Acetato hydridotris triphenylphosphine ruthenium II

Bis[( + )-[(2,2-dimethyl-l,3-dioxolane-4,5-diyl)bis(methylene)]bis[diphenyl-phosphine]]hydridorhodium(l) 

Submitted by A. FENSTER, B. R. JAMES, and W. R. CULLEN Checked by R. LINCOLN and G. WILKINSONt 

The homogeneous catalyst has been prepared in alcoholic media and is a cation formed by loss of chloride. The procedure is described here for production of the neutral hydrido species HRh[( + )-diop]2, which is a slower catalyst than the in situ species for asymmetric hydrogenation but is equally effective in terms of optical yields. The method follows that of Levison and Robinson6 for synthesis of hydrido(triphenylphosphine)rhodium complexes. 

The solvated and unsolvated rhodium diop complexes are air-stable, yellow, crystalline solids solutions of the complexes, however, rapidly decompose on exposure to air. HRh[( + )-diop]2 is soluble in benzene, toluene, and dichloromethane it is slightly soluble in petroleum ether and n-hexane, and insoluble in ethanol. 

The infrared spectrum (KBr) shows an absorption in the hydride region at 2040 cm-1. The H nmr spectrum in benzene at 20° shows the Rh—H resonance as a doublet of quintets centered around t28.4. The same nmr pattern has been reported7 for HRh(CH3PPh2)4 and was attributed to a tetragonal pyramid structure, although this has been questioned.8 

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The reaction of aqueous tetrafluoroboric acid with a methanolic suspension of (acetato)hydridotris(triphenylphosphine)ruthenium(II) leads to the precipitation of hydridotris(triphenylphosphine)ruthenium(II) cation as the fluoroborate salt.1 The cation has also been produced by the decomposition of the [RuH(P(C6H5)3)4]+ cation in dichloromethane solution.2 On the basis of proton magnetic spectra, a structure with one of the phenyl rings of one triphenylphosphine bound as an arene to the metal was proposed.2 This structure has been confirmed by both x-ray diffraction and 31P nmr spectra.1... 

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