On the Aromaticity of Square Planar Ga₄^2- and In₄^2- in Gaseous NaGa₄^- and NaIn₄^- Clusters

Abstract

We investigated the electronic structure and chemical bonding of two bimetallic clusters NaGa4- and NaIn4-. Photoelectron spectra of the anions were obtained and compared with ab initio calculations. We found that the ground state of the two anions contains a square planar dianion interacting with a Na+ cation. The Ga4(2-) and In4(2-) dianions both possess two delocalized pi electrons and are considered to be aromatic, similar to that recently found in Al4(2-). Using calculations for a model compound, we showed that a recently synthesized Ga4-organometallic compound also contains an aromatic -Ga4(2-)- unit, analogous to the gaseous clusters.

Growth Mechanism and Chemical Bonding in Scandium‐Doped Copper Clusters: Experimental and Theoretical Study in Concert

“…[47,48] rings, respectively. [49] The nucleus independent chemical shift (NICS) [50] is À22.1 ppm in the center of the copper ring, and has a similar value of À22.3 ppm in the center of the cage, which supports the aromatic character of this clus- ter. The analysis of the dissected NICS computed for the canonical molecular orbitals (CMO-NICS) shows that the 1s orbital (which has 78 % contribution from the s atomic orbitals) has a large diatropic contribution to the total NICS.…”

Sandwich Complexes Based on the “All‐Metal” Al42− Aromatic Ring

“…Antiaromaticity, in contrast, is associated with either incomplete occupation of the delocalized p/s bonding orbitals or to partial occupation of the delocalized p/s antibonding orbitals. Al 4 2À constitutes a rare example of multiple-fold aromaticity, [1,9] possessing one p-aromatic system with two electrons and two s-aromatic systems with two electrons each. Note that all the three systems fulfil the Hückel (4n+2) electron counting rule with n = 0.…”

“…This concept helps the understanding of simultaneous contributions to aromaticity within the same molecular structure as arising from various delocalized bonding systems, and should be of general applicability irrespective of whether the molecule is organic or inorganic. [8] Following the characterization of the Al 4 2À molecule, analogous structures formed by Ga 4 2À , In 4 2À [9] and XAl 3 2À (X = Si, Sn, Ge and Pb) [10] have also been synthesized. The metal rings of these compounds present properties similar to Al 4 2À , namely, high magnetic shielding, [11] large ring current, [12] similarly derived antiaromatic structures [13] and large resonance energies.…”

Structural Dependence of Magnetic Shielding Properties in Al<SUB>4</SUB>Li<SUB>4</SUB> Clusters

“…The concept of aromaticity used to explain the additional stability of organic conjugated ring molecules was expanded to inorganic systems by the discovery of aromaticity in organometallic, [1][2][3] all-metal clusters, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and recently transition-metal-containing clusters with aromaticity. [21][22][23] Interest in this field has been increased by the finding of an antiaromatic all-metal cluster.…”