Lu Taotao, Liu Zhiming, Steren Carlos A, Fei Fan, Cook Tabitha M, Chen Xue-Tai, Xue Zi-Ling
State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.
Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
Dalton Trans. 2018 Mar 28;47(12):4282-4292. doi: 10.1039/c7dt04666a. Epub 2018 Feb 28.
A series of Ni(ii), Pd(ii) and Pt(ii) complexes [ML][PF] [L = L, M = Ni (1), Pd (2), Pt (3); L = L, M = Ni (4), Pd (5), Pt (6)] and [Pt(L)(acac)] (7) have been prepared by the reactions of two tetradentate macrocyclic amine-NHC ligand precursors, [HL][PF] and [HL][PF], with Ni(OAc)·4HO, Pd(OAc) and Pt(acac) in the presence of NaOAc. Complex 7 is isolated along with 6 from the same reaction between [HL][PF] and Pt(acac). There are two atropisomers in 1-3 and two achiral conformers in 4-6. The crystal structures of 1-3 and one conformer of 4-6 (4a-6a) have been determined by single-crystal X-ray diffraction studies. The metal ion is found to reside in the cavity of the macrocyclic ring and adopts a square-planar configuration. Detailed NMR studies including variable-temperature NMR spectroscopy reveal a dynamic interconverting process between two atropisomers of 1-3 in the solutions via a ring twisting mechanism. Two conformers in the equilibrated solution of 4-6, probably arising from the orientation of two amine N-H bonds with respect to the coordination plane, exchange slowly. Time-dependent H NMR spectra show that one conformer (4a-6a) in solution converts into the other (4b-6b) via the inversion of the nitrogen atom.
通过两种四齿大环胺 - NHC配体前体[HL][PF]和[HL][PF]与Ni(OAc)·4H₂O、Pd(OAc)₂和Pt(acac)₂在NaOAc存在下反应，制备了一系列Ni(ii)、Pd(ii)和Pt(ii)配合物[ML][PF₆] [L = L₁，M = Ni (1)，Pd (2)，Pt (3)；L = L₂，M = Ni (4)，Pd (5)，Pt (6)]以及[Pt(L₁)(acac)] (7)。配合物7与6是在[HL][PF₆]和Pt(acac)₂的相同反应中分离得到的。1 - 3中有两种阻转异构体，4 - 6中有两种非手性构象体。通过单晶X射线衍射研究确定了1 - 3以及4 - 6的一种构象体（4a - 6a）的晶体结构。发现金属离子位于大环环腔内并采用平面正方形构型。详细的NMR研究，包括变温NMR光谱，揭示了溶液中1 - 3的两种阻转异构体通过环扭转机制进行动态互变过程。4 - 6平衡溶液中的两种构象体可能源于两个胺N - H键相对于配位平面的取向，它们交换缓慢。时间相关的¹H NMR光谱表明，溶液中的一种构象体（4a - 6a）通过氮原子的翻转转化为另一种（4b - 6b）。
