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Other names
Methyl hydrogen siloxane; Poly(methyl siloxane); Poly(methylhydrosiloxane); Polysilicone 4
Abbreviations PMHS
  • none
ECHA InfoCard 100.119.568
Molar mass variable
Density 1.06 g/cm3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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. These include the tetramer ((MeSiHO)4), copolymers of dimethylsiloxane 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]

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


  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. 

Further reading[edit]

  • Larson, G. L.; Fry, J. L., "Ionic and organometallic-catalyzed organosilane reductions", Organic Reactions 2008, 71, 1-737. doi:10.1002/0471264180.or071.01