OsB9−: An Aromatic Osmium-Centered Monocyclic Boron Ring

Abstract

Transition-metal-centered monocyclic boron wheels are important candidates in the family of planar hypercoordinate species that show intriguing structure, stability and bonding situation. Through the detailed potential energy surface explorations of MB9− (M = Fe, Ru, Os) clusters, we introduce herein OsB9− to be a new member in the transition-metal-centered borometallic molecular wheel gallery. Previously, FeB9− and RuB9− clusters were detected by photoelectron spectroscopy and the structures were reported to have singlet D9h symmetry. Our present results show that the global minimum for FeB9− has a molecular wheel-like structure in triplet spin state with Cs symmetry, whereas its heavier homologues are singlet molecular wheels with D9h symmetry. Chemical bonding analyses show that RuB9− and OsB9− display a similar type of electronic structure, where the dual σ + π aromaticity, originated from three delocalized σ bonds and three delocalized π bonds, accounts for highly stable borometallic molecular wheels.

Two‐layer molecular rotors: A zinc dimer rotating over planar hypercoordinate motifs

“…To facilitate their experimental confirmation, the simulated infrared spectrums of MB 8 Zn 2 (M = Be, Ru, Os) and photoelectron spectrums of MB 7 Zn 2 − (M = Be, Ru, Os) clusters were displayed at left and right of Figure 6 at the BP86/def2‐TZVP level, respectively. Note that the BP86 functional presents a good performance on couples of metal‐doped boron clusters studied by both theoretical calculations and photoelectron spectrums 27,60–64 . The high‐symmetry C 2 v BeB 8 Zn 2 exhibits major IR active peaks at 571 and 599 cm −1 (Figure 6A), and major IR active peaks of RuB 8 Zn 2 and OsB 8 Zn 2 are similar, being 145, 365 cm −1 (Figure 6B) and 144, 357 cm −1 (Figure 6C), respectively.…”

“…Thus, 60 two-layer configurations were initially formed and further optimized at the PBE0/def2-TZVP level. As a result, two-layer forms for the most of planar nona-and deca-coordinate metals [27][28][29]42,43 and Hgbased species cannot be maintained (see Figure S1), and they are not further considered in this work. Additionally, two-layer forms in some cases are not the lowest-energy structures by simply checking their random isomers (see Figures S2-S4).…”

“…Up to date, a series of middle‐size pure boron clusters (B 11 −/0/+ , B 13 −/0/+ , B 15 −/0/+ , B 20 −/2− ) 15–17,19–22 and large‐size B 40 23 and B 39 − 24 borospherenes have been explored as barrier‐free rotation of internal planar moieties or interconversion between six‐ and seven‐membered rings, respectively. These attractive dynamical phenomena can be attributed to the extraordinary ability of boron to form multicenter bonding, owing to its electron‐deficient nature, which also results in many intriguing properties of boron clusters, such as unusual geometries and bonding, 11,25,26 double aromaticity, 27–29 and unique 2D‐to‐3D structural transition 30–32 …”

“…) [15][16][17][19][20][21][22] and large-size B 40 23 and B 39 À24 borospherenes have been explored as barrier-free rotation of internal planar moieties or interconversion between six-and seven-membered rings, respectively. These attractive dynamical phenomena can be attributed to the extraordinary ability of boron to form multicenter bonding, owing to its electrondeficient nature, which also results in many intriguing properties of boron clusters, such as unusual geometries and bonding, 11,25,26 double aromaticity, [27][28][29] and unique 2D-to-3D structural transition. [30][31][32] Doped boron clusters by metals have strongly enriched the family of molecular rotors, and novel dynamical behaviors were also explored.…”

“…A few successful examples mentioned above show that boron wheels stabilized by delocalized σ and π bonds is a key factor in the boron-based multi-layer rotors. Numerous studies reveal that planar hypercoordinate metals consisting of monocyclic boron rings and metals also possess highly delocalized σ and π bonds, [27][28][29][42][43][44][45] whether thus they can be regarded as one promising layer to form multi-layer rotors? In this work, 60 isolated clusters composed of X 2 dimer (X = Zn, Cd, Hg) and previously reported planar hypercoordinate metals were considered as shown in Table S1.…”