C2-Symmetric ansa-lanthanidocene complexes. Synthesis via silylamine elimination and β-SiH agostic rigidity

Jörg Eppinger; Michael Spiegler; Wolfgang Hieringer; Wolfgang A. Herrmann; Reiner Anwander

doi:10.1021/ja992786a

C₂-Symmetric ansa-lanthanidocene complexes. Synthesis via silylamine elimination and β-SiH agostic rigidity

Jörg Eppinger, Michael Spiegler, Wolfgang Hieringer, Wolfgang A. Herrmann, Reiner Anwander^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

189 Scopus citations

Abstract

The synthesis as well as the spectroscopic and structural characterization of a new class of C₂-symmetric, mononuclear metallocene complexes of the lanthanide elements is described. Heteroleptic lanthanidocene silylamide complexes have been obtained ate-complex-free according to silylamine elimination reactions of complexes Ln[N(SiHMe₂)₂]₃(THF)(x) (x = 1, Ln = Sc; x = 2, Ln = Y, La, Nd, Lu) and linked, substituted cyclopentadiene and indene systems. The molecular structure of [Me₂Si(C₅Me₄)₂]La[N(SiHMe₂)₂] (95% isolated yield) has been determined by X-ray crystallography. Brintzinger-type, indenyl-derived metallocene complexes have been isolated in racemic yields as high as 72%. IR and multinuclear NMR spectroscopy (¹H, ¹³C, ²⁹Si, ⁸⁹Y) reveals the presence of an unprecedented strong diagnostic interaction between the electron-deficient metal centers and the SiH moiety of the bis(dimethylsilyl)amide ligand: SiH stretching vibrations as low as 1759 cm^- ¹ and ¹J(Si,H) coupling constants as low as 133 Hz indicate a distinct weakening of the SiH bonding. X-ray structure analyses of the compounds rac- [Me₂Si(2-Me-Benz-Ind)₂]Ln[N(SiHMe₂)₂] (Ln = Y, Lu) and rac-[Me₂Si(2-Me- C₉H₅)₂]Ln[N(SiHMe₂)₂] (Ln = Y, Lu) show that the structural features of both the chelating ancillary ligands and such agostically fused metallacycles depend on the type of the ligand and the size of the metal: bite angles Ω of approximately 'U-shaped' ansa-ligands as large as 68.2(2)°and Ln-Si and Ln- H contacts as close as 3.028(1) and 2.37(3) Å, respectively, have been detected, the latter forcing very large Si-N-Si angles up to 160.1(2)°. The isolation of reaction intermediates such as Y[N(SiHMe₂)₂]₃(THF) and partly exchanged [Me₂Si(2-Me-4-Ph-Ind)₂H]Y[N(SiHMe₂)₂]₂ provides mechanistic details of this peculiar silylamine elimination reaction. Additionally, the pK(a) values of various protonated ligands including new 9-(SiHMe₂)- fluorene, 3-(SiHMe₂)-indene, and 3-(SiHMe₂)-2-Me-indene determined according to the method of Fraser give evidence of a thermodynamically controlled ligand exchange.

Original language	English (US)
Pages (from-to)	3080-3096
Number of pages	17
Journal	Journal of the American Chemical Society
Volume	122
Issue number	13
DOIs	https://doi.org/10.1021/ja992786a
State	Published - Apr 5 2000
Externally published	Yes

ASJC Scopus subject areas

Catalysis
General Chemistry
Biochemistry
Colloid and Surface Chemistry

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10.1021/ja992786a

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@article{84d63488cb834ed5a301d971cac3fc3d,

title = "C2-Symmetric ansa-lanthanidocene complexes. Synthesis via silylamine elimination and β-SiH agostic rigidity",

