Dichloro rhodium

Treatment of aqueous solutions of bis(ethylenediamine)dichloro-rhodium(III) with sodium borohydride give solutions which the proton magnetic resonance spectrum shows to contain an Rh—H complex (t 31 p.p.m., J Rh—h 31 c.p.s.). Also, the infrared spectrum of the precipitated tetraphenyl boronate shows a band at 2100 cm-1 assigned to an Rh—H stretch. 

Apart from ethanol, other primary alcohols catalyse the formation of the dichloro complex, probably via a rhodium(I) intermediate rather than a rhodium(III) hydride. Rhpy4X2" compounds have anti-bacterial activity. 

Phosphine, (2-bromophenyl)dichloro-, 2,991 Phosphine, (w-chloroalkyl)dichloro-, 2, 991 Phosphine, chlorodimethyl-, 2, 991 Phosphine, chloro(dimethylamino)-, 2, 991 Phosphine, chlorodiphenyl-, 2, 990 Phosphine, cyclohexyl(o-anisyl)methyl-rhodium complexes asymmetric hydrogenation, 6, 251 Phosphine, [(dialkylphosphino)alkyl]diphenyl-, 2, 994 Phosphine, dichloromethyl-, 2, 991 Phosphine, dichlorophenyl-, 2, 990 Phosphine, diethylphenyl-, 2, 992 Phosphine, dimethyl-, 2,992 Phosphine, dimethylphenyl-, 2,992 Phosphine, diphenyl-, 2, 992 Phosphine, ethyldiphenyl-, 2, 992 Phosphine, ethylenebis(diethyl-, 2, 993 Phosphine, ethylenebis(diphenyl-, 2,993 Phosphine, ethylenebis(phenyl-, 2,992 Phosphine, ethylidynetris[methylene(diphenyl-, 2,994 Phosphine, [(ethylphenylphosphino)hexyl]diphenyl-, 2, 994... 

Bis-[triphenylphosphin]-carbonyl-organo-rhodium(0) bzw. -iridium(O) sind aus den entsprechenden Dichloro-Komplexen bzw. Carbonyl-tris-[triphenyl-phosphin]-rhodium(0) bzw.-iridium(O) aus den Chloro-Komplexen zuganglich7 ... 

P-Chirogenic diphosphine 19, which rhodium-chelate complex forms a seven-membered ring (rare case for P-stereogenic ligand), was also prepared in reasonable yield (68%) using the wide chemistry of secondary phosphine borane [37]. Deprotonation of the enantiomerically enriched ferf-butylmethylphos-phine-borane 88 (Scheme 15) followed by quenching with a,a -dichloro-o-xylene and recrystallization afforded optically active diphosphine-borane 89 (precursor of free phosphine 19). 

For the synthesis of permethric acid esters 16 from l,l-dichloro-4-methyl-l,3-pentadiene and of chrysanthemic acid esters from 2,5-dimethyl-2,4-hexadienes, it seems that the yields are less sensitive to the choice of the catalyst 72 77). It is evident, however, that Rh2(OOCCF3)4 is again less efficient than other rhodium acetates. The influence of the alkyl group of the diazoacetate on the yields is only marginal for the chrysanthemic acid esters, but the yield of permethric acid esters 16 varies in a catalyst-dependent non-predictable way when methyl, ethyl, n-butyl or f-butyl diazoacetate are used77). 

The change in selectivity is not credited to the catalyst alone In general, the bulkier the alkyl residue of the diazoacetate is, the more of the m-permethric acid ester results 77). Alternatively, cyclopropanation of 2,5-dimethyl-2,4-hexadiene instead of l,l-dichloro-4-methyl-l,3-pentadiene leads to a preference for the thermodynamically favored trans-chrysanthemic add ester for most eatalyst/alkyl diazoacetate combinations77 . The reasons for these discrepandes are not yet clear, the interplay between steric, electronic and lipophilic factors is considered to determine the stereochemical outcome of an individual reaction77 . This seems to be true also for the cyclopropanation of isoprene with different combinations of alkyl diazoacetates and rhodium catalysts77 . 

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. 

The stmctural complexity and biological activity of the cyathane family of diterpenes has stimulated considerable interest from synthetic chemists, as reflected in the number and diversity of approaches reported thus far [42]. Our own strategy for cyathane synthesis is based on a rhodium-catalyzed [5+2] cycloaddition. The precursor for this reaction was fashioned ultimately from commercially available and inexpensive (S)-(-)-limonene. Treatment of the ketone 139 with 5 mol% [RhCl(CO)2]2 in 1,2-dichloro-ethane gave cycloadduct 140 (Scheme 13.14) in 90% yield and in analytically pure form after simple filtration through a plug of neutral alumina [43]. 

