Polymethylhydrosiloxane

Polymethylhydrosiloxane (PMHS) is a polymer with the general structure [\sCH3(H)Si\sO\s]. 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. 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 ((MeSiHO)4), copolymers of dimethylsiloxane and methylhydrosiloxane, and trimethylsilyl terminated materials.

This material is prepared by the hydrolysis of monomethyldichlorosilane CAS#: 75-54-7:
 * n MeSiHCl2 + n H2O -> [MeSiHO]_{n} + 2n HCl

The related polymer polydimethylsiloxane (PDMS) is made similarly, but lacking Si\sH 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:


 * 2 MeSiH + (Bu3Sn)2O -> Me2Si2O + 2 Bu3SnH