Rhodium compounds Rh

H, can also be added under homogeneous conditions in solution by using transition-metal coordination complexes such as the rhodium compound, Rh[P(CftH,),Cl] (Wilkinson s catalyst). The relative rates of hydrogenation... 

Garbon-fluorine bonds of fluoroalkenes can be cleaved by reaction with metal hydrides to give HF and vinyl complexes. Thus, the rhodium compound [Rh (Z)-GF=GF(GF3) (PEt3)3] can be synthesized by regioselective G-F bond activation of hexafluoropropene at [RhH(PEt3)3] in the presence of Et3N/Gs2G03 (Scheme 10 left). ... 

Synthesis. The most important starting material for rhodium compounds is rhodium(III) chloride hydrate [20765-98-4], RhCl3 nH2 O. Other commercially available starting materials useful for laboratory-scale synthesis include [Rh2(0000113)4] [5503-41 -3], [Rh(NH3)201]0l2 [13820-95-6], [Rh20l2(0O)4] [32408-34-7], and [Rh20l2(cod)2] [12092-47-6]. 

Rhodium(III) hydroxide is an ill-defined compound Rh(0H)3.nH20 (n 3) obtained as a yellow precipitate by careful addition of alkali to Na3RhCl6-Addition of imidazole solution to suitable aqua ions leads to the precipitation of active rhodium(III) hydroxides formulated as Rh(0H)3(H20)3, Rh2(/x-0H)2(0H)4(H20)4 and Rh3(/z-0H)4(0H)5(H20)5 [31]. Hydrated iridium(III) hydroxide is obtained as a yellow precipitate from Ir3+ (aq.) at pH 8. 

M(NO)(OCOCF3)2(PPh3)2. Both these complexes have 5-coordinate geometries with monodentate carboxylates. The rhodium compound has a square pyramidal structure with bent Rh-N-O (122°) but the iridium compound has a tbp structure with straight equatorial Ir-N—O (178°). The position of i/(N—O) reflects this difference (1800 cm-1 (Ir) and 1665 cm-1 (Rh)). 

In the Li-Rh system LiRh is prepared from rhodium metal foil and liq Li in a 25 at% excess of the 1 1 molar ratio. The mixture is heated in an iron crucible to 750-880°C in Ar. The direct reaction of the elements in a molybdenum crucible at 800°C for 7 d produces LiRh. Identical methods produce Lilr and Lilrj with which the rhodium compounds are isostructural . The reaction of Rh metal with LiH at 600°C gives the ternary hydrides Li4RhH4 and Li4RhH5. 

Rhodium(I) complexes are effective reagents and/or catalysts for the decarbonylation of acyl halides and aldehydes 9 11,34,195,230,231,236). The compound Rh(PPh3)3Cl, especially, has received considerable attention. The first step in such reactions involves oxidative addition to Rh(I) of the organic molecule, exemplified by the following ... 

Chick embryos exposed to rhodium on the eighth day of incubation were stunted mild reduction of limb size and feather growth inhibition were also observed. A number of rhodium compounds have tested positive in bacterial assays for genetic altering capability. The 2003 ACGIH threshold limit valuetime-weighted averages (TLV-TWAs) are 1.0 mg/m for the metal, l.Omg/m as Rh, insoluble compounds, and 0.01 mg/m as Rh, soluble compounds. 

The first compound of the ammino-rhodium series examined was chloro-pentammino-rhodium chloride, [Rh(NH3)5Cl]Cl2, which vras prepared by treating rhodium trichloride with ammonia. Claus 1 investigated the composition of the substance and prepared from it, by means of moist silver oxide, a strongly basic substance, which proved to be the corresponding hydroxide, [Rh(NH3)5Cl](OH)2. 

Bromo-pentammino-rhodium Bromide, [Rh(NH3)5Br]Br2, is prepared in a similar manner to the cliloro-salt by heating rhodium-zinc alloy with a mixture of bromine and hydrobromic acid, or by warming aquo-pentammino-rhodium bromide with excess of hydrobromic acid to 100° C.1 2 It separates in small orthorhombic yellow crystals which are almost insoluble in cold water and insoluble in alcohol and hydrobromic acid. It has the same constitution as the ehloro-compound. Treated with nitric acid, hydrochloric acid, or silver carbonate, it yields the corresponding salts respectively, and with moist silver oxide yields an unstable hydroxide, [Rh(NIT3)5Br](OH)2. The methods from the preparation of the bromo-salts are like those for the ehloro-salts. 

Although this route also seemed to be suitable for rhodium compounds, the readily accessible complex [Rh(CHClMe)Cl(PPr,3)(775-C5H5)] did not afford the thioacetaldehyde complex when treated with NaHS but rather the vinyl complex [Rh(CH = CH2)Cl(PPri3)(775-C5H5)].55... 

---