Rhodium paramagnetic complexes

The Mononuclear Carbonyls When exchanged into the zeolite as Rh(NH )jCll-z+, the rhodium ammine complex could decompose in an oxygen stream at temperatures ranging 150-350°C into a rhodium Ill-hydroxy-species with a partial reduction into diamagnetic Rh(I) and paramagnetic (less than 10%) Rhll species. 

Equilibration with carbon monoxide at room temperature and low pressure (a few torr ) yielded the rhodium(I)-dicarbonyl compound (13) in addition to the Rh(I)(C0) paramagnetic complexe (11). The structure of this complex was elucidated by ESCA and UV measurements (13) which showed that the trivalent rhodium was indeed reduced to the monovalent state and by infrared spectroscopy which provided evidence for a gem dicarbonyl (14). Use of 1 1 C0 ... 

Many large tertiary phosphines fail to reduce hydrated rhodium trichloride and form rhodium(I) complexes. Under mild conditions they usually reduce the salt to paramagnetic rhodium(II) complexes. This was first discovered when P(o-C6H4Me)3 was employed, as in equation (92).26S... 

The closely related ligand, PBu2(o-C6H4OMe), also forms a paramagnetic rhodium(II) complex. However, in the reaction the ligand is demethylated, and the product has a totally different structure to the halo complexes so far described in this section.273... 

A similar reaction takes place between RhCl3 3H20 and the keto phosphine PBu2(CH2COPh), except that a rhodium(III) complex is first formed containing the phosphaenolate. In the presence of sodium methoxide this rhodium(III) complex is reduced to the paramagnetic rhodium(II) species (30).274... 

A,A-dialkyldithiocarbamates produce stable, square-planar rhodium(II) complexes of the type [Rh(S2CNR2)2] (R = Me, Et) similar anionic hfr(maleonitriledithiolate) are also known. Neutral complexes are formed by the thiol containing amino acids cysteine, methyl cysteine, or penicillamine. It is noteworthy that these paramagnetic [Rh(aminoacid)2] complexes can easily be prepared from dimeric, diamagnetic [Rh(02CMe)2MeOH]2. ... 

The complexes [Rh°(TMP)], [Rh°(TTEPP)], [Rh (TTiPP)], [Ir°(TTEPP)], and [Ir°(TTiPP)] are sufficiently bulky to completely prevent dimerization (TMP = tetramesitylporphyrinato TTEPP = tetra(2,4,6-triethylphenyl)porphyr-inato TTiPP = tetra(2,4,6-triisopropyl- phenyl)porphyrinato). The EPR spectroscopy, NMR paramagnetic shifts and line-broadening studies have proven useful to smdy the structme and reactivity of these paramagnetic complexes (and their adducts with ethene and CO, see below) (133-135). The EPR parameters of the rhodium complexes [Rh (TMP)J and [Rh TTiPP)] are... 

Similarity with cobalt is also apparent in the affinity of Rh and iH for ammonia and amines. The kinetic inertness of the ammines of Rh has led to the use of several of them in studies of the trans effect (p. 1163) in octahedral complexes, while the ammines of Ir are so stable as to withstand boiling in aqueous alkali. Stable complexes such as [M(C204)3], [M(acac)3] and [M(CN)5] are formed by all three metals. Force constants obtained from the infrared spectra of the hexacyano complexes indicate that the M--C bond strength increases in the order Co < Rh < [r. Like cobalt, rhodium too forms bridged superoxides such as the blue, paramagnetic, fCl(py)4Rh-02-Rh(py)4Cll produced by aerial oxidation of aqueous ethanolic solutions of RhCL and pyridine.In fact it seems likely that many of the species produced by oxidation of aqueous solutions of Rh and presumed to contain the metal in higher oxidation states, are actually superoxides of Rh . ... 

The complex ion (Figure 2.32) contains Rh2 bound cis to two phosphorus atoms (2.216 A) and more distantly to four oxygens (2.201—2.398 A), exhibiting a distortion ascribed to the Jahn-Teller effect it is paramagnetic (fi = 1.80 fiB) and exhibits an ESR spectrum (Figure 2.33) showing rhodium hyperfine coupling as the doublet for g. ... 

The rhodium(II) compound is a diamagnetic dimer with oxygen it forms a paramagnetic monomeric 02 adduct, probably a superoxide complex represented as (porph)Rh3+02. 

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