Hydrido Copper Clusters Supported by Dithiocarbamates: Oxidative Hydride Removal and Neutron Diffraction Analysis of [Cu7(H) {S2C(aza-15-crown-5)}6]
Hydrido Copper Clusters Supported by Dithiocarbamates: Oxidative Hydride Removal and Neutron Diffraction Analysis of [Cu7(H) {S2C(aza-15-crown-5)}6]
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DOI：
10.1021/ic300135w
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发表时间：
2012-06-18
影响因子：
4.6
通讯作者：
Liu, C. W.
中科院分区：
文献类型：
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作者：
Liao, Ping-Kuei;Fang, Ching-Shiang;Liu, C. W.
Cu（I）盐与Na（S2 CR）（R =（NPr 2）-Pr-n，NEt 2，aza-15-crown-5）和（Bu 4 N）（BH 4）以8：6：1的比例在室温下在CH 3CN溶液中反应，得到单阳离子的以双金属离子为中心的八核Cu-I簇合物[Cu-8（H）{S2 CR}（6）]（PF 6）（R =（NPr 2）-Pr-n，1（H）; NEt 2，2（H）; aza-15-crown-5，3（H））。[Cu-8（H）{S2 CR}（6）]（PF_6）与1当量（Bu_4N）（BH_4）进一步反应，生成中性七核铜簇合物[Cu-2（H）{S2 CR}（6）] =（NPr_2）-Pr_n，4（H）;氮杂-15-冠-5，6（H））和簇4-6也可以由Cu（BF 4）（2）、Na（S2 CR）和（Bu 4 N）（BH 4）以7：6：8的摩尔比在CH 3CN中反应生成。在中性Cu-7团簇中加入1当量的Cu-I盐，可使阳离子Cu-8（I）团簇发生再形成。有趣的是，[Cu-8（H）{（S2 CNPr 2）-Pr-n}（6）]（PF 6）中的中心氢化物可以通过Ce（NO3）（6）（2-）以H-2的形式氧化除去，从而产生[Cu-II（（S2 CNPr 2）-Pr-n）（2）]，这利用了二硫代氨基甲酸酯的氧化还原耐受性。[Cu-II（S_2CNnPr_2）（2）]与Cu（I）离子和硼氢化物反应，可再生出以硼氢化物为中心的八核铜簇合物.用紫外-可见滴定法对Cu-8（I）的放氢和再生过程进行了监测。据我们所知，这是第一次包裹在铜簇中的氢化物可以通过化学方法释放为H-2。所有配合物均通过H-1 NMR、FT-IR、UV-vis和元素分析进行了表征，并通过单晶X-射线衍射确定了2（H）和6（H）的分子结构。1（H）和2（H）均具有四帽四面体Cu-8骨架，该骨架内接于由六个二烷基二硫代氨基甲酸酯配体以四金属-四连接（mu（2），mu（2））键合模式构成的S-12二十面体内。单晶中子衍射表明，6（H）的铜骨架是一个三帽扭曲四面体，其中四配位氢化物占据中心位置。化合物1-3在固态和溶液中在77 K的紫外光照射下都显示出黄色发射，并且无结构发射被指定为（3）金属到配体电荷转移（MLCT）激发态。模型化合物的密度泛函理论（DFT）和含时密度泛函理论（TDDFT）计算与实验结构相匹配，并提供了它们的键合和光学性质的合理化。
Reactions of Cu(I) salts with Na(S2CR) (R = (NPr2)-Pr-n, NEt2, aza-15-crown-5), and (Bu4N)(BH4) in an 8:6:1 ratio in CH3CN solution at room temperature yield the monocationic hydride-centered octanuclear Cu-I clusters, [Cu-8(H){S2CR}(6)](PF6) (R = (NPr2)-Pr-n, 1(H); NEt2, 2(H); aza-15-crown-5, 3(H)). Further reactions of [Cu-8(H){S2CR}(6)](PF6) with 1 equiv of (Bu4N) (BH4) produced neutral heptanuclear copper clusters, [Cu-2(H){S2CR}(6)] = (NPr2)-Pr-n, 4(H); NEt2, 5(H); aza-15-crown-5, 6(H)) and clusters 4-6 can also be generated from the reaction of Cu(BF4)(2), Na(S2CR), and (Bu4N)(BH4) in a 7:6:8 molar ratio in CH3CN. Reformation of cationic Cu-8(I) clusters by adding 1 equiv of Cu-I salt to the neutral Cu-7 clusters in solution is observed. Intriguingly, the central hydride in [Cu-8(H){(S2CNPr2)-Pr-n}(6)](PF6) can be oxidatively removed as H-2 by Ce(NO3)(6)(2-) to yield [Cu-II((S2CNPr2)-Pr-n)(2)] exploiting the redox-tolerant nature of dithiocarbamates. Regeneration of hydride-centered octanuclear copper clusters from the [Cu-II(S2CNnPr2)(2)] can be achieved by reaction with Cu(I) ions and borohydride. The hydride release and regeneration of Cu-8(I) was monitored by U-visible titration experiments. To our knowledge, this is the first time that hydride encapsulated within a copper cluster can be released as H-2 via chemical means. All complexes have been fully characterized by H-1 NMR, FT-IR, UV-vis, and elemental analysis, and molecular structures of 2(H), and 6(H) were clearly established by single-crystal X-ray diffraction. Both 1(H) and 2(H) exhibit a tetracapped tetrahedral Cu-8 skeleton, which is inscribed within a S-12 icosahedron constituted by six dialkyl dithiocarbamate ligands in a tetrametallic-tetraconnective (mu(2), mu(2)) bonding mode. The copper framework of 6(H) is a tricapped distorted tetrahedron in which the four-coordinate hydride is demonstrated to occupy the central site by single crystal neutron diffraction. Compounds 1-3 exhibit a yellow emission in both the solid state and in solution under UV irradiation at 77 K, and the structureless emission is assigned as a (3)metal to ligand charge transfer (MLCT) excited state. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations on model compounds match the experimental structures and provide rationalization of their bonding and optical properties.