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New Volatile Tantalum Imido Precursors with Carboxamide Ligands

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journal contribution
posted on 16.09.2021, 06:14 by Jeong Min Hwang, Sung Kwang Lee, Sunyoung Shin, Ji-Seoung Jeong, Hae Sun Kim, Ji Yeon Ryu, Taeyong Eom, Bo Keun Park, Chang Gyoun Kim, Taek-Mo Chung
A series of Ta­(V) tBu-imido/N-alkoxy carboxamide complexes, TaCl2(NtBu)­(pyridine)­(edpa) (1), TaCl­(NtBu)­(edpa)2 (2), Ta­(NtBu)­(edpa)3 (3), TaCl2(NtBu)­(pyridine)­(mdpa) (4), and Ta­(NtBu)­(mdpa)3 (5), were successfully synthesized by metathesis reactions between Ta­(NtBu)­Cl3(py)2 and several equivalents of Na­(edpa) (edpaH = N-ethoxy-2,2-dimethylpropanamide) and Na­(mdpa) (mdpaH = N-methoxy-2,2-dimethylpropanamide). Furthermore, complexes 3 and 5 were simply transformed to new dimeric structures [Ta­(μ2–O)­(edpa)3]2 (6) and [Ta­(μ2–O)­(mdpa)3]2 (7) with the elimination of the NtBu imido group by air exposure. Compounds 17 were characterized by 1H and 13C nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis (TGA), and single-crystal X-ray diffraction. Single-crystal X-ray diffraction analysis revealed that complexes 3 and 5 have a distorted pentagonal bipyramidal geometry around the central Ta atom, with three monoanionic bidentate N-alkoxy carboxamide ligands and one tBu imido ligand saturating the coordination of tantalum ions. TGA revealed that complexes 3 and 5 had superior thermal characteristics and stability. These complexes could potentially be applied as precursors for tantalum oxide thin films.