New Volatile Tantalum Imido Precursors with Carboxamide Ligands

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 1–7 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.

一系列钽(V)叔丁基亚胺/N-烷氧基羧酰胺配合物，包括TaCl2(NtBu)(pyridine)(edpa)(1)、TaCl(NtBu)(edpa)2(2)、Ta(NtBu)(edpa)3(3)、TaCl2(NtBu)(pyridine)(mdpa)(4)以及Ta(NtBu)(mdpa)3(5)，通过钽叔丁基氯化物(py)2与多种当量的Na(edpa)(edpaH = N-乙氧基-2,2-二甲基丙酰胺)和Na(mdpa)(mdpaH = N-甲氧基-2,2-二甲基丙酰胺)之间的置换反应成功合成。此外，配合物3和5通过空气暴露去除NtBu亚胺基团，简单地转化为新的二聚结构[Ta(μ2–O)(edpa)3](6)和[Ta(μ2–O)(mdpa)3](7)。化合物1至7经1H和13C核磁共振波谱、傅里叶变换红外光谱、元素分析、热重分析(TGA)和单晶X射线衍射表征。单晶X射线衍射分析显示，配合物3和5在中心钽原子周围呈现畸变的五角双锥几何结构，其中三个单负电荷的双齿N-烷氧基羧酰胺配体和一个叔丁基亚胺配体饱和了钽离子的配位。热重分析揭示了配合物3和5具有卓越的热学特性和稳定性。这些配合物有望作为制备氧化钽薄膜的前驱体。