Issue 29, 2009
From the journal:

Dalton Transactions

Neutral ligand induced methane elimination from rare-earth metal tetramethylaluminates up to the six-coordinate carbide state†

Ajay Venugopal,ab   Ina Kamps,a   Daniel Bojer,a   Raphael J. F. Berger,a   Andreas Mix,a   Alexander Willner,a   Beate Neumann,a   Hans-Georg Stammlera  and  Norbert W. Mitzel*ab  

* Corresponding authors

a Universität Bielefeld, Fakultät für Chemie, Anorganische Chemie und Strukturchemie Universitätsstraße 25, Bielefeld, Germany
E-mail: mitzel@uni-bielefeld.de
Fax: +49 (0)521 106-6026
Tel: +49 (0) 521 106-6163

b International Graduate School of Chemistry, Universität Münster, Corrensstraße 30, Münster, Germany

Abstract

The reaction of 1,3,5-trimethyl-1,3,5-triazacyclohexane (TMTAC) with [La{Al(CH3)4}3] resulted in C–H activation, leading to the formation of [(TMTAC)La{Al(CH3)4}{(μ3-CH2)[Al(CH3)2(μ2-CH3)]2}] (1) containing a bis(aluminate) dianion and subsequent extrusion of methane. A similar reaction with [Y{Al(CH3)4}3] led to the formation of CH4, [TMTAC{Al(CH3)3}2] (2) and {[(TMTAC)Y][Y2(μ2-CH3)][{(μ6-C)[Al(μ2-CH3)2(CH3)]3}{(μ3-CH2)(μ2-CH3)Al(CH3)2}2] (3), containing a six-coordinate carbide ion and two [CH2Al(CH3)3]2− anions. Compound 3 is a product of multiple C–H activation. This reaction was monitored by in situ1H NMR spectroscopy. The analogous reaction with [Sm{Al(CH3)4}3] led to the formation of 2, of [(TMTAC)Sm{(μ2-CH3)(CH3)2Al}2{(μ3-CH2)2Al(CH3)2}2] (4), which contains a tris(aluminate) trianion, and [{(TMTAC)Sm}{Sm2(μ2-CH3)}{(μ6-C)[Al(μ2-CH3)2(CH3)]3}{(μ3-CH2)(μ2-CH3)Al(CH3)2}2] (5), which is isostructural to 3. The products were characterised by elemental analyses (except 4, 5), 1 by multinuclear NMR spectroscopy and compounds 1, 2, 3, 4 and 5 by X-ray crystallography. Quantumchemical calculations were undertaken to support the crystallographic data analysis and confirm the structure of 3 and to compare it with an analogous compound where the central six-coordinate carbon has been replaced by oxygen. The investigations point to a mechanism of sterically induced condensation of [Al(CH3)4]−groups in close proximity in the coordination spheres of the rare-earth metal atoms, which is dependent on the size of these metal atoms.

Graphical abstract: Neutral ligand induced methane elimination from rare-earth metal tetramethylaluminates up to the six-coordinate carbide state

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Article information

DOI
https://doi.org/10.1039/B905271B
Article type
Paper
Submitted
16 Mar 2009
Accepted
01 May 2009
First published
16 Jun 2009

Dalton Trans., 2009, 5755-5765

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Neutral ligand induced methane elimination from rare-earth metal tetramethylaluminates up to the six-coordinate carbide state

A. Venugopal, I. Kamps, D. Bojer, R. J. F. Berger, A. Mix, A. Willner, B. Neumann, H. Stammler and N. W. Mitzel, Dalton Trans., 2009, 5755 DOI: 10.1039/B905271B

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