M-Ge-Si thermolytic molecular precursors and models for germanium-doped transition metal sites on silica

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 53; no. 17; pp. 734 - 7349
• Main Authors: Dombrowski, James P, Kalendra, Vidmantas, Ziegler, Micah S, Lakshmi, K. V, Bell, Alexis T, Tilley, T. Don
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 30.04.2024; Royal Society of Chemistry (RSC)
• Subjects: Chemical synthesis; Electron paramagnetic resonance; Germanium; Grafting; Iron; Ligands; NMR; Nuclear magnetic resonance; Organometallic compounds; Oxidation; Precursors; Silicon dioxide; Single crystals; Thermogravimetric analysis; Transition metals; Valence
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d4dt00644e

The synthesis, thermolysis, and surface organometallic chemistry of thermolytic molecular precursors based on a new germanosilicate ligand platform, -OGe[OSi(O t Bu) 3 ] 3 , is described. Use of this ligand is demonstrated with preparation of complexes containing the first-row transition metals Cr, Mn, and Fe. The thermolysis and grafting behavior of the synthesized complexes, Fe{OGe[OSi(O t Bu) 3 ] 3 } 2 ( FeGe ), Mn{OGe[OSi(O t Bu) 3 ] 3 } 2 (THF) 2 ( MnGe ) and Cr{OGe[OSi(O t Bu) 3 ] 3 } 2 (THF) 2 ( CrGe ), was evaluated using a combination of thermogravimetric analysis; nuclear magnetic resonance (NMR), ultraviolet-visible (UV-Vis), and electron paramagnetic resonance (EPR) spectroscopies; and single-crystal X-ray diffraction (XRD). Grafting of the precursors onto SBA-15 mesoporous silica and subsequent calcination in air led to substantial changes in transition metal coordination environments and oxidation states, the implications of which are discussed in the context of low-coordinate and low oxidation state thermolytic molecular precursors. The new siloxy-germoxy ligand HOGe[OSi(O t Bu) 3 ] 3 generates Mn-, Fe-, and Cr-containing precursors suitable for thermolytic molecular precursor routes to quaternary oxides.