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Gold does not react with H2 to form bulk hydrides. Here we report the synthesis and characterization of a gold nanohydride protected by diphosphine ligands, [Au22H4(dppo)6]2+ [dppo=1,8‐bis(diphenylphosphino)octane]. The Au22 core consists of two Au11 units bonded by eight Au atoms not coordinated by the diphosphine ligands. The four H atoms are found to bridge the eight uncoordinated Au atoms at the interface. Each Au11 unit can be viewed as a tetravalent superatom forming four delocalized Au‐H‐Au bonds, similar to the quadruple bond first discovered in the [Re2Cl8]2− inorganic cluster. The [Au22H4(dppo)6]2+ nanohydride is found to lose H atoms over an extended time via H evolution (H2), proton (H+) and hydride (H−) releases. This complete repertoire of H‐related transformations suggests that the [Au22H4(dppo)6]2+ nanohydride is a versatile model catalyst for understanding the mechanisms of chemical reactions involving hydrogen on the surface of gold nanoparticles. [ABSTRACT FROM AUTHOR]

Multiple bonds between boron and transition metals are known in many borylene (:BR) complexes via metal dπ→BR back‐donation, despite the electron deficiency of boron. An electron‐precise metal–boron triple bond was first observed in BiB2O− [Bi≡B−B≡O]− in which both boron atoms can be viewed as sp‐hybridized and the [B−BO]− fragment is isoelectronic to a carbyne (CR). To search for the first electron‐precise transition‐metal‐boron triple‐bond species, we have produced IrB2O− and ReB2O− and investigated them by photoelectron spectroscopy and quantum‐chemical calculations. The results allow to elucidate the structures and bonding in the two clusters. We find IrB2O− has a closed‐shell bent structure (Cs, 1A′) with BO− coordinated to an Ir≡B unit, (−OB)Ir≡B, whereas ReB2O− is linear (C∞v, 3Σ−) with an electron‐precise Re≡B triple bond, [Re≡B−B≡O]−. The results suggest the intriguing possibility of synthesizing compounds with electron‐precise M≡B triple bonds analogous to classical carbyne systems. [ABSTRACT FROM AUTHOR]

In a high‐resolution photoelectron imaging and theoretical study of the IrB3− cluster, two isomers were observed experimentally with electron affinities (EAs) of 1.3147(8) and 1.937(4) eV. Quantum calculations revealed two nearly degenerate isomers competing for the global minimum, both with a B3 ring coordinated with the Ir atom. The isomer with the higher EA consists of a B3 ring with a bridge‐bonded Ir atom (Cs, 2A′), and the second isomer features a tetrahedral structure (C3v, 2A1). The neutral tetrahedral structure was predicted to be considerably more stable than all other isomers. Chemical bonding analysis showed that the neutral C3v isomer involves significant covalent Ir−B bonding and weak ionic bonding with charge transfer from B3 to Ir, and can be viewed as an Ir–(η3‐B3+) complex. This study provides the first example of a boron‐to‐metal charge‐transfer complex and evidence of a π‐aromatic B3+ ring coordinated to a transition metal. [ABSTRACT FROM AUTHOR]

A facile synthesis of heavy alkali metal octahydrotriborates (MB3H8; M=K, Rb, and Cs) has been developed. It is simply based on reactions of the pure alkali metals with THF⋅BH3, does not require the use of electron carriers or the addition of other reaction media such as mercury, silica gel, or inert salts as for previous procedures, and delivers the desired products at room temperature in very high yields. However, no reactions were observed when pure Li or Na was used. The reaction mechanisms for the heavy alkali metals were investigated both experimentally and computationally. The low sublimation energies of K, Rb, and Cs were found to be key for initiation of the reactions. The syntheses can be carried out at room temperature because all of the elementary reaction steps have low energy barriers, whereas reactions of LiBH4/NaBH4 with THF⋅BH3 have to be carried out under reflux. The high stability and solubility of KB3H8 were examined, and a crystal structure thereof was obtained for the first time. Sublime reactivity: Unsolvated MB3H8 (M=K, Rb, and Cs) salts were prepared by reactions of the respective pure alkali metals with THF⋅BH3 in high yield at room temperature, and the structure of unsolvated KB3H8 was elucidated. The proposed reaction mechanisms are based on experimental and theoretical results. It was found that the physical properties of the alkali metals play a crucial role. [ABSTRACT FROM AUTHOR]

Despite its electron deficiency, boron is versatile in forming multiple bonds. Transition-metal-boron double bonding is known, but boron-metal triple bonds have been elusive. Two bismuth boron cluster anions, BiB2O− and Bi2B−, containing triple and double B−Bi bonds are presented. The BiB2O− and Bi2B− clusters are produced by laser vaporization of a mixed B/Bi target and characterized by photoelectron spectroscopy and ab initio calculations. Well-resolved photoelectron spectra are obtained and interpreted with the help of ab initio calculations, which show that both species are linear. Chemical bonding analyses reveal that Bi forms triple and double bonds with boron in BiB2O− ([Bi≡B−B≡O]−) and Bi2B− ([Bi=B=Bi]−), respectively. The Bi−B double and triple bond strengths are calculated to be 3.21 and 4.70 eV, respectively. This is the first experimental observation of Bi−B double and triple bonds, opening the door to design main-group metal-boron complexes with multiple bonding. [ABSTRACT FROM AUTHOR]

