C–H bond activation through steric crowding of normally inert ligands in the sterically crowded gadolinium and yttrium (C 5 Me 5 ) 3 M complexes
- 22 August 2006
- journal article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 103 (34), 12678-12683
- https://doi.org/10.1073/pnas.0602672103
Abstract
Synthesis of the sterically crowded Tris(pentamethylcyclopentadienyl) lanthanide complexes, (C5Me5)3Ln, has demonstrated that organometallic complexes with unconventionally long metal ligand bond lengths can be isolated that provide options to develop new types of ligand reactivity based on steric crowding. Previously, the (C5Me5)3M complexes were known only with the larger lanthanides, La-Sm. The synthesis of even more crowded complexes of the smaller metals Gd and Y is reported here. These complexes allow an evaluation of the size/reactivity correlations previously limited to the larger metals and demonstrate a previously undescribed type of C5Me5-based reaction, namely C-H bond activation. (C5Me5)3Gd, was prepared from GdCl3 through (C5Me5)2GdCl2K(THF)2, (C5Me5)2Gd(C3H5), and [(C5Me5)2Gd][BPh4] and structurally characterized by x-ray crystallography. Although Gd3+ is redox-inactive, (C5Me5)3Gd functions as a reducing agent in reactions with 1,3,5,7-cyclooctatetraene (COT) and triphenylphosphine selenide to make (C5Me5)Gd(C8H8), [(C5Me5)2Gd]2Se2, and [(C5Me5)2Gd]2Se depending on the stoichiometry used. When the analogous synthetic method was attempted with yttrium in arene solvents, the previously characterized (C5Me5)2YR complexes (R=C6H5, CH2C6H5) were isolated instead, i.e., C-H bond activation of solvent occurred. To avoid this problem, (C5Me5)3Y was synthesized in high yield from [(C5Me5)2YH]2 and tetramethylfulvene in aliphatic solvents. Isolated (C5Me5)3Y was found to metalate benzene and toluene with concomitant formation of C5Me5H, a reaction contrary to the normal pKa values of these hydrocarbons. In this case, the normally inert (C5Me5)1- ligand engages in C-H bond activation due to the extreme steric crowding.Keywords
This publication has 36 references indexed in Scilit:
- Features of organolanthanide complexesPublished by Springer Science and Business Media LLC ,2005
- Early developments in lanthanide-based dinitrogen reduction chemistryCanadian Journal of Chemistry, 2005
- Chemistry of Tris(pentamethylcyclopentadienyl) f-Element Complexes, (C5Me5)3MChemical Reviews, 2002
- Activity of [Sm(C5Me5)3] in Ethylene Polymerization and Synthesis of [U (C5Me5)3], the First Tris(pentamethylcyclopentadienyl) 5f‐Element ComplexAngewandte Chemie-International Edition, 1997
- Carbon-hydrogen activation of arenes and substituted arenes by the yttrium hydride (Cp*2YH)2: competition between Cp* ligand metalation, arene metalation, and hydrogen/deuterium exchange. Molecular structures of Cp*2Y(.mu.-H)(.mu.-.eta.1,.eta.5-CH2C5Me4)YCp* and Cp*2Y(o-C6H4PPh2CH2)Organometallics, 1993
- Ein einfacher Weg zu 1,2,3,4-Tetramethylfulven und zu 1-funktionalisierten 2,3,4,5-TetramethylcyclopentadienenSynthesis, 1992
- Organo-f-element thermochemistry. Absolute metal-ligand bond disruption enthalpies in bis(pentamethylcyclopentadienyl)samarium hydrocarbyl, hydride, dialkylamide, alkoxide, halide, thiolate, and phosphide complexes. Implications for organolanthanide bonding and reactivityJournal of the American Chemical Society, 1989
- Electron-transfer reactions of divalent ytterbium metallocenes. Synthesis of the series [(Me5C5)2Yb]2[.mu.-E] (E = oxygen, sulfur, selenium, or tellurium) and crystal structure of [(Me5C5)2Yb]2[.mu.-Se]Organometallics, 1989
- Reactions of yttrium-carbon bonds with active hydrogen-containing molecules. A useful synthetic method for permethylyttrocene derivativesOrganometallics, 1987
- Mono-η-cycloheptatrienyltitanium chemistry: synthesis, molecular and electronic structures, and reactivity of the complexes [Ti(η-C7H7)L2X](L = tertiary phosphine, O- or N-donor ligand; X = Cl or alkyl)J. Chem. Soc., Dalton Trans., 1985