Copper Clusters Containing Hydrides in Trigonal Pyramidal Geometry

International audienceStructurally precise copper hydrides [CuH{SP(OPr)}(C≡CR)], R = Ph (1), CHF (2), and CHOMe (3), were first synthesized from the polyhydrido copper cluster [CuH{SP(OPr)}] with nine equivalents of terminal alkynes. Later, their isolated yields were significantly improved by direct synthesis from [Cu(CHCN)](PF), [NH][SP(OPr)], NaBH, and alkynes along with NEt in THF. 1, 2, and 3 were fully characterized by single-crystal X-ray diffraction, ESI-MS, and multinuclear NMR spectroscopy. All three clustershave 11 copper atoms, adopting 3,3,4,4,4-pentacapped trigonal prismatic geometry, with two hydrides inside the Cu cage, the position of which was ascertained by a single-crystal neutron diffraction structure of cluster 1 co-crystallized with a [Cu(H){SP(OPr)}] (4) cluster. Six dithiophosphate and three alkynyl ligands stabilize the CuH core in which the two hydrides adopt a trigonal pyramidal coordination mode. This coordination mode is so far unprecedented for hydride. The H NMR resonance frequency of the two hydrides appears at 4.8 ppm, a value further confirmed by H NMR spectroscopy for their deuteride derivatives [Cu(D){SP(OPr)}(C≡CR)]. A DFT investigation allows understanding the bonding within this new type of copper(I) hydrides

A heteroleptic fused bi-cuboctahedral cluster

International audienceA new dicationic cluster, [Cu21S2{(S2CNBu2)-Bu-n}(9)(C2Ph)(6)](2+), where the Cu21S2 kernel consists of two S@Cu-12 cuboctahedra sharing a triangular Cu-3 face is reported. Its waist part is bridged by three dithiocarbamate ligands, each in a hexaconnective, hexametallic (mu(3), mu(3)) coordination pattern, an unprecedented feature in Cu nanocluster chemistry

Unusual core engineering on a copper hydride nanoball

International audienceA neutral polyhydrido copper cluster, [Cu27H15{(S2CNBu2)-Bu-n}(12)] (abbreviated as [Cu27H15]), was prepared by the reaction of dithiocarbamates (dtc), Cu(i) salts and NaBH4. The isolated cluster provides insights into core engineering, demonstrating its novel ability to reversibly add or remove one copper atom from the cluster core. Single-crystal X-ray analysis reveals that the new core-shell structure exhibits a Cu-24 rhombicuboctahedral outer cage and an inner Cu-3 triangular kernel. The two core-shell clusters, [Cu27H15{(S2CNBu2)-Bu-n}(12)] and previously published [Cu28H15((S2CNBu2)-Bu-n)(12)](+) (abbreviated as [Cu28H15](+)), are only differentiated by one copper atom in their inner core. Importantly, we demonstrate core engineering with the controllable reversible transition between an irregular Cu-4 tetrahedron and a Cu-3 triangle, whilst maintaining their outer Cu-24 shell intact. The 15 hydride atoms in [Cu27H15], coordinated in three different modes, are co-incident with the hydride positions in [Cu28H15](+). The degradation of [Cu27H15] in solution or the addition of one eq. of Cu(i) ions leads to the conversion of [Cu27H15] into [Cu28H15](+), while the reverse transformation can be achieved by the addition of either formic acid or a reducing agent to [Cu28H15](+). A dicationic species was observed in the ESI mass spectrum, and the composition is formulated as [Cu56H30((S2CNBu2)-Bu-n)(24)](2+), a dimer of [Cu27H15((S2CNBu2)-Bu-n)(12) + Cu+](2)(2+). The dimeric species was further explored by DFT calculations, suggesting that the lowest energy structure consists of a [Cu28H15](+) and a [Cu27H15] cluster connected through one Cu+ atom bridge. As a result, [Cu27H15] is considered an intermediate species in the formation of the more stable [Cu28H15](+) nanoball

Structural alterations on copper cages containing hydrides coordinated to the central Pd(0)