The structure and bonding of a Pr-doped boron cluster (PrB7−) are investigated using photoelectron spectroscopy and quantum chemistry. The adiabatic electron detachment energy of PrB7− is found to be low [1.47(8) eV]. A large energy gap is observed between the first and second detachment features, indicating a highly stable neutral PrB7. Global minimum searches and comparison between experiment and theory show that PrB7− has a half-sandwich structure with C6v symmetry. Chemical bonding analyses show that PrB7− can be viewed as a PrII[η7-B73−] complex with three unpaired electrons, corresponding to a Pr (4f26s1) open-shell configuration. Upon detachment of the 6s electron, the neutral PrB7 cluster is a highly stable PrIII[η7-B73−] complex with Pr in its favorite +3 oxidation state. The B73− ligand is found to be highly stable and doubly aromatic with six delocalized π and six delocalized σ electrons and should exist for a series of lanthanide MIII[η7-B73−] complexes. [ABSTRACT FROM AUTHOR]

Monolayer-boron (borophene) has been predicted with various atomic arrangements consisting of a triangular boron lattice with hexagonal vacancies. Its viability was confirmed by the observation of a planar hexagonal B36 cluster with a central six-membered ring. Here we report a planar boron cluster doped with a transition-metal atom in the boron network (CoB18−), suggesting the prospect of forming stable hetero-borophenes. The CoB18− cluster was characterized by photoelectron spectroscopy and quantum chemistry calculations, showing that its most stable structure is planar with the Co atom as an integral part of a triangular boron lattice. Chemical bonding analyses show that the planar CoB18− is aromatic with ten π-electrons and the Co atom has strong covalent interactions with the surrounding boron atoms. The current result suggests that transition metals can be doped into the planes of borophenes to create metallo-borophenes, opening vast opportunities to design hetero-borophenes with tunable chemical, magnetic, and optical properties. [ABSTRACT FROM AUTHOR]

Antiaromaticity, as introduced in 1965, usually refers to monocyclic systems with 4 n π electrons. This concept was extended to all-metal molecules after the observation of Li3Al4− in the gas phase. However, the solid-phase counterparts have not been documented to date. Herein, we describe a series of all-metal antiaromatic anions, [Ln( η4-Sb4)3]3−(Ln=La, Y, Ho, Er, Lu), which were isolated as the K([2.2.2]crypt) salts and identified by single-crystal X-ray diffraction. Based on the results obtained from the chemical bonding analysis, multicenter indices, and the electron-counting rule, we conclude that the core [Ln( η4-Sb4)3]3− fragment of the crystal has three locally π-antiaromatic Sb4 fragments. This complex represents the first locally π-antiaromatic all-metal system in the solid state, which is stabilized by interactions of the three π-antiaromatic units with the central metal atom. [ABSTRACT FROM AUTHOR]

Chirality is vital in chemistry. Its importance in atomic clusters has been recognized since the discovery of the first chiral fullerene, the D2 symmetric C76. A number of gold clusters have been found to be chiral, raising the possibility to use them as asymmetric catalysts. The discovery of clusters with enantiomeric structures is essential to design new chiral materials with tailored chemical and physical properties. Herein we report the first inherently chiral boron cluster of [B30]− in a joint photoelectron spectroscopy and theoretical study. The most stable structure of [B30]− is found to be quasiplanar with a hexagonal hole. Interestingly, a pair of enantiomers arising from different positions of the hexagonal hole are found to be degenerate in our global minimum searches and both should co-exist experimentally because they have identical electronic structures and give rise to identical simulated photoelectron spectra. [ABSTRACT FROM AUTHOR]

Molecules with large enough dipole moments can bind an electron by the dipole field, which has little effect on the molecular core. A molecular anion can be excited to a dipole-bound state, which can autodetach by vibronic coupling. Autodetachment spectroscopy of a complex anion cooled in a cryogenic ion trap is reported. Vibrational spectroscopy of the dehydrogenated uracil radical is obtained by a dipole-bound state with partial rotational resolution. Fundamental frequencies for 21 vibrational modes of the uracil radical are reported. The electron affinity of the uracil radical is measured accurately to be 3.4810±0.0006 eV and the binding energy of the dipole-bound state is measured to be 146±5 cm−1. The rotational temperature of the trapped uracil anion is evaluated to be 35 K. [ABSTRACT FROM AUTHOR]

It has been a long-sought goal in cluster science to discover stable atomic clusters as building blocks for cluster-assembled nanomaterials, as exemplified by the fullerenes and their subsequent bulk syntheses., Clusters have also been considered as models to understand bulk properties, providing a bridge between molecular and solid-state chemistry. Because of its electron deficiency, boron is an interesting element with unusual polymorphism. While bulk boron is known to be dominated by the three-dimensional (3D) B12 icosahedral motifs, new forms of elemental boron are continuing to be discovered. In contrast to the 3D cages commonly found in bulk boron, in the gas phase two-dimensional (2D) boron clusters are prevalent.- The unusual planar boron clusters have been suggested as potential new bulking blocks or ligands in chemistry. Herein we report a joint experimental and theoretical study on the [Ta2B6]− and [Ta2B6] clusters. We found that the most stable structures of both the neutral and anion are D6 h bipyramidal, similar to the recently discovered MB6M structural motif in the Ti7Rh4Ir2B8 solid compound. [ABSTRACT FROM AUTHOR]