Department of Chemistry, National Dong Hwa University, Hualien, Taiwan 97401, ROC.
Inorg Chem. 2012 Jun 18;51(12):6577-91. doi: 10.1021/ic300135w. Epub 2012 Jun 4.
Reactions of Cu(I) salts with Na(S(2)CR) (R = N(n)Pr(2), NEt(2), aza-15-crown-5), and (Bu(4)N)(BH(4)) in an 8:6:1 ratio in CH(3)CN solution at room temperature yield the monocationic hydride-centered octanuclear Cu(I) clusters, Cu(8)(H){S(2)CR}(6) (R = N(n)Pr(2), 1(H); NEt(2), 2(H); aza-15-crown-5, 3(H)). Further reactions of Cu(8)(H){S(2)CR}(6) with 1 equiv of (Bu(4)N)(BH(4)) produced neutral heptanuclear copper clusters, [Cu(7)(H){S(2)CR}(6)] (R = N(n)Pr(2), 4(H); NEt(2), 5(H); aza-15-crown-5, 6(H)) and clusters 4-6 can also be generated from the reaction of Cu(BF(4))(2), Na(S(2)CR), and (Bu(4)N)(BH(4)) in a 7:6:8 molar ratio in CH(3)CN. Reformation of cationic Cu(I)(8) 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){S(2)CN(n)Pr(2)}(6) can be oxidatively removed as H(2) by Ce(NO(3))(6)(2-) to yield [Cu(II)(S(2)CN(n)Pr(2))(2)] exploiting the redox-tolerant nature of dithiocarbamates. Regeneration of hydride-centered octanuclear copper clusters from the [Cu(II)(S(2)CN(n)Pr(2))(2)] can be achieved by reaction with Cu(I) ions and borohydride. The hydride release and regeneration of Cu(I)(8) was monitored by UV-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 (1)H NMR, FT-IR, UV-vis, and elemental analysis, and molecular structures of 1(H), 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 (μ(2), μ(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.
铜（I）盐与 Na(S(2)CR)（R = N(n)Pr(2)，NEt(2)，aza-15-冠-5）以及（Bu(4)N)(BH(4))在室温下以 8:6:1 的比例在 CH(3)CN 溶液中反应，生成单核氢中心的八核铜（I）簇合物Cu(8)(H){S(2)CR}(6)（R = N(n)Pr(2)，1(H)；NEt(2)，2(H)；aza-15-冠-5，3(H)）。进一步反应Cu(8)(H){S(2)CR}(6)与 1 当量的（Bu(4)N)(BH(4))反应生成中性的七核铜簇合物[Cu(7)(H){S(2)CR}(6)]（R = N(n)Pr(2)，4(H)；NEt(2)，5(H)；aza-15-冠-5，6(H)），并且簇合物 4-6 也可以通过在 CH(3)CN 中以 7:6:8 的摩尔比反应 Cu(BF(4))(2)、Na(S(2)CR)和（Bu(4)N)(BH(4))生成。在溶液中加入 1 当量的铜（I）盐可以观察到阳离子 Cu(I)(8)簇的重新形成。有趣的是，Cu(8)(H){S(2)CN(n)Pr(2)}(6)中的中心氢可以通过 Ce(NO(3))(6)(2-)氧化去除为 H(2)，利用二硫代氨基甲酸盐的氧化还原耐受性质。从[Cu(II)(S(2)CN(n)Pr(2))(2)]可以通过与铜（I）离子和硼氢化钠反应再生氢中心的八核铜簇合物。通过 UV-可见滴定实验监测氢化物的释放和再生。据我们所知，这是第一次可以通过化学手段将铜簇合物内的氢化物释放为 H(2)。所有配合物均通过（1）H NMR、FT-IR、UV-vis 和元素分析进行了充分表征，并且通过单晶 X 射线衍射清楚地确定了 1(H)、2(H)和 6(H)的分子结构。1(H)和 2(H)均表现出四面体形的 Cu(8)骨架，该骨架被由六个二烷基二硫代氨基甲酸盐配体组成的 S(12)二十面体所包含，采用四金属四连接（μ(2)，μ(2))键合模式。6(H)的铜骨架是一个扭曲的三角锥形，通过单晶中子衍射证明四配位的氢化物占据中心位置。化合物 1-3 在固态和在 77 K 下紫外照射下的溶液中均表现出黄色发射，无结构的发射被分配为（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）和时变密度泛函理论（TDDFT）计算与实验结构相匹配，并提供了对其键合和光学性质的合理化解释。
