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Probing the Redox Chemistry of Titanium Silicalite‐1: Formation of Tetrahedral Ti 3+ Centers by Reaction with Triethylaluminum
Author(s) -
Morra Elena,
Giamello Elio,
Chiesa Mario
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201304139
Subject(s) - titanium , redox , tetrahedron , chemistry , inorganic chemistry , crystallography , organic chemistry
Transition‐metal ions with open‐shell configurations hold promise in the development of novel coordination chemistry and potentially unprecedented redox catalysis. Framework‐substituted Ti 3+ ions with tetrahedral coordination are generated by reductive activation of titanium silicalite‐1 with triethylaluminum, an indispensable co‐catalyst for heterogeneous Ziegler–Natta polymerization catalysts. Continuous‐wave and pulse electron paramagnetic resonance methods are applied to unravel details on the local environment of the reduced transition metal‐ions, which are shown to be part of the silica framework by detection of 29 Si hyperfine interactions. The chemical accessibility of the reduced sites is probed using ammonia as probe molecule. Evidence is found for the coordination of a single ammonia molecule. Comparison to similar systems, such as TiAlPO‐5, reveals clear differences in the coordination chemistry of the reduced Ti sites in the two solids, which may be understood considering the different electronic properties of the solid frameworks.