PHENYLSILANE

Organosilanes are hydrocarbon-like and possess the ability to serve as both ionic and free-radical reducing agents. These reagents and their reaction by-products are safer and more easily handled and disposed than many other reducing agents. The metallic nature of silicon and its low electronegativity relative to hydrogen lead to polarization of the Si-H bond yielding a hydridic hydrogen and a milder reducing agent compared to aluminum-, boron-, and other metal-based hydrides. A summary of some key silane reductions are presented in Table 1 of the Silicon-Based Reducing Agents brochure.

Silyl Hydrides are a distinct class of silanes that behave and react very differently than conventional silane coupling agents. They react with the liberation of byproduct hydrogen. Silyl hydrides can react with hydroxylic surfaces under both non-catalyzed and catalyzed conditions by a dehydrogenative coupling mechanism. Trihydridosilanes react with a variety of pure metal surfaces including gold, titanium, zirconium and amorphous silicon, by a dissociative adsorption mechanism. The reactions generally take place at room temperature and can be conducted in the vapor phase or with the pure silane or solutions of the silane in aprotic solvents. Deposition should not be conducted in water, alcohol or protic solvents.

ΔH_vap: 34.8 kJ/mol

Employed in the reduction of esters to ethers

Reduces α,β-unsaturated ketones to saturated ketones in the presence of tri-n-butyltin hydride

Reduces tin amides to tin hydrides

Used in the tin-catalyzed reduction of nitroalkanes to alkanes

Reduces α-halo ketones in presence of Mo(0)

Adds to norbornene with high ee

Reducing reagent in radical reductions

Yields ISiH₃ on treatments with HI in presence of AlI₃

Extensive review of silicon based reducing agents: Larson, G.; Fry, J. L. "Ionic and Organometallic-Catalyzed Organosilane Reductions", Wipf, P., Ed.; Wiley, 2007