Chloro rhodium® dimer

The dichlororuthenium arene dimers are conveniently prepared by refluxing ethanolic ruthenium trichloride in the appropriate cyclohexadiene [19]. The di-chloro(pentamethylcyclopentadienyl) rhodium dimer is prepared by refluxing Dewar benzene and rhodium trichloride, whilst the dichloro(pentamethylcyclo-pentadienyl)iridium dimer is prepared by reaction of the cyclopentadiene with iridium trichloride [20]. Alternatively, the complexes can be purchased from most precious-metal suppliers. It should be noted that these ruthenium, rhodium and iridium arenes are all fine, dusty, solids and are potential respiratory sensitizers. Hence, the materials should be handled with great care, especially when weighing or charging operations are being carried out. Appropriate protective clothing and air extraction facilities should be used at all times. 

Chloro-bridged dimeric rhodium(I) complexes, such as [Rh(CO)2Cl]2 (27, 57, 98) and [Rh(COD)Cl]a (25), react with polymeric resins to give monomeric polymer-bound complexes with phosphine and amine supports. 

The structure of 73 was substantiated spectroscopically (5 nB = 82.5 ppm) and confirmed crystallographically. A centrosymmetric chloro-bridged dimeric structure with tricoordinate copper centers was observed. The pendant character of the borane is apparent from the rather long the B- Cu (3.05 A) and B- Cl (4.06 A) distances associated with a trigonal planar geometry around boron. Compared to related mononuclear palladium and rhodium complexes (see Section IV.B), the presence of the chloro-bridge disfavors the formation of Cl-B interactions (coordination mode F) in 73. 

Chloro(norbomadiene)rhodium dimer, [RhCl(C7H8)]2. Mol. wt. 461.00, air-stable, golden yellow solid. Supplier Strem. 

QUINOLINES Chloro(norbornadiene)-rhodium dimer. Vilsmeier reagent. 

Siloxy-rhodium(I) complexes of general formula [(diene)Rh(//-OSiMe3)]2, where diene = cod, nbd, showed much higher catalytic activity in the hydrosilylation of 1-alkenes [50] and allyl ethers [51] by triethoxy silane than the respective chloro-rhodium(I) complexes [(diene)RhCw-Cl)2] suggesting a possible application of dimeric bridged siloxy-metal complexes as potent precursors of a variety of hydrosilylation reactions. 

Addition of trimethyl phosphite to benzene solutions of the chloro-bridged dimer [Rh(cod)Cl]a in the stoicheiometric amount 3 1 causes simultaneous bridge-splitting and olefin displacement, the final product being the monomeric species [Rh P(OMe)3 3Cl]. In the reaction with [Rh(CO)2Cl]2, trimethyl phosphite preferentially displaces one carbon monoxide at each rhodium atom and then proceeds to cleave the dimer. Further addition of phosphite causes displacement of chloride rather than carbon monoxide from /ra 5-[Rh(CO)- P(OMe)3 3Cl]. Both reactions can be followed using P H n.m.r. and i.r. spectroscopy, which enables a characterization of most of the species formed in solution. It is noteworthy that for the ratio P(OMe)3 Rh = 4 1 the spectra suggest the presence of five-co-ordinate [Rh(CO) P(OMe)3 4] which probably has a trigonal-bipyramidal structure with axial CO, ... 

The dimer of chloro(l,5-hexadiene)rhodium is an excellent catalyst for the room temperature hydrogenation of aromatic hydrocarbons at atmospheric pressure. The reaction is selective for the arene ring in the presence of ester, amide, ether and ketone functionalities (except acetophenone). The most useful phase transfer agents are tetrabutylammonium hydrogen sulfate and cetyltrimethylammonium bromide. The aqueous phase is a buffer of pH 7.6 (the constituents of the buffer are not critical). In all but one case the reaction is stereospecific giving cis products... 

Our study on the synthesis, structure and catalytic properties of rhodium and iridium dimeric and monomeric siloxide complexes has indicated that these complexes can be very useful as catalysts and precursors of catalysts of various reactions involving olefins, in particular hydrosilylation [9], silylative couphng [10], silyl carbonylation [11] and hydroformylation [12]. Especially, rhodium siloxide complexes appeared to be much more effective than the respective chloro complexes in the hydrosilylation of various olefins such as 1-hexene [9a], (poly)vinylsiloxanes [9b] and allyl alkyl ethers [9c]. 

Chloro(1,5 - cyclooctadiene)(tricyclohexylphosphine)rhodium-(I), RhCl(COD)(PCy3), Complex 17. The dimer [RhCl(COD)]2 (0.2 g) and PCy3 (1.6 g) were stirred in 10 mL CH2C12 for 10 min. The volume was reduced and diethyl ether was added to induce crystallization of the yellow product. We found carbon, 59.5 hydrogen, 8.4. C26H45ClPRh requires carbon, 59.3 hydrogen, 8.6. 

