TY - JOUR
T1 - Metal-silicon bonding energetics in organo-Group 4 and organo-f-element complexes. Implications for bonding and reactivity
AU - King, Wayne A.
AU - Marks, Tobin J.
N1 - Funding Information:
We thank NSF for generous support of this research under Grant CHE9104112. We thank Professor D.H. Berry for information in advance of publication.
PY - 1995/2
Y1 - 1995/2
N2 - 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.
AB - 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.
KW - Block f-element complexes
KW - Bond enthalpies
KW - Group 4 transition element complexes
KW - Organyl complexes
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U2 - 10.1016/0020-1693(94)04265-W
DO - 10.1016/0020-1693(94)04265-W
M3 - Article
AN - SCOPUS:0001179727
VL - 229
SP - 343
EP - 354
JO - Inorganica Chimica Acta
JF - Inorganica Chimica Acta
SN - 0020-1693
IS - 1-2
ER -