Polymethylhydrosiloxane

Polymethylhydrosiloxane
Other names Methyl hydrogen siloxane; Poly(methyl siloxane); Poly(methylhydrosiloxane); Polysilicone 4
Identifiers
Abbreviations	PMHS
CAS number	9004-73-3 Y
	Properties
Molecular formula	(CH3(H)SiO)n
Molar mass	variable
Density	1.06 g/cm3
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

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.^[1] 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, and 63148-57-2. 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 → (MeSiH)_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]

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

References

1. ↑ J. M. Lavis, R. E. Maleczka, Jr. "Polymethylhydrosiloxane" Encyclopedia of Reagents for Organic Synthesis 2003, John Wiley & Sons. doi:10.1002/047084289X.rn00062
2. ↑ Jordi Tormo and Gregory C. Fu (2002), "Tributylstannane (Bu₃SnH)-Catalyzed Barton-McCombie deoxygenation of Alcohols: 3-Deoxy-1,2:5,6-bis-O-(1-methylethyilidine)-α-D-ribo-hexafuranose", Org. Synth. 78: 239