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 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 ((MeSiHO)₄), copolymers of dimethylsiloxane and methylhydrosiloxane, and trimethylsilyl terminated materials.

Polymethylhydrosiloxane

Names
Other names Methyl hydrogen siloxane; Poly(methyl siloxane); Poly(methylhydrosiloxane); Polysilicone 4
Identifiers
CAS Number	9004-73-3 Y
Abbreviations	PMHS
ChemSpider	none
ECHA InfoCard	100.119.568
CompTox Dashboard (EPA)	DTXSID8047501
Properties
Chemical formula	[CH3(H)SiO]n
Molar mass	variable
Density	1.006 g/cm3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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−H 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:^[3]

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