4-Tetrafluoropyridyl Silver(I), AgC₅F₄N, in Redox Transmetalations with Selenium and Tellurium

Se­(C₅F₄N)₂ and Te­(C₅F₄N)₂ were prepared via redox transmetalations of AgC₅F₄N and the corresponding elements in good yields. The crystal structures of both derivatives exhibit infinite chains caused by a weak intermolecular contact between the chalcogen and one nitrogen atom with a T-shaped (ψ-pentagonal-bipyramidal) ligand arrangement. Crystallization of both reagents from dimethylsulfoxide gave single crystals of the corresponding 1:1 adducts that crystallize in infinite chains best expressed by the formula [E­(C₅F₄N)₂·(μ-DMSO)]_∞ (E = Se, Te). In these cases, the coordination spheres of selenium and tellurium are square-planar (ψ-octahedral). Similar effects are found in the molecular structures of [Te­(C₅F₄N)₂·TMTU]_∞ and [Te­(C₆F₅)₂·TMTU]_∞ (TMTU = tetramethylthiourea). Differences in the Te–S interatomic distances clearly indicate the C₅F₄N ligand being significantly more electron-withdrawing in comparison with the C₆F₅ group; that is, Te­(C₅F₄N)₂ is the stronger Lewis acid

4-Tetrafluoropyridyl Silver(I), AgC₅F₄N, in Redox Transmetalations with Selenium and Tellurium

Se­(C₅F₄N)₂ and Te­(C₅F₄N)₂ were prepared via redox transmetalations of AgC₅F₄N and the corresponding elements in good yields. The crystal structures of both derivatives exhibit infinite chains caused by a weak intermolecular contact between the chalcogen and one nitrogen atom with a T-shaped (ψ-pentagonal-bipyramidal) ligand arrangement. Crystallization of both reagents from dimethylsulfoxide gave single crystals of the corresponding 1:1 adducts that crystallize in infinite chains best expressed by the formula [E­(C₅F₄N)₂·(μ-DMSO)]_∞ (E = Se, Te). In these cases, the coordination spheres of selenium and tellurium are square-planar (ψ-octahedral). Similar effects are found in the molecular structures of [Te­(C₅F₄N)₂·TMTU]_∞ and [Te­(C₆F₅)₂·TMTU]_∞ (TMTU = tetramethylthiourea). Differences in the Te–S interatomic distances clearly indicate the C₅F₄N ligand being significantly more electron-withdrawing in comparison with the C₆F₅ group; that is, Te­(C₅F₄N)₂ is the stronger Lewis acid

Design of Volatile Mixed-Ligand Tantalum(V) Compounds as Precursors to Ta₂O₅ Films

Synthesis and structural characterization of six monomeric, heteroleptic tantalum­(V) complexes of the general formula Ta­(O^<i>i</i>Pr)₄(ArTFP), where Ar = pyridine (<b>1</b>), 4,5- dimethyloxazole (<b>2</b>), 4,5-dimethylthiazole (<b>3</b>), benzimidazole (<b>4</b>), benzoxazole (<b>5</b>), benzthiazole (<b>6</b>), and TFP = trifluoropropenol, are described. Introduction of a donor-functionalized β-heteroarylalkenolate in the coordination sphere of Ta in the dimeric Ta₂(O^<i>i</i>Pr)₁₀ increases significantly the stability and volatility of these precursors, simplifying the depositions of Ta₂O₅. The molecular structures of <b>1</b>–<b>6</b> exhibited a distorted octahedral coordination around the tantalum center by four isopropoxide groups and one β-heteroarylalkenolate. Thermal decomposition studies (TG/DTA) and analysis of byproducts by NMR spectroscopy confirmed the decomposition mechanism and gas-phase stability of the heteroleptic compounds necessary for Ta₂O₅ depositions. Chemical vapor deposition studies with <b>1</b> and <b>2</b> demonstrated their suitability as efficient precursors for the growth of Ta₂O₅ thin films, whose properties were compared with Ta₂O₅ thin films obtained from homoleptic alkoxides