What is "polymethylhydrosiloxane"

Polymethylhydrosiloxane (PMHS) is a polymer with the general structure -(CH(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)), copolymers of dimethysiloxane and methylhydrosiloxane, and trimethylsilyl terminated materials.

This material is prepared by the hydrolysis of methyldichlorosilane:

n MeSiHCl + n HO → (MeSiHO) + 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)" + (BuSn)O → "(MeSiO" + 2 BuSnH