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Poly(methylhydrosiloxane): Overview and Conversion Method of its Waste to Useful Commodities

Nov 5,2024

Poly(methylhydrosiloxane) (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.

Poly(methylhydrosiloxane)

Preparation

Poly(methylhydrosiloxane) is prepared by the hydrolysis of monomethyldichlorosilane:

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 is then used instead of monomethyldichlorosilane.

Illustrative of its use, PMHS is used for in situ conversion of tributyltin oxide to tributyltin hydride:

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

Uses

Poly(methylhydrosiloxane) (PMHS) is an easily han dled, inexpensive, non-toxic, and mild reducing agent. Although relatively inert towards organic functionality, PMHS can transfer its hydride to a variety of metalcatalysts (including Sn, Ti, Zn, Cu, and Pd) which can then participate in a wide range of reductions. Alternatively, when made hypercoordinate by the action of fluo ride or other nucleophiles, PMHS can act directly as a reducing agent. PMHS is attractive as a substitute for more expensive or hazardous silanes or siloxanes and as the stoichiometric reductant in catalytic organotin-mediated processes.1

References:

[1] Aldrichimica ACTA[J]. C&EN Global Enterprise, 2009, 87 48: 1-40. DOI:10.1021/cen-v087n048.p002.

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