International audienceA crucial component of nanocluster (NC) chemistry is the design and control of complex molecular architectures with atomic precision. Herein, we report the synthesis and structure of [PdH2Cu11{S2P(OiPr)2}6(Ctriple bondCPh)3] (PdH2Cu11), confirmed by single-crystal X-ray diffraction (SC-XRD), NMR spectroscopy, elemental analysis, and electrospray ionization mass spectrometry (ESI-MS). PdH2Cu11 is obtained from the reaction of a parent cluster [PdH2Cu14{S2P(OiPr)2}6(Ctriple bondCPh)6] (PdH2Cu14) with trifluoroacetic acid (TFA). Importantly the addition of TFA does not result in the loss of the hydride atoms located at the kernel, and H-Pd-H motif is retained. The molecular structure of PdH2Cu11 consists of a distorted 3,3,4,4,4-pentacapped trigonal prism Cu11 cage encapsulating a quasi-linear H-Pd-H unit, stabilized by dithiophosphate and alkynyl ligands. DFT calculations suggest an ionic inclusion complex of the type [{PdH2}2−]@[{Cu11{S2P(OiPr)2}6(Ctriple bondCPh)3}2+] and confirm the hydride positions. A non-covalent inter-cluster interaction results in the unique formation of a unique honeycomb crystal lattice. Overall, this work broadens and deepens the understanding of Pd-Cu hydride alloy nanoclusters

Reactivities of Interstitial Hydrides in a Cu-11 Template: En Route to Bimetallic Clusters

International audienceIn sharp contrast to surface hydrides, reactivities of interstitial hydrides are difficult to explore. When treated with a metal ion (Cu , Ag , and Au ), the stable Cu dihydride template [Cu H {S P(O Pr) } (C≡CPh) ] (H Cu ) generates surprisingly three very different compounds, namely [CuH Cu {S P(O Pr) } (C≡CPh) ] (1), [AgH Cu {S P(O Pr) } ((C≡CPh) ] (2), and [AuCu {S P(O Pr) } (C≡CPh) Cl] (3). Compounds 1 and 2 are both M species and maintain the same number of hydride ligands as their H Cu precursor. Neutron diffraction revealed the first time a trigonal-pyramidal hydride coordination mode in the AgCu environment of 2. 3 has no hydride and exhibits a mixed-valent [AuCu ] metal core, making it a two-electron superatom

Isolation and Structural Elucidation of 15-Nuclear Copper Dihydride Clusters: An Intermediate in the Formation of a Two-Electron Copper Superatom

International audienceHighly reactive copper-dihydride clusters, [Cu (H) (S CNR ) (C Ph) ](PF ) {R = Bu (1 ), Pr (2 ), Bu (3 )}, are isolated during the reaction of [Cu H {S CN Bu } ](PF ) with ten equivalents of phenylacetylene. They are found to be intermediates in the formation of the earlier reported two-electron superatom [Cu (S CNR ) (C Ph) ] . Better yields are obtained by reacting dithiocarbamate sodium salts, [Cu(CH CN) ](PF ), BH and phenylacetylene. The presence of two hydrides in the isolated clusters is confirmed by the synthesis and characterization of its deuteride analogue [Cu (D) (S CNR ) (C Ph) ] , and a single-crystal neutron structure of 2 . Structural characterization of 1 reveals a new bicapped icosahedral copper(I) cage encapsulating a linear copper dihydride (CuH ) unit. Reaction of 3 with Au(I) salts yields a highly luminescent [AuCu (S CN Bu ) (C Ph) ] cluster

Synthesis and structural characterization of inverse-coordination clusters from a two-electron superatomic copper nanocluster

International audienceWe have synthesized and structurally characterized a series of centred cuboctahedral copper clusters, namely [Cu{SCNR}{C[triple bond, length as m-dash]CR'}](PF), (where : R = Bu, R' = COMe; : R = Bu, R' = COEt; : R = Pr, R' = COEt; : R = Pr, R' = 3,5-(CF)CH); [Cu(μ-S){SCNR}{C[triple bond, length as m-dash]CR'}], ; [Cu(μ-Cl){SCNR}{C[triple bond, length as m-dash]CR'}](PF), (where : R = Bu, R' = Ph); [Cu(μ-Br){SCN Bu}{C[triple bond, length as m-dash]CPh}](PF), ; and [Cu(μ-Cl)(μ-Cl){SCN Bu}{C[triple bond, length as m-dash]CCOMe}]. Cluster is the first structurally characterized copper cluster having a Cu centered cuboctahedral arrangement, a miniature of the bulk copper structure. Furthermore, the partial Cu(0) character in the 2-electron superatoms was confirmed by XANES. Inverse coordination clusters are the first examples of copper clusters containing main group elements (Cl, Br, S) with a hyper-coordination number, twelve. A combined theoretical and experimental study was performed, which shows that the central copper (formally Cu) in nanoclusters can be replaced by chalcogen/halogen atoms, resulting in the formation of clusters which show enhanced luminescence properties and increase in the ionic component of the host-guest interaction as Br ≈ Cl > S > Cu, which is consistent with the Cu-X Wiberg indices. The new compounds have been characterized by ESI-MS, H, C NMR, IR, UV-visible, emission spectroscopy, and the structures , , and were established by X-ray diffraction analysis

Hydride-containing 2-Electron Pd/Cu Superatoms as Catalysts for Efficient Electrochemical Hydrogen Evolution

International audienceThe first hydride-containing 2-electron palladium/copper alloys, [PdHCu11{S2P(O i Pr)2}6(C≡CPh)4] (PdHCu11) and [PdHCu12{S2P(O i Pr)2}5{S2PO(O i Pr)} (C≡CPh)4] (PdHCu12), are synthesized from the reaction of [PdH2Cu14{S2P(O i Pr)2}6(C≡CPh)6] (PdH2Cu14) with trifluoroacetic acid (TFA). X-ray diffraction reveals that the PdHCu11 and PdHCu12 kernels consist of a central PdH unit encapsulated within a vertex-missing Cu11 cuboctahedron and complete Cu12 cuboctahedron, respectively. DFT calculations indicate that both PdHCu11 and PdHCu12can be considered as axially-distorted 2-electron superatoms. PdHCu11 shows excellent HER activity, unprecedented within metal nanoclusters, with an onset potential of -0.05 V (at 10 mA cm-2), a Tafel slope of 40 mV dec-1, and consistent HER activity during 1000 cycles. Our study suggests that the accessible central Pd site is the key to HER activity and may provide guidelines for correlating catalyst structures and HER activity

Synthesis of Bimetallic Copper-Rich Nanoclusters Encapsulating a Linear Palladium Dihydride Unit

International audienceThe structurally precise Cu-rich hydride nanoclusters [PdCu H (dtc/dtp) (C≡CPh) ] (dtc: di-butyldithiocarbamate (1); dtp: di-isopropyl dithiophosphate (2)) were synthesized from the reaction of polyhydrido copper clusters [Cu H (S CN Bu ) ] or [Cu H {S P(O Pr) } ] with phenyl acetylene in the presence of Pd(PPh ) Cl . Their structures and compositions were determined by single-crystal X-ray diffraction and the results supported by ESI-mass spectrometry. Hydride positions in 1 were confirmed by single-crystal neutron diffraction. Each hydride is connected to one Pd and four Cu atoms in slightly distorted trigonalbipyramidal geometry. The anatomies of clusters 1 and 2 are very similar and DFT calculations allow rationalizing the interactions between the encapsulated [PdH ] unit and its Cu bicapped icosahedral cage. As a result, Pd has the highest coordination number (14) so far recorded

Synthesis and Luminescence Properties of Two-Electron Bimetallic Cu-Ag and Cu-Au Nanoclusters via Copper Hydride Precursors

International audienceThe synthesis, structural characteristics, and photophysical properties of luminescent Cu-rich bimetallic superatomic clusters [Au@Cu-12((S2CNPr2)-Pr-n)(6)(C CPh)(4)](+) (1a(+)), [Au@Cu-12{S2P(OR)(2)}(6)(C CPh)(4)](+) (2(+)), (2a(+) = Pr-i; 2b(+) = Pr-n), [Au@Cu-12{S2P(C2H4Ph)(2)}(6)(C CPh)(4)](+) (2c(+)), and [Ag@Cu-12{S2P((OPr)-Pr-n)(2)}(6)(C CPh)(4)](+) (3(+)) were studied. Compositionally uniform clusters 1(+)-3(+) were isolated from the reaction of dithiolato-stabilized, polyhydrido copper clusters with phenylacetylene in the presence of heterometal salts. By using X-ray diffraction, the structures of 1a(+), 2a(+), 2b(+), and 3(+) were able to be determined. ESI-mass spectrometry and elemental analysis confirmed their compositions and purity. The structural characteristics of these clusters are similar with respect to displaying gold (or silver)-centered Cu-12 cuboctahedra surrounded by six dithiocarbamate/dithiophosph(in)ate and four alkynyl ligands. The doping of Au and Ag atoms into the polyhydrido copper nanoclusters significantly enhances their PL quantum yields from Ag@Cu-12 (0.58%) to Au@Cu-12 (55%) at ambient temperature in solution. In addition, the electrochemical properties of the new alloys were investigated by cyclic voltammetry