have found that only in a minority of cases is it possible to isolate [Rh(NH3)4(C204)]C104 H20 in sufficiently pure form to prepare the pure perchlorate by recrystallization. In a majority of cases the product that precipitates from the reaction mixture on addition of perchloric acid contains an appreciable quantity of an unidentified impurity that is not removed by recrystallization. The procedure given below permits the preparation of pure cis-[Rh(NH3)4Cl2]CH/2H20 from the latter crude, impure oxalato complex. 

Rhodium(5,5-Chiraphos)(NBD)] CIO4 (hicyclo[2.2.1]heptadiene)[(Z5,J5)-Z,3-his(diphenylphosplimo) hutane]-rhodium (I) perchlorate, [(l,2,5,6 )bicyclo[2.2.1]hepta-2,S-diene][5,5-1.2-dimethyl-l,2-ethanediyl)-his(diphenylphosphme)-P,P ]rhodium(l ) perchlorate [65012-74-0 65012-73-9 for cation Rh(S,S-chiraphos)(MeOH)2 has 71264-71-6] M 720.97. This catalyst can be prepared by two methods. In the first, 7% HCIO4 (0.173g, 1 equivalent) in THF (6ml) is added to a solution of the complex [Rh(NBD)(acac)] (0.356g) and 5, S -chiraphos (0.516g, see [64896-28-2]) in dry, freshly distilled, THF (7.5ml) under N2, and the deep red coloured solution is allowed to stand at 25° for 24 hours. The orange-red crystals that separate are collected, washed with cold THF, dried at 40° in vacuo to give the catalyst perchlorate (0.6g), which should be... 

Despite the above similarities, many differences between the members of this triad are also to be noted. Reduction of a trivalent compound, which yields a divalent compound in the case of cobalt, rarely does so for the heavier elements where the metal, univalent compounds, or hydrido complexes are the more usual products. Rhodium forms the quite stable, yellow [Rh(H20)6] " ion when hydrous Rh203 is dissolved in mineral acid, and it occurs in the solid state in salts such as the perchlorate, sulfate and alums. [Ir(H20)6] + is less readily obtained but has been shown to occur in solutions of in cone HCIO4. 

In our asymmetric process development, the discovery of the thermally stable rhodium bis-BINAP complex was outstanding as it enabled the repeated use of catalyst [10]. In Scheme 3, the synthesis of the cationic rhodium bis-Tol-BINAP complex 13 is illustrated. Its precursor 12 can be prepared quantitatively using cheap sodium perchlorate in a binary system in the presence of a phase transfer catalyst. It is possible to convert 12 to 13 by monitoring the reaction either by the volume of hydrogen absorbed or the color change from orange (12) to deep red (13). 

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