[1828-36-1] · C72H61P4Rh · Hydridotetrakis(triphenylphosphine)rhodium · (MW 1153.12)
Physical Data: mp 162-163 °C.
Solubility: slightly sol benzene, toluene, THF, acetone.
Form Supplied in: yellow crystals.
Purification: by recrystallization from toluene or benzene.
Handling, Storage, and Precautions: solid material is moderately sensitive to oxygen, but in solution it is easily decomposed by air.
A number of different substituted styryl ketones have been reduced by 1-phenylethanol at 50 °C in the presence of catalytic amounts of (PPh3)4RhH (eq 1). The initial rate of reduction increases when the aromatic ring contains electron-withdrawing groups and decreases in the presence of electron-releasing substituents.
Hydrosilylation of acetylene with trichlorosilane, triethoxysilane, methyldichlorosilane, methyldiethoxysilane, and n-hexyldichlorosilane takes place in either xylene or toluene in the presence of catalytic amounts of (PPh3)4RhH (eq 2).
a-Trimethylsilyl ketones are useful compounds in the synthesis of di- and trisubstituted alkenes5 and in aldol reactions.6 The preparation of such ketones can be carried out by any of the following reactions catalyzed by (PPh3)4RhH: isomerization of b-trimethylsilyl allyl alcohols, isomerization of b´-trimethylsilyl allyl alcohols, or dehydrogenation of b-trimethylsilyl alcohols via hydrogen transfer to a,b-enones.
(E)-a,b-Unsaturated carbonyl compounds can be selectively obtained from the Rh-catalyzed isomerization of vinyl epoxides (eq 3). The starting monoepoxides can be prepared according to eq 4.7
Other applications include removal of the allyl ether protecting group in the presence of trifluoroacetic acid,8 and the synthesis of allylsilanes.9
Emory University, Atlanta, GA, USA