Ancillary ligand effects on organo-f-element reactivity. ansa-metallocenes with bridge-tethered donors

Peter W. Roesky; Charlotte L. Stern; Tobin J. Marks

doi:10.1021/om970483o

Ancillary ligand effects on organo-f-element reactivity. ansa-metallocenes with bridge-tethered donors

Peter W. Roesky, Charlotte L. Stern, Tobin J. Marks^*

^*Corresponding author for this work

Chemistry

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

84 Scopus citations

Abstract

The synthesis and reactivity of ansa-metallocenes based upon the new ligand system R(Me)SiCp″₂^2- (Cp″ = C₅Me₄ and R = (CH₂)_nOMe, n = 3-5) is reported. The tethered donor functionality, which is appended via varying chain lengths to the silicon bridge, is introduced to examine possible intramolecular reactivity modifications. The key step of the ligand synthesis is the hydrosilylative fusion of the donor functionality R to the silicon center. The complexes [R(Me)SiCp″₂]LnCH(SiMe₃)₂ (Ln = Y, Sm) were synthesized to investigate the influence of the tethered ether group on the reactivity and catalytic properties. Catalytic reactions in which the substrate is a relatively weak donor, such as in olefin hydrogenation, exhibit depressed turnover frequencies, presumably reflecting competition between the substrate and donor functionality for the empty coordination site at the metal center. In contrast, for amino-alkene hydroamination/cyclization in which a strong amine donor is the substrate, catalytic activity is significantly enhanced while diastereoselectivity is essentially unchanged. The molecular structure of the precatalyst [MeO(CH₂)₅(Me)SiCp″₂]-YCH(SiMC ₃)₂ has been determined by X-ray diffraction.

Original language	English (US)
Pages (from-to)	4705-4711
Number of pages	7
Journal	Organometallics
Volume	16
Issue number	21
DOIs	https://doi.org/10.1021/om970483o
State	Published - Oct 14 1997

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

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title = "Ancillary ligand effects on organo-f-element reactivity. ansa-metallocenes with bridge-tethered donors",

abstract = "The synthesis and reactivity of ansa-metallocenes based upon the new ligand system R(Me)SiCp″22- (Cp″ = C5Me4 and R = (CH2)nOMe, n = 3-5) is reported. The tethered donor functionality, which is appended via varying chain lengths to the silicon bridge, is introduced to examine possible intramolecular reactivity modifications. The key step of the ligand synthesis is the hydrosilylative fusion of the donor functionality R to the silicon center. The complexes [R(Me)SiCp″2]LnCH(SiMe3)2 (Ln = Y, Sm) were synthesized to investigate the influence of the tethered ether group on the reactivity and catalytic properties. Catalytic reactions in which the substrate is a relatively weak donor, such as in olefin hydrogenation, exhibit depressed turnover frequencies, presumably reflecting competition between the substrate and donor functionality for the empty coordination site at the metal center. In contrast, for amino-alkene hydroamination/cyclization in which a strong amine donor is the substrate, catalytic activity is significantly enhanced while diastereoselectivity is essentially unchanged. The molecular structure of the precatalyst [MeO(CH2)5(Me)SiCp″2]-YCH(SiMC 3)2 has been determined by X-ray diffraction.",

author = "Roesky, {Peter W.} and Stern, {Charlotte L.} and Marks, {Tobin J.}",

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AU - Roesky, Peter W.

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AU - Marks, Tobin J.

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N2 - The synthesis and reactivity of ansa-metallocenes based upon the new ligand system R(Me)SiCp″22- (Cp″ = C5Me4 and R = (CH2)nOMe, n = 3-5) is reported. The tethered donor functionality, which is appended via varying chain lengths to the silicon bridge, is introduced to examine possible intramolecular reactivity modifications. The key step of the ligand synthesis is the hydrosilylative fusion of the donor functionality R to the silicon center. The complexes [R(Me)SiCp″2]LnCH(SiMe3)2 (Ln = Y, Sm) were synthesized to investigate the influence of the tethered ether group on the reactivity and catalytic properties. Catalytic reactions in which the substrate is a relatively weak donor, such as in olefin hydrogenation, exhibit depressed turnover frequencies, presumably reflecting competition between the substrate and donor functionality for the empty coordination site at the metal center. In contrast, for amino-alkene hydroamination/cyclization in which a strong amine donor is the substrate, catalytic activity is significantly enhanced while diastereoselectivity is essentially unchanged. The molecular structure of the precatalyst [MeO(CH2)5(Me)SiCp″2]-YCH(SiMC 3)2 has been determined by X-ray diffraction.

AB - The synthesis and reactivity of ansa-metallocenes based upon the new ligand system R(Me)SiCp″22- (Cp″ = C5Me4 and R = (CH2)nOMe, n = 3-5) is reported. The tethered donor functionality, which is appended via varying chain lengths to the silicon bridge, is introduced to examine possible intramolecular reactivity modifications. The key step of the ligand synthesis is the hydrosilylative fusion of the donor functionality R to the silicon center. The complexes [R(Me)SiCp″2]LnCH(SiMe3)2 (Ln = Y, Sm) were synthesized to investigate the influence of the tethered ether group on the reactivity and catalytic properties. Catalytic reactions in which the substrate is a relatively weak donor, such as in olefin hydrogenation, exhibit depressed turnover frequencies, presumably reflecting competition between the substrate and donor functionality for the empty coordination site at the metal center. In contrast, for amino-alkene hydroamination/cyclization in which a strong amine donor is the substrate, catalytic activity is significantly enhanced while diastereoselectivity is essentially unchanged. The molecular structure of the precatalyst [MeO(CH2)5(Me)SiCp″2]-YCH(SiMC 3)2 has been determined by X-ray diffraction.

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Ancillary ligand effects on organo-f-element reactivity. ansa-metallocenes with bridge-tethered donors

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