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Polymethylhydrosiloxane

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Organic polymer with the repeating formula
Polymethylhydrosiloxane
Names
Other names Methyl hydrogen siloxane; Poly(methyl siloxane); Poly(methylhydrosiloxane); Polysilicone 4
Identifiers
CAS Number
Abbreviations PMHS
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Properties
Chemical formula [CH3(H)SiO]n
Molar mass variable
Density 1.006 g/cm
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). ☒N verify (what is  ?) Infobox references
Chemical compound

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. 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 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:

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. Revunova, K., & Nikonov, G. I. (2014). Base-Catalyzed Hydrosilylation of Ketones and Esters and Insight into the Mechanism. Chemistry-a European Journal, 20(3), 839-845. doi:10.1002/chem.201302728
  3. 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". Organic Syntheses. 78: 239.

Further reading

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