Effect of Counteranions in Electrocatalytic Hydrogen Generation Promoted by Bis(phosphinopyridyl) Ni(II) Complexes
Effect of Counteranions in Electrocatalytic Hydrogen Generation Promoted by Bis(phosphinopyridyl) Ni(II) Complexes
复制标题
抗衡阴离子在双(膦基吡啶基)Ni(II)配合物促进电催化制氢中的作用
DOI：
10.1021/acs.inorgchem.0c03657
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发表时间：
2021
影响因子：
4.6
通讯作者：
Masuda Hideki
中科院分区：
文献类型：
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作者：
Kato Takuma;Tatematsu Ryo;Nakao Kenichi;Inomata Tomohiko;Ozawa Tomohiro;Masuda Hideki
我们之前报道了能够电催化产氢的 Ni(II) 配合物的制备和表征。络合物 [Ni(LNH2)2Cl]Cl (1) 包含一个 6-((二苯基膦基)甲基)吡啶-2-胺配体 (LNH2)，该配体具有一个氨基作为碱基，由于其位置靠近金属中心而充当质子转移位点。为了研究抗衡阴离子在氢气生成中的影响，合成了另外两种具有弱配位/非配位抗衡阴离子的 NiII(LNH2) 配合物，[Ni(LNH2)2](OTs)2(OTs–=对甲苯磺酸盐) (2) 和 [Ni(LNH2)2](BF4)2(3)。它们的 X 射线晶体结构表明 Ni(II) 离子与两种配合物中的两个二齿 LNH2 配体配位。复合物2在晶胞中包含反式和顺式异构体。前者呈轴向拉长的方形锥体几何形状（τ5=0.17），后者呈近方形平面几何形状（τ4=0.11），在轴向位置有两个弱相互作用的OTs-阴离子。 Complex3在固态时只有顺异构体，其平面几何形状接近正方形（τ4= 0.10）。这些配合物与 1 略有不同，后者具有扭曲的方锥体几何形状 (τ5= 0.25)，并具有配位的氯离子。 MeCN 中 2 和 3 的紫外可见光谱显示出方形平面 Ni(II) 配合物的光谱图案特征。这些光谱与 1 的独特光谱略有不同，后者是典型的轴向配位 Ni(II) 物质的光谱，因为在顶端位置有一个 Cl-阴离子。这三种 Ni(II) 配合物 (1.0 mmol) 促进的电催化氢生成表明，逐步添加 HOAc（MeCN 中的 pKa = 22.3）作为质子源会导致催化电流增加。该配合物在含有 0.1 M [n-Bu4N](ClO4) 的 MeCN (3 mL) 中，在 HOAc（145 当量）存在下，过电势约为 3800 s–1for1、5400 s–1for2 和 8800 s–1for3，显示转换频率 (TOF) 为 3800 s–1for1、5400 s–1for2 和 8800 s–1for3。分别为 530、490 和 430 mV。
We previously reported the preparation and characterization of a Ni(II) complex capable of electrocatalytic hydrogen generation. The complex [Ni(LNH2)2Cl]Cl (1) includes a 6-((diphenylphosphino)methyl)pyridin-2-amine ligand (LNH2), which has an amino group as a base that acts as a proton transfer site by virtue of its location near the metal center. In order to study the effect of counteranions in hydrogen generation, two additional NiII(LNH2) complexes with weakly coordinating/noncoordinating counteranions, [Ni(LNH2)2](OTs)2(OTs–=p-toluenesulfonate) (2) and [Ni(LNH2)2](BF4)2(3), were synthesized. Their X-ray crystal structures reveal that the Ni(II) ion is coordinated with two bidentateLNH2ligands in both complexes. Complex2contains bothtransandcisisomers in the unit cell. The former is in an axially elongated square-pyramidal geometry (τ5= 0.17), and the latter is in a nearly square planar geometry (τ4= 0.11) with two weakly interacting OTs–anions at the axial sites. Complex3has only thecisisomer in the solid state, which is in a nearly square planar geometry (τ4= 0.10). These complexes are slightly different from1, which has a distorted-square-pyramidal geometry (τ5= 0.25) with a coordinated chloride anion. UV–vis spectra of2and3in MeCN show a spectral pattern characteristic of a square-planar Ni(II) complex. These spectra are slightly different from the unique spectrum of1, which is typical of an axially coordinating Ni(II) species as a result of having a Cl–anion at the apical position. Electrocatalytic hydrogen generation promoted by these three Ni(II) complexes (1.0 mmol) demonstrates an increase in the catalytic current induced by stepwise addition of HOAc (pKa= 22.3 in MeCN) as a proton source. The complexes demonstrate turnover frequencies (TOF) of 3800 s–1for1, 5400 s–1for2, and 8800 s–1for3in MeCN (3 mL) containing 0.1 M [n-Bu4N](ClO4) in the presence of HOAc (145 equiv) at overpotentials of ca. 530, 490, and 430 mV, respectively.