Hydridotetrakis triphenylphosphine rhodium I

Hydridotetrakis(triphenylphosphine)rhodium(I) has previously been prepared by addition of triphenylphosphine to preformed hydridotris(tri-phenylphosphine)rhodium(I) in toluene solution and by reaction of preformed chlorotris(triphenylphosphine)rhodium(I) with hydrazine and hydrogen in an ethanol-benzene medium containing excess triphenylphos-phine. Other syntheses employ aluminum alkyls, Grignard reagents, sodium propoxide, and hydrogen under pressure as reductants. 

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

Present address Department of Chemistry, West Chester University, West Chester, PA (N. A.) International Nickel, Bashley Road, London N.W. 10 (J. i. L.). t Central Research Department. E. L du Pont de Nemours Company, Wilmington. 

Hot solutions of rhodium trichloride 3-hydrate (0.26 g, 1.0 mmol) in ethanol (20 mL) and potassium hydroxide (0.4 g) in ethanol (20 mL) are added rapidly and successively to a vigorously stirred, boiling solution of triphenylphos-phine (2.62 g, 10 mmol) in ethanol (80 mL). The mixture is heated under reflux for 10 min, and allowed to cool to 30°. The precipitated product is filtered washed with ethanol, water, ethanol, and n-hexane and dried in vacuo. Yield 1.10 g, (97% based on RhCla H O). 

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

---

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... 

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. 

---