Rhodium hydridotetrakis

Rhodium, hexakis(trifluorophosphine)di-, 4, 905 Rhodium, hydridobis(diphenylphosphinoethane)-, 4, 924 Rhodium, hydridotetrakis((butylidynetrimethylene)-phosphite)-, 4, 921... 

Rhodium, hydridotetrakis(triphenyl phosphite)-, 4,923 Rhodium, hydrido(trifluorophosphine)tris-(triphenylphosphine)-, 4,921 Rhodium, hydrido(triphenylarsine)tris-(triphenylphosphine)-, 4,921,924 Rhodium, hydridotris(triphenylphosphine)-, 4, 916 preparation, 4, 916... 

The first example involving a rhodium catalyst in an ene reaction was reported by Schmitz in 1976. An intramolecular cyclization of a diene occurred to give a pyrrole when exposed to rhodium trichloride in isobutanol (Eq. 2) [15]. Subsequently to this work, Grigg utilized Wilkinson s catalyst to effect a similar cycloisomerization reaction (Eq. 3) [16]. Opplozer and Eurstner showed that a n -allyl-rhodium species could be formed from an allyl carbonate or acetate and intercepted intramolecularly by an alkene to afford 1,4-dienes (Eq. 4). Hydridotetrakis(triphenylphosphine)rhodium(l) proved to be the most efficient catalyst for this particular transformation. A direct comparison was made between this catalyst and palladium bis(dibenzylidene) acetone, in which it was determined that rhodium might offer an additional stereochemical perspective. In the latter case, this type of reaction is typically referred to as a metallo-ene reaction [17]. 

The Hydrogenation of 1-Hexene Catalyzed by Solutions of Hydridotetrakis(Triphenyl-phosphine)Rhodium(I)... 

This makes it easy to predict that solutions of HRh(PPh3)4 are more active catalysts than solutions of HRh(CO) (PPh3)3, either because the concentration of coordinatively unsaturated complexes increases or because the rate constant of the oxidative addition of hydrogen increases. A kinetic investigation of the hydrogenation of hexene catalyzed by solutions of hydridotetrakis( triphenylphosphine) rhodium (I) is reported here. 

Hydridotetrakis(triphenylphosphine)-rhodium(I), 144 N-Lithioethylenediamine, 157 Trimethylsilyl trifluoromethanesulfo-nate, 329... 

Metal-containing compounds, Rhodium Compounds (Continued) Hydridotetrakis(triphenylphosphine)-rhodium(I), 144 Rhodium(II) acetate, 226, 266 Rhodium(II) carboxylates, 226, 266 Rhodium(II) trifluoroacetate, 266 Tetra-jx3-carbonyldodecacarbonylhexa-rhodium, 152, 288... 

Acetic acid (1.0 mL) is added to a suspension of hydridotetrakis(tri-phenylphosphine)rhodium (0.58 g) in ethanol (15.0 mL), and the mixture is heated under reflux for 15 min. During this time the starting material dissolves and orange crystals are deposited. The mixture is cooled the crystals are filtered off, washed successively in methanol (2 x 10 mL), water (2 x 10 mL), and methanol (2 x 10 mL), then dried in vacuo. 

The hydridotetrakis(triphenyl phosphite)rhodium complex described below is the first example of a rhodium hydride complex stabilized by phosphite ligands.2... 

Hydridotetrakis(triphenylphosphine)rhodium(I) has previously been prepared by addition of triphenylphosphine to preformed hydridotris(triphenylphosphine)rhodium(I) in toluene solution23,24 and by reaction of preformed chlorotris(triphenylphosphine)-rhodium(I) with hydrazine and hydrogen in an ethanol-benzene medium containing excess triphenylphosphine.23 Other syntheses employ aluminum alkyls,25 Grignard reagents,26 sodium prop-oxide,27 and hydrogen under pressure28 as reductants. 

The procedure1,2 given below affords an efficient, one-step synthesis of hydridotetrakis(triphenylphosphine)rhodium(I) from hydrated rhodium trichloride. 

Hydridotetrakis(triphenylphosphine)rhodium(I) forms yellow microcrystals which melt at 145-147° in air and at 154—156° in a capillary sealed under nitrogen. The infrared spectrum shows a band at 2156 (m) cm.-1 attributable to v(RhH). The complex is soluble in benzene, chloroform, and dichloromethane. 

Nitrosyltris(triphenylphosphine)rhodium has previously been prepared by sodium-amalgam reduction of a mixture of rhodium nitrosyl chloride and triphenylphosphine in tetrahydrofuran.32 Preparations from hydridotetrakis(triphenylphosphine)rhodium(I) and nitric oxide,24 and from rhodium trichloride, nitric oxide, triphenylphosphine, and zinc dust have also been reported.35 The following synthesis1 is convenient and rapid. 

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