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Catalytic activity of iridium siloxide complexes in cross-linking of silicones by hydrosilylation ☆

Paper ID Volume ID Publish Year Pages File Format Full-Text
44454 46030 2007 5 PDF Available
Title
Catalytic activity of iridium siloxide complexes in cross-linking of silicones by hydrosilylation ☆
Abstract

A series of catalytic examinations have shown that monomeric iridium siloxides ([Ir(cod)(PCy3)(OSiMe3)] (II), [Ir(CO)(PPh3)2(OSiMe3)] (III) and [Ir(CO)(PCy3)2(OSiMe3)] (IV)) are effective catalysts for model homogeneous hydrosilylation of vinyltris(trimethylsiloxy)silane as well as cross-linking of commercial polysiloxane system. The results of stoichiometric reactions of iridium siloxide with heptamethyltrisiloxane and observed catalytic properties are consistent with the mechanism of catalysis involving a generation of the key-intermediate (16e tetracoordinate Ir–H complex) responsible for the catalytic cycle. Experiments allowed explaining the effect of oxygen on the catalytic activity of phosphine-containing iridium siloxide complexes. The curing process of polysiloxanes catalyzed by iridium siloxide II and IV complexes occurs at a higher temperature (about 200 °C) than the same system catalyzed by Karstedt—diallylmaleate system (130 °C). The enthalpies of the reaction are comparable (−30 to −38 kJ/mol) for both catalysts but the inhibitor is not required for the iridium-catalyzed process.

Graphical abstractA series of catalytic examinations show that monomeric iridium siloxides ([Ir(cod)(PCy3)(OSiMe3)] (II), [Ir(CO)(PPh3)2(OSiMe3)] (III) and [Ir(CO)(PCy3)2(OSiMe3)] (IV)) are effective and selective catalysts for model homogeneous hydrosilylation of vinyltrisiloxane as well as cross-linking of commercial polysiloxane system. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Silicones; Cross-linking; Hydrosilylation; Iridium complexes
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Catalytic activity of iridium siloxide complexes in cross-linking of silicones by hydrosilylation ☆
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 317, Issue 1, 27 January 2007, Pages 53–57
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Price was $35.95
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Price after discount Only $4.95
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