Synthesis of a Trigold Monocation: An Isolobal Analogue of [H₃]⁺

Abstract

The ion [H 3 ] + represents a classic case in molecular orbital theory, the simplest three-center, two-electron bond. [1] The proton affinity of dihydrogen in the gas phase, at 4.4 eV, [2] is nearly equal to the bond enthalpy of H 2 itself. [3] The [H 3 ] + ion has been studied spectroscopically in the laboratory; [4] it has been detected in planetary atmospheres, [5a] and is notably abundant in interstellar space. [5b] The concept of isolobality has been used extensively to draw analogies between [LAu] + and [H] + , [6] and after the discovery of isolable [(LAu) 2 H] + complexes, [7,8] we became interested in the synthesis of an allgold analogue of [H 3 ] + .Complexes of gold(I) with atoms such as oxygen and the heavier chalcogens, nitrogen, and carbon, often exhibit weak but important aurophilic interactions between the d 10 metal centers. [9] Multicenter covalent bonding is observed in formally mixed-valent gold(I)/gold(0) clusters. [10] These include edge-sharing bitetrahedral clusters of the general formula [(LAu) 6 ] 2+ , [11] and tetrahedral clusters of the formula [(LAu) 4 ] 2+ . [12] Clusters such as [(LAu) 6 ] 2+ , (L 6 Au 8 ) 2+ , and [(LAu) 4 ] 2+ , have been synthesized by the reduction of phosphine-supported m 3 -oxo or m 3 -imido cations with carbon monoxide. [13] Whereas gold(II) dimers form covalent goldgold bonds through the interaction of half-filled d-orbitals, [14] the gold-gold bonding in mixed-valent gold(I)/gold(0) clusters [(LAu) n ] x+ arises to an important extent from symmetryadapted combinations of partially filled gold 6 s orbitals. [10b] The interaction of small gold clusters and nanoparticles with O 2 has been studied as a key step in aerobic oxidation catalysis. [15] The [Au 3 ] + -catalyzed oxidation of CO has been studied theoretically, [16] and [Au 3 ] + in the gas phase has been shown to mediate the oxidation of CO by N 2 O. [17] Mass spectrometry studies suggest that a transient [L 2 Au 3 ] + ion, where L 2 is a bridging bisphosphine, undergoes oxidative addition with aryl iodides. [18] Cluster complexes featuring the cyclo-Au 3 moiety bonded to tungsten [19] or to main-group elements [20] are known, as are triangular [Au 2 M] clusters. [21] We now report the characterization of a stable [(LAu) 3 ] + complex, where L is the N-heterocyclic carbene (NHC) 1,3bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IDipp). Density functional theory (DFT) lends insight into the bonding among gold centers. Preliminary studies demonstrate sluggish reactivity with oxygen-atom-transfer agents, but facile reactivity with soft electrophiles.Initially, we planned to obtain [(LAu) 3 ] + through the reduction of a corresponding m 3 -oxo complex [(LAu) 3 O] + . A wide range of phosphorus-based donor ligands support complexes of this type. [22] Our efforts to obtain an analogous NHC-supported species by the established routes gave rise to mixtures of products, including the hydroxide-bridged digold cation [(LAu) 2 OH] + . [23] Reasoning that the formation of strong silicon-heteroatom bonds co...

A grand unified model for liganded gold clusters

“…Moreover, from an experimental perspective, the Au 3 core of crystallized [Au 3 (IDipp) 3 ] 1+ [IDipp=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene] (ref. 5) and the Au 4 core of [Au 4 (PR 3 ) 4 ] 2+ (ref. 6) (Supplementary Table 2) are essentially the same as the elementary blocks Au 3 (2 e ) and Au 4 (2 e ), respectively, supporting the high stabilities of the Au 3 (2 e ) and Au 4 (2 e ).…”

“…A grand challenge to scientists in this field, however, is the precise determination of atomic structures of liganded gold clusters. To date, atomic structures of tens of liganded gold clusters have been determined via X-ray crystallography56789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263. Nevertheless, these revelations appear serendipitous as the structural determination largely hinges on availability of single crystals for the liganded gold clusters.…”

Die σ‐aromatischen Cluster [Zn3]+ und [Zn2Cu] – kleinste molekulare Bausteine für Messing

“…[4] 2012 wurde der ligandenstabilisierte Goldcluster [(LAu) 3 ] + (L = 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-yliden) isoliert (Abbildung 1). [5] + (Ar = C 6 H 4 F); [7] 4 ]w eist eine Cu-ZnBindungslänge von 2.498(2) a uf (gegenüber der in 2 5% länger). [14] Der durchschnittliche Zn-Cp* Zentroid -Abstand ist in 1 deutlich kürzer ( [19] in Verbindung mit der D3-Methode für Dispersionswechselwirkungen von Grimme et al [20] auf dem BP86(D3)/TZVPPNiveau berechnet.…”

Peculiar All‐Metal σ‐Aromaticity of the [Au2Sb16]4− Anion in the Solid State

“…[5] Thea romaticity/ antiaromaticity concept was also extended to bare metal clusters found in the gas phase. [12][13][14] Thus far,w ea re not aware of any solidstate compounds containing two all-metal s-aromatic fragments involving six delocalized electrons each. [7] Modern developments on aromaticity in various aromatic/antiaromatic chemical species composed of main-group elements and transition metals have been extensively reviewed elsewhere.…”

“…[6] Fort he first time,t he saromaticity concept was shown to be applicable to small alkali metal and alkaline earth metal clusters. Hence,the 6s-electron aromatic fragments found in the [Au 2 Sb 16 ] 4À cluster in this study expand the family of storable aromatic metal clusters thus solidifying usefulness of the s-aromaticity concept in the solid state.Thet itle complex [Au 2 Sb 16 ] 4À (1), crystallizes in the form of [K([2.2.2]crypt)] 4 ·1·4 en ( Figure S1 and Table S1), was isolated from an ethylenediamine (en) solution of K 3 Sb 7 , Au(PPh 3 ) Ph,and 4,7,13,16,21,hexacosane ([2.2.2]crypt;e xperimental details can be found in the Supporting Information). [8][9][10][11] Fora ll all-metal aromatic fragments that have been synthesized in the solid state up to date,t here were only two delocalized electrons responsible for the s-aromaticity of the compounds,asexemplified by the cases of Pd 3 + ,Au 3 + ,and TiSn 2 clusters.…”