Inorganic fullerene clusters have attracted widespread attention due to their highly symmetrical geometric structures and intrinsic electronic properties. However, cage-like clusters composed of heavy metal elements with high symmetry are rarely reported, and their synthesis is also highly challenging. In this study, we present the synthesis of a [K2(Bi@Pd12@Bi20)]4- cluster that incorporates a {Bi20} cage with pseudo-Ih symmetry, making it the largest main group metal cluster compound composed of the bismuth element to date. Magnetic characterization and theoretical calculations suggest that the spin state of the overall cluster is a quartet. Quantum chemical calculations reveal that the [Bi20]3- cluster has a similar electronic configuration to C606- and the [Bi@Pd12@Bi20]6- cluster exhibits a unique open-shell aromatic character.
We report here the synthesis and characterization of two endohedral Zintl-ion clusters, [Fe4Sn18]4- and [Fe4Pb18]4-, which contain rhombic Fe4 cores. The Fe-Fe bond lengths are all below 2.5 Å, distinctly shorter than in the corresponding Cu clusters, indicating the presence of Fe-Fe bonding. Subtle differences in the structure of the Fe4 core between the two clusters suggest that the change in tetrel element causes a change in electronic ground state, with a very short Fe-Fe bond length of 2.328 Å present across the diagonal of the rhombus in the lead case.
The endohedral Zintl-ion cluster [Fe3Sn18]4- contains a linear Fe3 core with short Fe-Fe bond lengths of 2.4300(9) Å. The ground state is a septet, with significant σ and π contributions to the Fe-Fe bonds. The Sn18 cage is made up of two partially fused Sn9 fragments, and is structurally intermediate between [Ni2CdSn18]6-, where the fragments are clearly separated and [Pd2Sn18]4-, where they are completely fused. It therefore represents an intermediate stage in cluster growth. Analysis of the electronic structure suggests that the presence of the linear Fe-Fe-Fe unit is an important factor in directing reactions towards fusion of the two Sn9 units rather than the alternative of oligomerization via exo bond formation.
We report here the structure of an endohedral plumbaspherene, [Cu4Pb22]4-, the gold analogue of which was previously postulated to be a "missing link" in the growth of larger clusters containing three and four icosahedral subunits. The cluster contains two [Cu2Pb11]2- subunits linked through a Cu2Pb4 trigonal antiprism. Density functional theory reveals that the striking ability of mixed Pb/coinage metal Zintl clusters to oligomerize and, in the case of Au, to act as a site of nucleation for additional metal atoms, is a direct consequence of their nd10(n + 1)s0 configuration, which generates both a low-lying (n + 1)s-based LUMO and also a high-lying Pb-centered HOMO. Cluster growth and nucleation is then driven by this amphoteric character, allowing the clusters to form donor-acceptor interactions between adjacent icosahedral units or to additional metal atoms.
The [Nb@As8]3- anion was first isolated from solution in 1986, and a number of isostructural [M@Pn8]n- clusters (M = Nb, Cr, or Mo; Pn = As or Sb; n = 2 or 3) have since been reported. We show here how anions of this class can be used as synthetic precursors that, in combination with sources of low-valent late transition metals (Cu and Ag), generate ternary polyarsenide cluster anions with unprecedented structural motifs. Chain type [MM'As16]4- (M = Nb or Ta; M' = Cu or Ag) units are found in compounds 2-5. These clusters contain a nortricyclane-like As7 cage and a [M@As8] crown, linked by a single As atom, and represent a fusion of two quite distinct branches of polyarsenide chemistry. Our analysis of the electronic structure confirms that the cluster retains many of the features of the component units. Electrospray ionization mass spectrometry reveals a series of smaller component ions containing 8-12 As atoms, the density functional theory-computed structures of which can be understood in terms of the pseudoelement concept. This work not only presents a new type of coordination mode for As clusters but also offers a point of entry for the rational design of multinary arsenic-based materials.
Density functional theory (DFT) calculations were employed to study the stabilities, electronic structures, and vibrational and bonding properties of dianionic pentacarbonyls [TM(CO)5]2- (TM = Cr, Mo, W). A D3h symmetry structure with singlet state was found to be the ground state and C-O stretching vibrational frequencies range from 1719 to 1766 cm-1, which are in excellent agreement with the experimental observations. The calculation results on bond dissociation energy for the CO loss revealed their stabilities. By employing energy decomposition analysis (EDA), the bonding nature between TM2- and (CO)5 was disclosed, in which the [TM(d)]2-â(CO)5π backdonations contribute largely to the orbital interactions while σ donation from the lone pair of CO to metal contributes moderately. Compared with those in the isoelectronic neutral hexacarbonyls TM(CO)6, the π backdonations are obviously larger in [TM(CO)5]2- because there are two extra electrons in (n- 1)d AOs of the center transition metal.
Gold nanoparticles have been used for centuries, both for decoration and in medical applications. More recently, many of the major advances in cluster chemistry have involved well-defined clusters containing tens or hundreds of atoms, either with or without a ligand shell. In this paper we report the synthesis of two gold/lead clusters, [Au8Pb33]6- and [Au12Pb44]8-, both of which contain nido [Au@Pb11]3- icosahedra surrounding a core of Au atoms. Analogues of these large clusters are not found in the corresponding Ag chemistry: instead, the Ag-centered nido icosahedron, [Ag@Pb11]3-, is the only isolated product. The structural chemistry, along with the mass spectrometry which shows the existence of [Au2Pb11]2- but not [Ag2Pb11]2-, leads us to propose that the former species is the key intermediate in the growth of the larger clusters. Density functional theory indicates that secondary π-type interactions between the [Au@Pb11]3- ligands and the gold core play a significant part in stabilizing the larger clusters.
We report the synthesis of two new cluster anions, [Cu4@E18]4- (E = Sn, Pb), in which a Cu4 subunit is incorporated into a continuous E18 tetrel cage. Both anions are characterized by X-ray crystallography and mass spectrometry, complemented by quantum-chemical calculations that highlight the relationships to known Zintl clusters, including the stannaspherenes and plumbaspherenes [M@Sn12]q- and [M@Pb12]q-, the Matryoshka bronze [Sn@Cu12@Sn20]12-, and also [Pd2@E'18]4- (E' = Ge, Sn).
The chemical bonding of Zintl clusters is still an evolving and hot topic in modern chemistry. In this paper we synthesized a novel [K([2.2.2]crypt)]4 [In8 Bi13 ] complex in a condensed phase. The quantum chemical calculations and X-ray data revealed that the compound consists of the 1:1 mixture of [Bi@In8 Bi12 ]3- and [Bi@In8 Bi12 ]5- clusters. To the date, those clusters are the largest binary clusters composed of In and Bi elements. Herein, we introduce a spherical aromatic description of chemical bonding for such clusters. We show through AdNDP, ELF, and induced magnetic field and quantitative NICS analyzes that both clusters are spherically aromatic which explains their high symmetry, stability, and peculiar magnetic properties. We believe that this work will help researchers in the further development and understanding of chemical bonding in Zintl clusters.
