Abstract
Metal-silicon bond disruption enthalpies have been measured for a series of U, Zr, and Sm metallocene complexes: Cp3USi(TMS)3, Cp2Zr(Cl)Si(TMS)3, Cp2Zr(Me)Si(TMS)3, Cp2Zr(TMS)Si(TMS)3, Cp2Zr(TMS)OtBu, Cp′2SmSiH(TMS)2 (Cp = η5-C5H5, Cp′ = η5-Me5C5, TMS = trimethylsilyl). Data were obtained by anaerobic batch-titration solution calorimetry in toluene. Derived metal-ligand bond enthalpies D(LnM-R) in kcal mol-1 are: D[Cp3USi(TMS)3] = 37(3), D[Cp2(Cl)ZrSi(TMS)3]=57(3), D[Cp2(Me)ZrSi(TMS)3]=56(5), D[Cp2(Si(TMS)3)ZrMe] = 66(5), D[Cp2(OtBu)Zr-TMS] = 60(5), D[Cp2(TMS)ZrSi(TMS)3] = 42(11), D[Cp2(Si(TMS)3)Zr-TMS] = 45(7), D[Cp′2SmSiH(TMS)2] = 43(5). These results show that metal-silicon bond disruption enthalpies involving these electron-deficient metals are substantially smaller than those of the corresponding metal hydride and hydrocarbyl bonds. These data in combination with previously measured metal-ligand bond enthalpies allow thermodynamic analyses of a variety of stoichiometric and catalytic transformations involving metal silyl functionalities. The latter include potential pathways for dehydrogenative silane polymerization, dehydrogenative silane-hydrocarbon coupling, olefin hydrosilylation, and dehydrogenative silane-amine coupling. It is not uncommon for there to be multiple pathways which effect the same catalytic transformation and which contain no steps having major enthalpic impediments.
Original language | English (US) |
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Pages (from-to) | 343-354 |
Number of pages | 12 |
Journal | Inorganica Chimica Acta |
Volume | 229 |
Issue number | 1-2 |
DOIs | |
State | Published - Feb 1995 |
Keywords
- Block f-element complexes
- Bond enthalpies
- Group 4 transition element complexes
- Organyl complexes
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry