Hydrido Copper Clusters Supported by Dithiocarbamates: Oxidative Hydride Removal and Neutron Diffraction Analysis of [Cu₇(H){S₂C(aza-15-crown-5)}₆]

Reactions of Cu­(I) salts with Na­(S₂CR) (R = N^<i>n</i>Pr₂, 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, [Cu₈(H)­{S₂CR}₆]­(PF₆) (R = N^<i>n</i>Pr₂, <b>1</b>_<b>H</b>; NEt₂, <b>2</b>_<b>H</b>; aza-15-crown-5, <b>3</b>_<b>H</b>). Further reactions of [Cu₈(H)­{S₂CR}₆]­(PF₆) with 1 equiv of (Bu₄N)­(BH₄) produced neutral heptanuclear copper clusters, [Cu₇(H)­{S₂CR}₆] (R = N^<i>n</i>Pr₂, <b>4</b>_<b>H</b>; NEt₂, <b>5</b>_<b>H</b>; aza-15-crown-5, <b>6</b>_<b>H</b>) and clusters <b>4</b>–<b>6</b> 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^I₈ clusters by adding 1 equiv of Cu^I salt to the neutral Cu₇ clusters in solution is observed. Intriguingly, the central hydride in [Cu₈(H)­{S₂CN^<i>n</i>Pr₂}₆]­(PF₆) can be oxidatively removed as H₂ by Ce­(NO₃)₆^2– to yield [Cu^II(S₂CN^<i>n</i>Pr₂)₂] exploiting the redox-tolerant nature of dithiocarbamates. Regeneration of hydride-centered octanuclear copper clusters from the [Cu^II(S₂CN^<i>n</i>Pr₂)₂] can be achieved by reaction with Cu­(I) ions and borohydride. The hydride release and regeneration of Cu^I₈ 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 H₂ via chemical means. All complexes have been fully characterized by ¹H NMR, FT-IR, UV–vis, and elemental analysis, and molecular structures of <b>1</b>_<b>H</b>, <b>2</b>_<b>H</b>, and <b>6</b>_<b>H</b> were clearly established by single-crystal X-ray diffraction. Both <b>1</b>_<b>H</b> and <b>2</b>_<b>H</b> exhibit a tetracapped tetrahedral Cu₈ skeleton, which is inscribed within a S₁₂ icosahedron constituted by six dialkyl dithiocarbamate ligands in a tetrametallic-tetraconnective (μ₂, μ₂) bonding mode. The copper framework of <b>6</b>_<b>H</b> is a tricapped distorted tetrahedron in which the four-coordinate hydride is demonstrated to occupy the central site by single crystal neutron diffraction. Compounds <b>1</b>–<b>3</b> 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 ³metal 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

A Nanospheric Polyhydrido Copper Cluster of Elongated Triangular Orthobicupola Array: Liberation of H₂ from Solar Energy

An unprecedented air-stable, nanospheric polyhydrido copper cluster, [Cu₂₀H₁₁(S₂P­(OⁱPr)₂)₉] (<b>1</b>_<b>H</b>), which is the first example of an elongated triangular orthobicupola array of Cu atoms having <i>C</i>_3<i>h</i> symmetry, was synthesized and characterized. Its composition was primarily determined by electrospray ionization mass spectrometry, and it was fully characterized by ¹H, ²H, and ³¹P NMR spectroscopy and single-crystal X-ray diffraction (XRD). The structure of complex <b>1</b>_<b>H</b> can be expressed in terms of a trigonal-bipyramidal [Cu₂H₅]^3– unit anchored within an elongated triangular orthobicupola containing 18 Cu atoms, which is further stabilized by 18 S atoms from nine dithiophosphate ligands and six capping hydrides. The positions of the 11 hydrides revealed by low temperature XRD were supported by a density functional theory investigation on the simplified model [Cu₂₀H₁₁(S₂PH₂)₉] with <i>C</i>_3<i>h</i> symmetry. <b>1</b>_<b>H</b> is capable of releasing H₂ gas upon irradiation with sunlight, under mild thermal conditions (65 °C), or in the presence of acids at room temperature

Hydrido Copper Clusters Supported by Dithiocarbamates: Oxidative Hydride Removal and Neutron Diffraction Analysis of [Cu₇(H){S₂C(aza-15-crown-5)}₆]

Reactions of Cu­(I) salts with Na­(S₂CR) (R = N^<i>n</i>Pr₂, 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, [Cu₈(H)­{S₂CR}₆]­(PF₆) (R = N^<i>n</i>Pr₂, <b>1</b>_<b>H</b>; NEt₂, <b>2</b>_<b>H</b>; aza-15-crown-5, <b>3</b>_<b>H</b>). Further reactions of [Cu₈(H)­{S₂CR}₆]­(PF₆) with 1 equiv of (Bu₄N)­(BH₄) produced neutral heptanuclear copper clusters, [Cu₇(H)­{S₂CR}₆] (R = N^<i>n</i>Pr₂, <b>4</b>_<b>H</b>; NEt₂, <b>5</b>_<b>H</b>; aza-15-crown-5, <b>6</b>_<b>H</b>) and clusters <b>4</b>–<b>6</b> 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^I₈ clusters by adding 1 equiv of Cu^I salt to the neutral Cu₇ clusters in solution is observed. Intriguingly, the central hydride in [Cu₈(H)­{S₂CN^<i>n</i>Pr₂}₆]­(PF₆) can be oxidatively removed as H₂ by Ce­(NO₃)₆^2– to yield [Cu^II(S₂CN^<i>n</i>Pr₂)₂] exploiting the redox-tolerant nature of dithiocarbamates. Regeneration of hydride-centered octanuclear copper clusters from the [Cu^II(S₂CN^<i>n</i>Pr₂)₂] can be achieved by reaction with Cu­(I) ions and borohydride. The hydride release and regeneration of Cu^I₈ 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 H₂ via chemical means. All complexes have been fully characterized by ¹H NMR, FT-IR, UV–vis, and elemental analysis, and molecular structures of <b>1</b>_<b>H</b>, <b>2</b>_<b>H</b>, and <b>6</b>_<b>H</b> were clearly established by single-crystal X-ray diffraction. Both <b>1</b>_<b>H</b> and <b>2</b>_<b>H</b> exhibit a tetracapped tetrahedral Cu₈ skeleton, which is inscribed within a S₁₂ icosahedron constituted by six dialkyl dithiocarbamate ligands in a tetrametallic-tetraconnective (μ₂, μ₂) bonding mode. The copper framework of <b>6</b>_<b>H</b> is a tricapped distorted tetrahedron in which the four-coordinate hydride is demonstrated to occupy the central site by single crystal neutron diffraction. Compounds <b>1</b>–<b>3</b> 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 ³metal 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

A Nanospheric Polyhydrido Copper Cluster of Elongated Triangular Orthobicupola Array: Liberation of H₂ from Solar Energy

An unprecedented air-stable, nanospheric polyhydrido copper cluster, [Cu₂₀H₁₁(S₂P­(OⁱPr)₂)₉] (<b>1</b>_<b>H</b>), which is the first example of an elongated triangular orthobicupola array of Cu atoms having <i>C</i>_3<i>h</i> symmetry, was synthesized and characterized. Its composition was primarily determined by electrospray ionization mass spectrometry, and it was fully characterized by ¹H, ²H, and ³¹P NMR spectroscopy and single-crystal X-ray diffraction (XRD). The structure of complex <b>1</b>_<b>H</b> can be expressed in terms of a trigonal-bipyramidal [Cu₂H₅]^3– unit anchored within an elongated triangular orthobicupola containing 18 Cu atoms, which is further stabilized by 18 S atoms from nine dithiophosphate ligands and six capping hydrides. The positions of the 11 hydrides revealed by low temperature XRD were supported by a density functional theory investigation on the simplified model [Cu₂₀H₁₁(S₂PH₂)₉] with <i>C</i>_3<i>h</i> symmetry. <b>1</b>_<b>H</b> is capable of releasing H₂ gas upon irradiation with sunlight, under mild thermal conditions (65 °C), or in the presence of acids at room temperature

Shape Modulation of Octanuclear Cu(I) or Ag(I) Dichalcogeno Template Clusters with Respect to the Nature of their Encapsulated Anions: A Combined Theoretical and Experimental Investigation

M₈L₆ clusters (M = Cu­(I), Ag­(I); L = dichalcogeno ligand) are known for their ability to encapsulate various kinds of saturated atomic anions. Calculations on the models [M₈(E₂PH₂)₆]²⁺ (M = Cu­(I), Ag­(I); E = S, Se) and the ionic or neutral [M₈(X)­(E₂PH₂)₆]^<i>q</i> (X = H, F, Cl, Br, O, S, Se, N, P, C) indicate that the cubic M₈L₆ cage adapts its shape for maximizing the host–guest bonding interaction. The interplay between size, covalent and ionic bonding favors either a cubic, tetracapped tetrahedral, or bicapped octahedral structure of the metal framework. Whereas the large third- and fourth-row main group anions maintain the cubic shape, a distortion toward a tetracapped tetrahedral arrangement of the metals occurs in the case of hydride, fluoride, and oxide. The distortion is strong in the case of hydride, weak in the case of fluoride, and intermediate in the case of oxide. Density functional theory (DFT) calculations predict a bicapped octahedral architecture in the case of nitride and carbide. These computational results are supported by X-ray structures, including those of new fluorine- and oxygen-containing compounds. It is suggested that other oxygen-containing as well as so far unknown nitride-containing clusters should be feasible. For the first time, the dynamical behavior of the encapsulated hydride has been investigated by metadynamics simulations. Our results clearly demonstrate that the interconversion mechanism between two identical tetracapped tetrahedral configurations occurs through a succession of M-H bonds breaking and forming which present very low activation energies and which involve a rather large number of intermediate structures. This mechanism is full in accordance with ¹⁰⁹Ag and ¹H state NMR measurements