Rhodium chloride complexes

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). 

Bicyclo[2.2.1]hepta-2,5-diene rhodium (I) chloride dimer (norbornadiene rhodium chloride complex dimer) [12257-42-0] M 462, m 240°(dec). Recrystd from hot CHCl3-pet ether as fine crystals soluble in CHCI3 and C H but almost insoluble in Et20 or pet ether. [7 Chem Soc 3178 1959.]... 

P-31 NMR was a powerful tool in studies correlating the structure of tertiary-phosphine-rhodium chloride complexes with their behavior as olefin hydrogenation catalysts. Triphenylphosphine-rhodium complex hydrogenation catalyst species (1) were studied by Tolman et al. at du Pont and Company (2). They found that tris(triphenylphosphine)rhodium(I) chloride (A) dissociates to tri-phenylphosphine and a highly reactive intermediate (B). The latter is dimerized to tetrakis(triphenylphosphine)dirhodium(I) dichloride (C). 

The metathesis of vinyltri(alkoxy,methyl)silanes, reaction (17), proceeds smoothly at 60-130°C in the presence of ruthenium chloride complexes such as RuCl2(PPh3)3, or in some cases rhodium chloride complexes such as RhCl(PPh3)3,... 

Bicyclo[2.2.1]hepta-2 -diene rhodinm (I) chloride dimer (norbomadiene rhodium chloride complex... 

As shown in Scheme 168, oxidative addition reactions with either methyl chloride or methyl iodide proved successful and yielded the corresponding octahedral rhodium(III) complexes. ... 

When irradiated in the presence of norbornadiene and high-pressure synthesis gas, rhodium chloride is converted to a catalyst which is active for a variety of reactions. /2A/. The salt is probably converted photochemically to the rhodium norbornadiene complex 9. This dimer may undergo a consecutive photoreaction to give the monomeric hydrido complex 10, which is the actual catalyst for polymerisation, hydrogenation, and hydroformylation reactions. 

Remarkably, Claver et al. showed that in a square planar rhodium carbonyl chloride complex, two bulky phosphite ligands (65) were able to coordinate in a trans orientation.214 Diphosphite ligands having a high selectivity for linear aldehyde were introduced by Bryant and co-workers. Typical examples are (67)-(70).215,216... 

Dimeric chloride initiators, 14 267 Dimeric fullerenes, 12 233, 252 Dimeric Lewis acids, 14 267 Dimeric rhodium isocyanide complexes, 19 648... 

Am(m)ine and pyridine complexes such as mer-[RhCl3(NH3)3] (45) were the first rhodium(III) complexes to be tested because they contain cis-chloride ligands as does cisplatin (213). Complex 45 displays a positive dose-response relationship against several tumor cells such as Sarcoma 180. 

Almost all stable carbenes behave as 2-electron-CT-donating ligands with a few exceptions. In particular, in almost all cases corresponding Rh(I) complexes were targeted due to the easy synthetic method. An exception is the cyclopropenylidene carbene, with an extremely acute carbene angle. In this case, a second equivalent of carbene squeezes into the rhodium center, eliminating a chloride anion, giving the cationic dicarbenic rhodium(l) complex [51] (Scheme 5). 

We would have thought the same thing after some studies of the competition between chloride, bromide, and iodide for some rhodium(III) complexes, because we found that the ratios of the rate constants at 50°C. were very nearly 1 1 1. However, when activation energies were measured, we found that these produce a much bigger discrimination. In fact, the activation energy for the addition of iodide to our reactive intermediates is no less than 6 kcal. greater than the activation energy for addition of chloride and bromide. 

The nature of the support can have a very profound influence on the catalyst activity. Thus, phosphinated polyvinyl chloride supports are fairly inactive (75), and phosphinated polystyrene catalysts are considerably more active (57), but rather less active particularly when cyclic olefins are the substrates than phosphinated silica supports (76). Silica-supported catalysts may be more active because the rhodium(I) complexes are bound to the outside of the silica surface and are, therefore, more readily available to the reactants than in the polystyrene-based catalysts where the rhodium(I) complex may be deep inside the polymer beads. If this is so, the polystyrene-based catalysts should be more valuable when it is desired to hydrogenate selectively one olefin in a mixture of olefins, whereas the silica-based catalysts should be more valuable when a rapid hydrogenation of a pure substrate is required. 

The addition of olefins to olefins426 can also be accomplished by bases427 as well as by the use of catalyst systems428 consisting of nickel complexes and alkylaluminum compounds (known as Ziegler catalysts), 29 catalysts derived from rhodium chloride,430 and other transition metal catalysts. These and similar catalysts also catalyze the 1,4-addition of olefins to conjugated dienes,431 e.g.,... 

The reaction of bis-phenylpropargyl ether (321) with tris(triphenylphosphine)rhodium chloride in benzene or toluene led to the formation of the unusual organometallic compound (322), which can be viewed as a derivative of an oxygen-rhodium pentalene system. Reaction of the rhodium complex (322) with sulfur leads to the corresponding 4,6-diphenyl-l,3-dihydro[3,4-c]furan (323). The selenium and tellurium analogs (324) and (325) were made in a similar manner (Scheme 111) (76LA1448). 

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