High- and Mid-Valent Tantalum and Mono(peralkylcyclopentadienyl)tantalum Complexes of the Bicyclic Guanidinate Hexahydropyrimidopyrimidinate
| Autor: | Ross D. Bemowski, Louis Messerle, Dale C. Swenson, Adil Mohammad, Justine R. Olson, David A. Rotsch |
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| Rok vydání: | 2013 |
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| Zdroj: | Organometallics. 32:6232-6239 |
| ISSN: | 1520-6041 0276-7333 |
| Popis: | Ta(hpp)Cl4, Ta(hpp)2Cl3, and (η-C5Me4R)Ta(hpp)Cl3 (R = Me, Et; hpp = anion of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, hppH) are readily formed in good to excellent yields by addition of (hpp)SiMe3 to TaCl5, Ta(hpp)Cl4, or (η-C5Me4R)TaCl4, respectively, in dichloromethane. Ta(hpp)Cl4 in solution exhibits three CH2 multiplets in the proton NMR spectrum, consistent with a mirror plane that bisects the hpp ligand. The six-coordinate, yellow Ta(hpp)Cl4 possesses a distorted octahedral solid-state structure with chelating hpp and Ta–N distances of 2.038(1) and 2.059(1) A. Ta(hpp)2Cl3 is fluxional in solution by proton NMR spectroscopy, with three CH2 multiplets at room temperature that split into additional multiplets at −50 °C, consistent with the six multiplets expected from the solid-state structure. In the solid state, bright yellow Ta(hpp)2Cl3 has an approximately pentagonal bipyramidal structure with both hpp chelates coordinated in the pentagonal plane. Ta–N distances are 2.114(3) and 2.110(3... |
| Databáze: | OpenAIRE |
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