Polymethylhydrosiloxane

Polymethylhydrosiloxane (PMHS) is a polymer with the general structure -(CH₃(H)Si-O)-. It is used in organic chemistry as a mild and stable reducing agent easily transferring hydrides to metal centers. 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 dimethysiloxane and methylhydrosiloxane, and trimethylsilyl terminated materials.

This material is prepared by the hydrolysis of methyldichlorosilane:

n MeSiHCl₂ + n H₂O → (MeSiHO)_n + 2n HCl

The related polymer polydimethylsiloxane (PDMS) is made similarly, but lacking Si-H bonds, it exhibits no reducing properties.

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

2"(MeSiH)" + (Bu₃Sn)₂O → "(Me₂Si₂O" + 2 Bu₃SnH