The structurally precise Cu‐rich hydride nanoclusters [PdCu14H2(dtc/dtp)6(C≡CPh)6] (dtc: di‐butyldithiocarbamate (1); dtp: di‐isopropyl dithiophosphate (2)) were synthesized from the reaction of polyhydrido copper clusters [Cu28H15(S2CNnBu2)12]+ or [Cu20H11{S2P(OiPr)2}9] with phenyl acetylene in the presence of Pd(PPh3)2Cl2. 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 Pd0 and four CuI 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 [PdH2]2− unit and its Cu14 bicapped icosahedral cage. As a result, Pd has the highest coordination number (14) so far recorded.

Cuboctahedral copper clusters containing a twelve-coordinated main group element (Cl, Br, S) at the center have been synthesized and characterized.

Highly reactive copper‐dihydride clusters, [Cu15(H)2(S2CNR2)6(C2Ph)6](PF6) {R = nBu (1H), nPr (2H), iBu (3H)}, are isolated during the reaction of [Cu28H15{S2CNnBu2}12](PF6) with ten equivalents of phenylacetylene. They are found to be intermediates in the formation of the earlier reported two‐electron superatom [Cu13(S2CNR2)6(C2Ph)4]+. Better yields are obtained by reacting dithiocarbamate sodium salts, [Cu(CH3CN)4](PF6), BH4− and phenylacetylene. The presence of two hydrides in the isolated clusters is confirmed by the synthesis and characterization of its deuteride analogue [Cu15(D)2(S2CNR2)6(C2Ph)6]+, and a single‐crystal neutron structure of 2H. Structural characterization of 1H reveals a new bicapped icosahedral copper(I) cage encapsulating a linear copper dihydride (CuH2)− unit. Reaction of 3H with Au(I) salts yields a highly luminescent [AuCu12(S2CNiBu2)6(C2Ph)4]+ cluster.

Structurally precise copper hydrides [Cu 11 H 2 {S 2 P(O i Pr) 2 } 6 (C≡CR) 3 ], (R= Ph (1), C 6 H 4 F (2) and C 6 H 4 OMe (3) were first synthesized from the polyhydrido copper cluster [Cu 20 H 11 {S 2 P(O i Pr) 2 } 9 ] with nine equiv. of terminal alkynes. Later their isolated yields were significantly improved by direct synthesis from [Cu(CH 3 CN) 4 ](PF 6), [NH 4 ][S 2 P(O i Pr) 2 ], NaBH 4 , and alkynes along with NEt 3 in THF. 1, 2, and 3 were fully characterized by single-crystal X-ray diffraction, ESI-MS and multinuclear NMR spectroscopy. All three clusters have eleven copper atoms adopting 3, 3, 4, 4, 4-pentaccaped trigonal prismatic geometry, with two hydrides inside the Cu 11 cage, the position of which being ascertained by a single-crystal neutron diffraction structure of cluster 1 co-crystallized with a [Cu 7 (H){S 2 P(O i Pr) 2 } 6 ], 4 cluster. Six dithiophosphate and three alkynyl ligands stabilize the Cu 11 H 2 core in which the two hydrides adopt a trigonal pyramidal coordination mode. This coordination mode is so far unprecedented for hydride. The 1 H NMR resonance frequency of the two hydrides appears at 4.8 ppm, a value further confirmed 1 A c c e p t e d m a n u s c r i p t by 2 H NMR spectroscopy for their deuteride derivatives [Cu 11 (D) 2 {S 2 P(O i Pr) 2 } 6 (C≡CR) 3 ]. A DFT investigation allows understanding the bonding within this new type of copper(I) hydrides.

The first hydride-containing 2-electron palladium/copper alloys, [PdHCu 11 {S 2 P(O i Pr) 2 } 6 (C�CPh) 4 ] (PdHCu 11 ) and [PdHCu 12 {S 2 P(O i Pr) 2 } 5 {S 2 PO(O i Pr)} (C�CPh) 4 ] (PdHCu 12 ), are synthesized from the reaction of [PdH 2 Cu 14 {S 2 P(O i Pr) 2 } 6 (C�CPh) 6 ] (PdH 2 Cu 14 ) with trifluoroacetic acid (TFA). X-ray diffraction reveals that the PdHCu 11 and PdHCu 12 kernels consist of a central PdH unit encapsulated within a vertex-missing Cu 11 cuboctahedron and complete Cu 12 cuboctahedron, respectively. DFT calculations indicate that both PdHCu 11and PdHCu 12 can be considered as axially-distorted 2electron superatoms. PdHCu 11 shows excellent HER activity, unprecedented within metal nanoclusters, with an onset potential of À 0.05 V (at 10 mA cm À 2 ), a Tafel slope of 40 mV dec À 1 , and consistent HER activity during 1000 cycles in 0.5 M H 2 SO 4 . 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.

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Atomically precise Cu-rich bimetallic superatom clusters have been synthesized by adopting a galvanic exchange strategy. [Cu@Cu (S CN Bu ) (C≡CPh) ][CuCl ] (1) was used as a template to generate compositionally uniform clusters [M@Cu (S CN Bu ) (C≡CPh) ][CuCl ], where M=Ag (2), Au (3). Structures of 1, 2 and 3 were determined by single crystal X-ray diffraction and the results were supported by ESI-MS. The anatomies of clusters 1-3 are very similar, with a centred cuboctahedral cationic core that is surrounded by six di-butyldithiocarbamate (dtc) and four phenylacetylide ligands. The doped Ag and Au atoms were found to preferentially occupy the centre of the 13-atom cuboctahedral core. Experimental and theoretical analyses of the synthesized clusters revealed that both Ag and Au doping result in significant changes in cluster stability, optical characteristics and enhancement in luminescence properties.

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