polymethylhydrosiloxane

{{short description|Organic polymer with the repeating formula [CH3(H)SiO]}}

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|verifiedrevid = 464209986

|ImageFile = Polymethylhydrosiloxane.png

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|OtherNames = Methyl hydrogen siloxane; Poly(methyl siloxane); Poly(methylhydrosiloxane); Polysilicone 4

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|Abbreviations = PMHS

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|CASNo = 9004-73-3

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|Section2={{Chembox Properties

|Formula = {{chem2|[CH3(H)SiO]_{n} }}

|MolarMass = variable

|Density = 1.006 g/cm³

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Polymethylhydrosiloxane (PMHS) is a polymer with the general structure {{chem2|[\sCH3(H)Si\sO\s]}}. 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.J. M. Lavis, R. E. Maleczka, Jr. "Polymethylhydrosiloxane" Encyclopedia of Reagents for Organic Synthesis 2003, John Wiley & Sons {{doi|10.1002/047084289X.rn00062}}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}} 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 ({{chem2|(MeSiHO)4}}), copolymers of dimethylsiloxane and methylhydrosiloxane, and trimethylsilyl terminated materials.

This material is prepared by the hydrolysis of monomethyldichlorosilane CAS#: 75-54-7:

:{{chem2|n MeSiHCl2 + n H2O -> [MeSiHO]_{n} + 2n HCl}}

The related polymer polydimethylsiloxane (PDMS) is made similarly, but lacking {{chem2|Si\sH}} 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:{{OrgSynth| author=Jordi Tormo and Gregory C. Fu| year=2002| title=Tributylstannane (Bu₃SnH)-Catalyzed Barton-McCombie deoxygenation of Alcohols: 3-Deoxy-1,2:5,6-bis-O-(1-methylethyilidine)-α-D-ribo-hexafuranose| volume=78| pages=239}}

: {{chem2|2 MeSiH + (Bu3Sn)2O -> Me2Si2O + 2 Bu3SnH}}