de.mpg.escidoc.pubman.appbase.FacesBean
English
 
Help Guide Privacy Policy Disclaimer Contact us
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT

Released

Journal Article

Hydrosilylation with bis(alkynyl)(1,5-cyclooctadiene) platinum catalysts: A density functional study of the initial activation

MPS-Authors
http://pubman.mpdl.mpg.de/cone/persons/resource/persons58639

Jagadeesh,  M. N.
Research Department Thiel, Max-Planck-Institut für Kohlenforschung, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons59045

Thiel,  W.
Research Department Thiel, Max-Planck-Institut für Kohlenforschung, Max Planck Society;
Research Department Thiel, Max-Planck-Institut für Kohlenforschung, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons58707

Köhler,  J.
Research Department Thiel, Max-Planck-Institut für Kohlenforschung, Max Planck Society;

Locator
There are no locators available
Fulltext (public)
There are no public fulltexts available
Supplementary Material (public)
There is no public supplementary material available
Citation

Jagadeesh, M. N., Thiel, W., Köhler, J., & Fehn, A. (2002). Hydrosilylation with bis(alkynyl)(1,5-cyclooctadiene) platinum catalysts: A density functional study of the initial activation. Organometallics, 21(10), 2076-2087. doi:10.1021/om0200196.


Cite as: http://hdl.handle.net/11858/00-001M-0000-000F-99E5-A
Abstract
At elevated temperatures bis(alkynyl)(1,5- cyclooctadiene)platinum complexes catalyze the cross-linking of polyorganosiloxanes containing Si-H and vinyl groups. Density functional calculations with medium-size basis sets and effective core potentials are reported for reactions that may activate these precatalysts for hydrosilylation. For a model system consisting of the bis(ethynyl) complex, trimethylsilane, and ethylene, the computations provide two plausible pathways for gaining access to the Chalk-Harrod cycle. The first one involves a sequence of four oxidative additions and reductive eliminations, while the second one requires a reductive coupling that is induced by olefin coordination. In both cases, the initial step is rate-determining, with a computed barrier of 27 kcal/mol. Experiments for polysiloxane systems of industrial interest favor the first pathway and yield barriers of 25-30 kcal/mol. Substituents in the alkynyl groups affect the measured barriers and the barriers computed for the rate- determining initial step of the first pathway in a qualitatively similar manner. We propose that the activation of the precatalysts is initiated by oxidative addition of Si-H.