Unusual Structural Types in Nickel Cluster Chemistry from the Use of Pyridyl Oximes: Ni5, Ni12Na2, and Ni14 Clusters

Syntheses, crystal structures, and magnetochemical characterization are reported for the three new nickel(II) clusters [Ni14(OH)4(N3)8(pao)14(paoH)2(H2O)2](ClO4)2 (1), [Ni12Na2(OH)4(N3)8(pao)12(H2O)10](OH)2 (2), and [Ni5(ppko)5(H2O)7](NO3)5 (3) (paoH = pyridine-2-carbaldehyde oxime, ppkoH = di-2-pyridyl ketone oxime). The reaction of Ni(ClO4)2·6H2O with paoH and NBun4N3 in H2O/MeCN in the presence of NEt3, gave 1 in 65% yield. Complex 2 was obtained in 60% yield from the reaction of NiCl2·6H2O with paoH and NaN3 in H2O/MeCN in the presence of NaOH. The reaction of Ni(NO3)2·6H2O with ppkoH in EtOH in the presence of LiOH afforded complex 3 in 75% yield. The complexes all contain novel core topologies. The core of 1 comprises a central Ni4 rhombus between two Ni5. Complex 1 is the largest metal/oxime cluster discovered to date, as well as the first NiII14 coordination complex and the largest NiII/N3− cluster. Complex 2 has a Ni12Na2 topology that is very similar to that of 1, but with two central NiII atoms of 1 replaced with NaI atoms. The core of 3 consists of four NiII atoms forming a highly distorted tetrahedron, with the fifth NiII atom lying almost on one of the edges. Variable-temperature, solid-state dc susceptibility and magnetization studies were carried out on complexes 1−3, and these were complemented with ac susceptibility data for 1 and 2. Fitting of the obtained M/(NμB) vs H/T data by matrix diagonalization and including axial zero-field splitting (D) gave ground-state spin (S) and D values of S = 6, D = −0.12(3) cm−1 for 1 and S = 3, D = −0.20(5) cm−1 for each of the two essentially noninteracting S = 3 Ni6 subunits of 2. The data for 3 indicate antiferromagnetic exchange interactions and an S = 1 ground state. A simple 2-J model was found to be adequate to describe the variable-temperature dc susceptibility data. The combined work demonstrates the ligating flexibility of pao− and ppko−, and their usefulness in the synthesis of polynuclear Nix clusters with or without the presence of ancillary ligands.

本研究报告了三种新型镍(II)簇[Ni14(OH)4(N3)8(pao)14(paoH)2(H2O)2](ClO4)2 (1), [Ni12Na2(OH)4(N3)8(pao)12(H2O)10](OH)2 (2), 以及 [Ni5(ppko)5(H2O)7](NO3)5 (3) 的合成、晶体结构和磁化学特性（其中paoH = 吡啶-2-甲酰腙，ppkoH = 双-2-吡啶基酮腙）。在NEt3存在下，Ni(ClO4)2·6H2O与paoH和NBun4N3在H2O/MeCN溶液中的反应，以65%的产率得到1。通过NiCl2·6H2O与paoH和NaN3在H2O/MeCN溶液中，并在NaOH存在下反应，以60%的产率获得2。在LiOH存在下，Ni(NO3)2·6H2O与ppkoH在EtOH溶液中的反应，以75%的产率得到3。这些配合物均包含新颖的核心拓扑结构。1的核心由两个Ni5之间的中央Ni4菱形构成。1是目前发现的最大的金属/腙簇，同时也是首个NiII14配位复合物以及最大的NiII/N3−簇。2具有与1非常相似的Ni12Na2拓扑结构，但将1中的两个中央NiII原子替换为NaI原子。3的核心由四个NiII原子形成一个高度扭曲的四面体，第五个NiII原子几乎位于一个边角。对1-3进行了变温固态直流磁化率和磁化率研究，并辅以1和2的交流磁化率数据。通过矩阵对角化拟合M/(NμB) vs H/T数据，并包括轴向零场分裂（D），得到了1的基态自旋（S）和D值为S = 6, D = −0.12(3) cm−1，以及2的两个几乎不相互作用的S = 3 Ni6亚单元的S = 3, D = −0.20(5) cm−1。3的数据表明存在反铁磁交换作用和一个S = 1基态。一个简单的2-J模型足以描述变温直流磁化率数据。这项联合研究展示了pao−和ppko−的配位灵活性，以及它们在合成带有或无辅助配体的多核Nix簇中的有用性。