abstract = "The synthesis as well as the spectroscopic and structural characterization of a new class of C2-symmetric, mononuclear metallocene complexes of the lanthanide elements is described. Heteroleptic lanthanidocene silylamide complexes have been obtained ate-complex-free according to silylamine elimination reactions of complexes Ln[N(SiHMe2)2]3(THF)(x) (x = 1, Ln = Sc; x = 2, Ln = Y, La, Nd, Lu) and linked, substituted cyclopentadiene and indene systems. The molecular structure of [Me2Si(C5Me4)2]La[N(SiHMe2)2] (95% isolated yield) has been determined by X-ray crystallography. Brintzinger-type, indenyl-derived metallocene complexes have been isolated in racemic yields as high as 72%. IR and multinuclear NMR spectroscopy (1H, 13C, 29Si, 89Y) reveals the presence of an unprecedented strong diagnostic interaction between the electron-deficient metal centers and the SiH moiety of the bis(dimethylsilyl)amide ligand: SiH stretching vibrations as low as 1759 cm- 1 and 1J(Si,H) coupling constants as low as 133 Hz indicate a distinct weakening of the SiH bonding. X-ray structure analyses of the compounds rac- [Me2Si(2-Me-Benz-Ind)2]Ln[N(SiHMe2)2] (Ln = Y, Lu) and rac-[Me2Si(2-Me- C9H5)2]Ln[N(SiHMe2)2] (Ln = Y, Lu) show that the structural features of both the chelating ancillary ligands and such agostically fused metallacycles depend on the type of the ligand and the size of the metal: bite angles Ω of approximately 'U-shaped' ansa-ligands as large as 68.2(2)°and Ln-Si and Ln- H contacts as close as 3.028(1) and 2.37(3) {\AA}, respectively, have been detected, the latter forcing very large Si-N-Si angles up to 160.1(2)°. The isolation of reaction intermediates such as Y[N(SiHMe2)2]3(THF) and partly exchanged [Me2Si(2-Me-4-Ph-Ind)2H]Y[N(SiHMe2)2]2 provides mechanistic details of this peculiar silylamine elimination reaction. Additionally, the pK(a) values of various protonated ligands including new 9-(SiHMe2)- fluorene, 3-(SiHMe2)-indene, and 3-(SiHMe2)-2-Me-indene determined according to the method of Fraser give evidence of a thermodynamically controlled ligand exchange.",

author = "J{\"o}rg Eppinger and Michael Spiegler and Wolfgang Hieringer and Herrmann, {Wolfgang A.} and Reiner Anwander",

year = "2000",

month = apr,

day = "5",

doi = "10.1021/ja992786a",

language = "English (US)",

volume = "122",

pages = "3080--3096",

journal = "Journal of the American Chemical Society",

issn = "0002-7863",

publisher = "American Chemical Society",

number = "13",

}

TY - JOUR

T1 - C2-Symmetric ansa-lanthanidocene complexes. Synthesis via silylamine elimination and β-SiH agostic rigidity

AU - Eppinger, Jörg

AU - Spiegler, Michael

AU - Hieringer, Wolfgang

AU - Herrmann, Wolfgang A.

