Issue 4, 2002
From the journal:

Physical Chemistry Chemical Physics

Mesoporous silica grafted with multiply bonded dimolybdenum cations: XAFS analysis and catalytic activity in cyclopentadiene polymerisation†

Martyn Pillinger,a   Isabel S. Gonçalves,*ab   André D. Lopes,c   Paula Ferreira,b   João Rocha,a   Guofang Zhang,b   Marcus Schäfer,d   Oskar Nuykend  and  Fritz E. Kühn*b  

* Corresponding authors

a Department of Chemistry, University of Aveiro, Aveiro, Portugal
E-mail: igoncalves@dq.ua.pt
Fax: 351 234 370084

b Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstrasse 4, Garching bei München, Germany
E-mail: fritz.kuehn@ch.tum.de
Fax: 49 (0)89 289 13473

c Department of Chemistry, University of the Algarve, Campus de Gambelas, Faro, Portugal
E-mail: adlopes@ualg.pt
Fax: 351 289 819403

d Lehrstuhl für Makromolekulare Stoffe der Technischen Universität München, Lichtenbergstrasse 4, Garching bei München, Germany
E-mail: oskar.nuyken@ch.tum.de
Fax: 49 (0)89 289 13563

Abstract

Molybdenum K-edge X-ray absorption fine structure (XAFS) spectroscopy has been used to characterise the local structure around the metal centres in mesoporous silica MCM-41 derivatised with the complex salts [Mo2(µ-O2CCH3)2(CH3CN)6](BF4)2, [Mo2(µ-CH3CONH)2(CH3CN)4](BF4)2, [Mo2(CH3CN)10](BF4)4 and [Mo2(µ-O2CCH3)2(dppa)2(CH3CN)2](BF4)2. Analysis of the EXAFS reveals that the molybdenum–molybdenum quadruple bond is retained in the grafted materials and that the equatorially coordinated ligands are not displaced. The results support the assumption that the complexes are immobilised on the silica surface by an interaction with silanol groups in axial positions. Consistent with these findings, catalysis tests show that the activities of the supported dimolybdenum complexes as initiators for the polymerisation of cyclopentadiene are comparable with those observed for the free complexes in the homogeneous phase. The XAFS results also reveal that air-oxidation of the supported catalysts leads to the rapid formation of surface-fixed dioxo-bridged binuclear species, characterised by a molybdenum–molybdenum interatomic distance of 2.56 ± 0.02 Å.

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Article information

DOI
https://doi.org/10.1039/B108320A
Article type
Paper
Submitted
14 Sep 2001
Accepted
30 Nov 2001
First published
18 Jan 2002

Phys. Chem. Chem. Phys., 2002,4, 696-702

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Mesoporous silica grafted with multiply bonded dimolybdenum cations: XAFS analysis and catalytic activity in cyclopentadiene polymerisation

M. Pillinger, I. S. Gonçalves, A. D. Lopes, P. Ferreira, J. Rocha, G. Zhang, M. Schäfer, O. Nuyken and F. E. Kühn, Phys. Chem. Chem. Phys., 2002, 4, 696 DOI: 10.1039/B108320A

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