RhCl

The use of silver fluoroborate as a catalyst or reagent often depends on the precipitation of a silver haUde. Thus the silver ion abstracts a CU from a rhodium chloride complex, ((CgH )2As)2(CO)RhCl, yielding the cationic rhodium fluoroborate [30935-54-7] hydrogenation catalyst (99). The complexing tendency of olefins for AgBF has led to the development of chemisorption methods for ethylene separation (100,101). Copper(I) fluoroborate [14708-11-3] also forms complexes with olefins hydrocarbon separations are effected by similar means (102). 

Compounds of most PGMs are only slightly to moderately toxic by oral ingestion (264), LD q (rat) RhCl, 1300 mg/kg Na2[IrCy, 500 mg/kg ... 

In 1943 the reaction of anhydrous RhCl and CO at 80°C under pressure with a haUde acceptor, such as copper, was reported to produce a black crystalline product formulated as Rh4(CO) (42). The correct stmcture of the complex was... 

The Wilkinson hydrogenation cycle shown in Figure 3 (16) was worked out in experiments that included isolation and identification of individual rhodium complexes, measurements of equiUbria of individual steps, deterrnination of rates of individual steps under conditions of stoichiometric reaction with certain reactants missing so that the catalytic cycle could not occur, and deterrnination of rates of the overall catalytic reaction. The cycle demonstrates some generally important points about catalysis the predominant species present in the reacting solution and the only ones that are easily observable by spectroscopic methods, eg, RhCl[P(CgH 2]3> 6 5)312 (olefin), and RhCl2[P(CgH )2]4, are outside the cycle, possibly in virtual equiUbrium with... 

RhCl(P(C3H3) 3) 3 + solvent RhCl(P(C3H3) 3) 2(solv) + P(C3H3) 3... 

RhCl(P(C3H3)3)2(solv) +H2 Rh(H)2Cl(P(C3H3)3)2(solv) where solvis solvent. An olefin, R, such as cyclohexene, substitutes for the solvent on the dihydride. 

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 . ... 

Tbe discovery of the catalytic properties of [RhCl(PPh3)3] naturally brought about a widespread search for other rhodium phosphines with catalytic activity. One of those which was found, also in Wilkinson s laboratory, was trans-[Rh(CO)H(PPh3)3 which can conveniently be... 

The paramagnetic impurity which invariably accompanies Wilkinson s catalyst has proved difficult to identify. It is probably the air-stable, green, irans- (RhCl(CO)(PPh3)2j- see K. R. Dunbar and S. C Harfner, Innrg. Chem. 31, 36"76-9 (1992),... 

Figure 26.4 The calalylic cycle for ihc hydrogenation of an alkene, catalysed by [RhCl(PPhj),] in benzene ...

Reaction of lithium 2,5-dimethylpyrrolate ion with [RhCl(CO)2]2 leads to formation of 84 (88PAC1193 90P1503). This is the first example of the mixed mode, when the ti N) and ti (C=C) coordination are realized simultaneously. Nucleophilic addition of triphenylphosphine and triphenylarsine gives 85 (E = P, As). The iridium analogs of 84 and 85 have also been synthesized. 

Complex formation with the Wilkinson catalyst RhCl(PPh3)3 gives 351 [870M(319)311]. The reaction with [Rh(Ti -C2H4)2Cl]2 gives the triple-decker... 

Interaction of // anj-[RhCl(CO)(/i,-dppm)]2 with pyrazolate ligands readily yields the so-called A-ftame complexes 175 (R = = H, X = Cl ... 

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