AU - Anwander, Reiner

PY - 2000/4/5

Y1 - 2000/4/5

N2 - The synthesis as well as the spectroscopic and structural characterization of a new class of C2-symmetric, mononuclear metallocene complexes of the lanthanide elements is described. Heteroleptic lanthanidocene silylamide complexes have been obtained ate-complex-free according to silylamine elimination reactions of complexes Ln[N(SiHMe2)2]3(THF)(x) (x = 1, Ln = Sc; x = 2, Ln = Y, La, Nd, Lu) and linked, substituted cyclopentadiene and indene systems. The molecular structure of [Me2Si(C5Me4)2]La[N(SiHMe2)2] (95% isolated yield) has been determined by X-ray crystallography. Brintzinger-type, indenyl-derived metallocene complexes have been isolated in racemic yields as high as 72%. IR and multinuclear NMR spectroscopy (1H, 13C, 29Si, 89Y) reveals the presence of an unprecedented strong diagnostic interaction between the electron-deficient metal centers and the SiH moiety of the bis(dimethylsilyl)amide ligand: SiH stretching vibrations as low as 1759 cm- 1 and 1J(Si,H) coupling constants as low as 133 Hz indicate a distinct weakening of the SiH bonding. X-ray structure analyses of the compounds rac- [Me2Si(2-Me-Benz-Ind)2]Ln[N(SiHMe2)2] (Ln = Y, Lu) and rac-[Me2Si(2-Me- C9H5)2]Ln[N(SiHMe2)2] (Ln = Y, Lu) show that the structural features of both the chelating ancillary ligands and such agostically fused metallacycles depend on the type of the ligand and the size of the metal: bite angles Ω of approximately 'U-shaped' ansa-ligands as large as 68.2(2)°and Ln-Si and Ln- H contacts as close as 3.028(1) and 2.37(3) Å, respectively, have been detected, the latter forcing very large Si-N-Si angles up to 160.1(2)°. The isolation of reaction intermediates such as Y[N(SiHMe2)2]3(THF) and partly exchanged [Me2Si(2-Me-4-Ph-Ind)2H]Y[N(SiHMe2)2]2 provides mechanistic details of this peculiar silylamine elimination reaction. Additionally, the pK(a) values of various protonated ligands including new 9-(SiHMe2)- fluorene, 3-(SiHMe2)-indene, and 3-(SiHMe2)-2-Me-indene determined according to the method of Fraser give evidence of a thermodynamically controlled ligand exchange.

AB - The synthesis as well as the spectroscopic and structural characterization of a new class of C2-symmetric, mononuclear metallocene complexes of the lanthanide elements is described. Heteroleptic lanthanidocene silylamide complexes have been obtained ate-complex-free according to silylamine elimination reactions of complexes Ln[N(SiHMe2)2]3(THF)(x) (x = 1, Ln = Sc; x = 2, Ln = Y, La, Nd, Lu) and linked, substituted cyclopentadiene and indene systems. The molecular structure of [Me2Si(C5Me4)2]La[N(SiHMe2)2] (95% isolated yield) has been determined by X-ray crystallography. Brintzinger-type, indenyl-derived metallocene complexes have been isolated in racemic yields as high as 72%. IR and multinuclear NMR spectroscopy (1H, 13C, 29Si, 89Y) reveals the presence of an unprecedented strong diagnostic interaction between the electron-deficient metal centers and the SiH moiety of the bis(dimethylsilyl)amide ligand: SiH stretching vibrations as low as 1759 cm- 1 and 1J(Si,H) coupling constants as low as 133 Hz indicate a distinct weakening of the SiH bonding. X-ray structure analyses of the compounds rac- [Me2Si(2-Me-Benz-Ind)2]Ln[N(SiHMe2)2] (Ln = Y, Lu) and rac-[Me2Si(2-Me- C9H5)2]Ln[N(SiHMe2)2] (Ln = Y, Lu) show that the structural features of both the chelating ancillary ligands and such agostically fused metallacycles depend on the type of the ligand and the size of the metal: bite angles Ω of approximately 'U-shaped' ansa-ligands as large as 68.2(2)°and Ln-Si and Ln- H contacts as close as 3.028(1) and 2.37(3) Å, respectively, have been detected, the latter forcing very large Si-N-Si angles up to 160.1(2)°. The isolation of reaction intermediates such as Y[N(SiHMe2)2]3(THF) and partly exchanged [Me2Si(2-Me-4-Ph-Ind)2H]Y[N(SiHMe2)2]2 provides mechanistic details of this peculiar silylamine elimination reaction. Additionally, the pK(a) values of various protonated ligands including new 9-(SiHMe2)- fluorene, 3-(SiHMe2)-indene, and 3-(SiHMe2)-2-Me-indene determined according to the method of Fraser give evidence of a thermodynamically controlled ligand exchange.

UR - http://www.scopus.com/inward/record.url?scp=0034607379&partnerID=8YFLogxK

U2 - 10.1021/ja992786a

DO - 10.1021/ja992786a

M3 - Article

AN - SCOPUS:0034607379

SN - 0002-7863

VL - 122

SP - 3080

EP - 3096

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 13

ER -

C₂-Symmetric ansa-lanthanidocene complexes. Synthesis via silylamine elimination and β-SiH agostic rigidity

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