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A DFT study of SiH(4) activation by Cp(2)LnH
Lionel Perrin1, Laurent Maron, Odile Eisenstein
1Laboratoire de Structure et Dynamique des Systèmes Moléculaires et Solides (UMR 5636), Université Montpellier II, 34095 Montpellier Cedex 05, France.
Inorganic Chemistry
|August 20, 2002
Summary
Lanthanide complexes activate silane (SiH4) through sigma-bond metathesis. While H/H exchange is kinetically favored, silylation is thermodynamically preferred, differing significantly from methane activation due to silicon
Area of Science:
- Organometallic Chemistry
- Computational Chemistry
- Lanthanide Chemistry
Background:
- Lanthanide complexes are explored for catalytic applications.
- Silane activation is crucial for silicon-based chemistry.
- Understanding reaction mechanisms aids catalyst design.
Purpose of the Study:
- Investigate silane (SiH4) activation by lanthanide complexes (Cp2LnH).
- Determine reaction pathways and energy barriers for H/H exchange and silylation.
- Compare reactivity with methane activation.
Main Methods:
- Density Functional Theory (DFT) calculations using the B3PW91 functional.
- Theoretical study of the entire lanthanide series.
- Computation of reaction paths and activation barriers.
Main Results:
- Both H/H exchange and silylation proceed via a single-step sigma-bond metathesis mechanism.
- Activation barriers for H/H exchange (1.8 kcal/mol) and silylation (5.2 kcal/mol) are thermally accessible.
- Silylation is thermodynamically favored, while H/H exchange is kinetically favored.
- Reactivity differs significantly from methane activation, attributed to silicon's hypervalency.
Conclusions:
- Lanthanide complexes efficiently activate silane via sigma-bond metathesis.
- The choice between H/H exchange and silylation depends on kinetic vs. thermodynamic control.
- The enhanced reactivity towards silane compared to methane highlights the role of hypervalency in organometallic catalysis.