The first account on the carbonylation of heterocyclic compounds with metallo-dendrimers was recently reported by Lu and Alper using Rh-complexed dendrimers on a resin [207]. The building-block techniques of solid-phase chemistry were used to synthesize dendrimers, followed by phosphonation of the dendrimers with diphenylphosphinomethanol. The resulting phosphonated dendrimers were then reacted with chloro(dicarbonyl)rhodium(I) dimer to give dendritic catalysts A and B (31P NMR, 8 - 25 ppm loading of rhodium A, 0.74 mmol g-1 B, 0.83 mmol g ). As a model study, the reaction of l-ferf-butyl-2-phenylaziridine with carbon monoxide in catalytic presence of A afforded the desired [3-lactam... 

Perfluorobutadiene and dicarbonylchlororhodium(I) dimer react to give the chloro-bridged rhodium(III) dimer [(C4Fa)RhCl(CO)2]2 (181) with a metallocyclopentene ring similar to that in (C4Fe)Fe(CO)4 (71)... 

Diazopropenes bearing, for example, chloro substituents on the double bond can readily be purified by short-path distillation. Subsequent vinylcyclopropanations are carried out at low temperature using copper(II) catalysts such as bis(trifluoroacetonato)copper(II), copper(II) tri-fluorosulfonate and copper(II) trifluoroacetate in the presence of a 15-60-fold excess of the alkene. The dimer of rhodium(Il) acetate (0.1 mol%, tenfold excess of alkene), however, is generally more effective, leading to higher yields in this reaction (see Houben-Weyl, Vol. El9b, Table 100). 

Thiazolidines react with carbon monoxide in the presence of catalytic amounts of chloro (1,5-cycloctadiene)rhodium(I) dimer and potassium iodide to give 2-thiazoUdinones <94JA5662>. 

Rh02[As(CBH6)3]i +A"(A" = PFe" or ClOa"). This rhodium dioxygen complex is prepared by reaction of chloro(4,5-cyclooctadiene)rhodium(I) dimer (Strem) with triphenylarsine in the presence of oxygen (air) followed by addition of NHaPFe or LiClOa. ... 

Dichloro(T] -pentamethylcyclopentadienyl)rhodium(III) dimer di-p-chloro-dichlorobi (Ti -pentamethyl-... 

A 10-mL, flamed-dried, round-bottomed flask was charged with 10.0 mg of chloro(l,5-cyclooctadiene)rhodium(I) dimer (0.02 mmol), 33.0 mg (/ )-BINAP (0.053 mmol), and 500 (iL of 1,2-dichloroethane. The resulting solution was stirred at room temperature for 1 h. After 1 h, 481 pL of 1,2-dichloroethane and 174 pL of diethylmethylsilane (0.97 mmol) were added to the mixture, and the reaction vessel was stirred for 30 min. Next, 1.15 mL of stock benzaldehyde/phenyl acrylate solution (0.07 M in aldehyde and 0.84 M in acrylate, 0.81-mmol aldehyde, 0.97-mmol acrylate) was added dropwise to the solution. The vessel was then sealed and allowed to stir for 24 h. Solvent was then evaporated from the reaction mixture and 1 mL each of THF, MeOH, and 4 N HCl were added. This mixture was stirred at room temperature for an additional 30 min. Ethyl acetate was then used to extract the product (3x7 mL). The combined organic layers were washed with a saturated aqueous sodium bicarbonate solution (2 x 20 mL), dried over anhydrous MgS04, and filtered. The solvent was removed by rotary evaporation to yield crude product, which was purified via flash chromatography (9 1 then 5 1 hexanes ethyl acetate) to yield the product 298. 

The paper describes the first asym. hydroboration with a chiral catalyst. E A soln. of norbornene and catalytic amounts of chloro(l,5-cyclooctadiene)rhodium(I) dimer and DIOP (2,3-0-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane) in THF flushed with argon, stirred at 20° for 15 min, cooled to —78°, 1.2 eqs. catecholborane added, stirred for 5 min, allowed to warm to —40°, maintained at this temp, for 72 h, recooled to —78°, ethanol, 3 M NaOH, and 30% H2O2 added, the mixture allowed to warm to 25° during ca. 1 h, then stirred for 12h cjco-(lR, 2R)-norborneol. Y 99% (e.e. 55%). The method is generally applicable (even to 1,1-disubst. ethylene derivs. ) and expensive chiral boron-reagents are not necessary. F.e.s. K. Burgess, M.J. Ohlmeyer, J. Org. Chem. 53, 5178-9 (1988) from allyl alcohol O-derivs. s. Tetrahedron Letters 30, 395-8 (1989). 

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