Polymethylhydrosiloxane Explained

Polymethylhydrosiloxane (PMHS) is a polymer with the general structure . It is used in organic chemistry as a mild and stable reducing agent easily transferring hydrides to metal centers and a number of other reducible functional groups.^{[1] [2]} A variety of related materials are available under the following CAS registry numbers 9004-73-3, 16066-09-4, 63148-57-2, 178873-19-3. These include the tetramer, copolymers of dimethylsiloxane and methylhydrosiloxane, and trimethylsilyl terminated materials.

This material is prepared by the hydrolysis of monomethyldichlorosilane CAS#: 75-54-7:

The related polymer polydimethylsiloxane (PDMS) is made similarly, but lacking bonds, it exhibits no reducing properties. Dimethyldichlorosilane CAS#: 75-78-5 is then used instead of monomethyldichlorosilane CAS#: 75-54-7.

Illustrative of its use, PMHS is used for in situ conversion of tributyltin oxide to tributyltin hydride:

References

1. J. M. Lavis, R. E. Maleczka, Jr. "Polymethylhydrosiloxane" Encyclopedia of Reagents for Organic Synthesis 2003, John Wiley & Sons
2. Revunova, K., & Nikonov, G. I. (2014). Base-Catalyzed Hydrosilylation of Ketones and Esters and Insight into the Mechanism. Chemistry-a European Journal, 20(3), 839-845.

Further reading

• Larson, G. L.; Fry, J. L., "Ionic and organometallic-catalyzed organosilane reductions", Organic Reactions 2008, 71, 1-737.