An example of the vinylogous reactivity is the reaction of 52 with cyclopentadiene (Tab. 14.9) [77]. Rhodium(II) acetate-catalyzed decomposition of 52 in dichloro-methane, yields a 2 1 mixture of the bicyclic system 53 derived from the [3-1-4] cycloaddition, and the bicyclo[2.2.1]heptene 54 resulting from electrophihc attack at the vinylic position followed by ring closure. When Rh2(TFA)4 is used as the catalyst, bicy-clo[2.2.1]heptene 54 becomes the dominant product, while the reactivity of the vinyl terminus is suppressed using a hydrocarbon solvent as observed in the Rh2(OOct)4-cat-alyzed reaction in pentane, which affords a 50 1 ratio of products favoring the [3-1-4] cycloadduct 53. 

Dichloro-tetrapyridino-rhodium Chloride, [Rh py4Cl2]Cl, is prepared by dissolving rhodium zinc in aqua-regia, and, after removal of acid, heating the aqueous solution with pyridine. On cooling, the pyridino-salt is deposited in yellow prisms. It melts when heated, yielding a black oil, and on further heating, metallic rhodium. 

Dichloro-tetrapyridino-rhodium Hydroxide, [Rh py4Cl2](OH), may be obtained from the chloride by grinding it with freshly precipitated silver oxide. The liquid so produced absorbs carbon dioxide from the air and liberates ammonia from ammonium salts. 

AMINES Chlorotris(triphenylphosphine)-rhodium(I). l,4-Dichloro-I,l,4,4-tetra-methyldisilethylene. 

If these preparations are carried out at high temperatures, or if either of the above complexes is heated, o-metallation occurs. No reduction to rhodium(I) complexes was observed265,266 It has been claimed that the attempted borohydride reduction of the dichloro complex in ethanol forms the unstable diamagnetic rhodium(II) complex [RhH(BH4) P(o-C6H4Me)3 ].212... 

A detailed stu of over 45 catalysts, primarily from Group VIII metal salts and complexes, showed palladium(II) compounds to be the most effective in the dehydrogenation of a variety of aldehydes and ketones. Soluble palladium(II) salts and complexes such as dichloro(tTiphenylphosphine)palladium(II) and palladium(II) acetylacetonate have been shown to be optimal, with the salts of rhodium, osmium, iridium and platinum having reduced efficacy. Since the d ydrogenation reaction is accompanied by reduction of the palladium(II) catalyst to palladium(0), oxygen and a cooxidant are required to effect reoxidadon. Copper(II) salts are favored cooxidants, but quinones, and especially p-benzoquinone, are also effective (Scheme 24). - ... 

Analogs of the dichloro complex are prepared by a variety of methods, many of which are specific for single compounds. The dibromo complexes can be prepared using nitrosyl bromide or from A-methyl-iV-nitrosotoluene-4-sulfonamide and rhodium tribromide. Replacement of the tribromide by the trichloride and an alkali metal iodide gives diiodo complexes (equations 50 and 51). 

Watts and coworkers reported the luminescence properties of cyclometalated iridium(III) and rhodium(III) complexes (see Cyclometalation). The dichloro-bridged dimers [M2(N C)4Cl2] (M = Ir, Rh HN C = Hppy, Hbzq) displayed intense emission with structural features in EtOH/MeOH/CH2Cl2 (4 1 1 v v) glass at 77 K. The emission of the rhodium(III) dimers was assigned to an lE excited state... 

Reactions of the dichloro-bridged rhodium(ni) and iridium(III) dimers with diimine ligands resulted iu the formation of the luminescent mononuclear complexes [M(N C)2(N N)]+ (M = Ir, Rh = ppy, bzq N N = bpy, phen). The electronic absorption and emission spectra of these complexes are shown in Figure 8. The rhodium(III) complexes displayed very long-lived emission in... 

Rhodium p,p-Dichloro-bis-[car-bonyl-chloro-methyl-(trime-thylphosphan)-...] XIII/9b, 348... 

C12H24CI404P2Rh2 Rhodium p, -Dichloro-bis-[acetyl-carbonyi-chloro-trimethyl-phosphan-...]- XIII/9h, 405... 

---