An All-Metal Aromatic Sandwich Complex [Sb₃Au₃Sb₃]^3–

Abstract

A sandwich complex, as exemplified by ferrocene in the 1950s, usually refers to one metal center bound by two arene ligands. The subject has subsequently been extended to carbon-free aromatic ligands and multiple-metal-atom "monolayered" center, but not to an all-metal species. Here, we describe the synthesis of an unprecedented all-metal aromatic sandwich complex, [Sb3Au3Sb3](3-), which was isolated as K([2.2.2]crypt)(+) salt and identified by single-crystal X-ray diffraction. Quantum chemical calculations indicate that intramolecular electron transfers for the three metallic layers (Sb → Au donation and Sb ← Au back-donation) markedly redistribute the valence electrons from the cyclo-Sb3 ligands and Au3 interlayer to the Au-Sb bonds, which hold the complex together via σ bonding. Each cyclo-Sb3 possesses aromaticity with delocalized three-center three-electron (3c-3e) π bonds, which are essentially equivalent to a 3c-4e ππ* triplet system, following the reversed 4n Hückel rule for aromaticity in a triplet state.

Chemical Bonding and σ-Aromaticity in Charged Molecular Alloys: [Pd2As14]4− and [Au2Sb14]4− Clusters

“…However, the structural description on the basis of bond distances, as outlined in the previous section, allows simplification of the task, because there exist clearly 16 As-As and 8 Pd-As single bonds in 1 , which consume 48 electrons. Furthermore, according to our recent work on [Sb 3 Au 3 Sb 3 ] 3− all-metal sandwich 36, 37 , the As 4s 2 electrons in 1 are anticipated to well behave as lone-pairs (14 of them, consuming 28 electrons). The above-mentioned single bonds and lone-pairs use 76 electrons out of 94 in 1 , whose corresponding CMOs are depicted in Fig.…”

“…In the past years, we have been interested in exploring the structural, electronic, and bonding properties of gas-phase clusters 23–27 and synthetic cluster compounds 36–38 . In the present contribution, we shall report on a quantum chemical study on the structure and bonding of a “charged molecular alloy” cluster: D 2 h [Pd 2 As 14 ] 4− ( 1 ).…”

Computational insights into the concomitant changes of hollow interior evolution in [SbnAunSbn]m (n=3, 4, 5, 6; m= -3, -2, -1, -2) complex

“…[19][20][21] Hence, All structures of [Sb n Au n Sb n ] m (n= 3, 4, 5, 6; m= -3, -2, -1, -2) are optimized by density functional theory (DFT) at PBE1PBE/def2-TZVP 26,27 using the Gaussian 09 program. 28 Frequency computations are conducted to characterize the nature of all stationary points at the same level.…”

“…31,32 The NICS values are calculated at the same level of theory using gauge-including atomic orbital (GIAO) method by G09 program. And the parameters for a pyridine (Py) solvent are used in the COSMO calculations as Py is used as a solvent for recrystallization in the experimental synthesis 19 and is also the most common solvent used in the lab studies for comparison.…”

All-metal binuclear sandwich complexes Al4Ti2Al4: High capacity hydrogen storage through multicenter bonds

“…The pioneering experimental characterization of the all-mental aromatic unit Al 4 2À in the bimetallic molecules MAl 4 À (M ¼ Li, Na, Cu) by Li et al, in 2001 inspires many researchers to study the all-metal sandwich-type complexes [6]. It is just recently, a new cluster anion, [Sb 3 Au 3 Sb 3 ] 3À , in which an Au 3 ring is sandwiched by two cyclo-Sb 3 has been synthesized and characterized [7]. The Al 4 2À unit was found to be square planar and to possess two delocalized л electrons (thus satisfying the 4n þ 2 electron counting rule for aromaticity).…”