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1. Al(OR ^F ) ₃ (R ^F = C(CF ₃ ) ₃ ) activated silica: a well-defined weakly coordinating surface anion

   https://doi.org/10.1039/C9SC05904K  

   Culver, Damien B.; Venkatesh, Amrit; Huynh, Winn; Rossini, Aaron J.; Conley, Matthew P. (February 2020, Chemical Science)

   Weakly Coordinating Anions (WCAs) containing electron deficient delocalized anionic fragments that are reasonably inert allow for the isolation of strong electrophiles. Perfluorinated borates, perfluorinated aluminum alkoxides, and halogenated carborane anions are a few families of WCAs that are commonly used in synthesis. Application of similar design strategies to oxide surfaces is challenging. This paper describes the reaction of Al(OR F ) 3 *PhF (R F = C(CF 3 ) 3 ) with silica partially dehydroxylated at 700 °C (SiO 2-700 ) to form the bridging silanol Si–OH⋯Al(OR F ) 3 ( 1 ). DFT calculations using small clusters to model 1 show that the gas phase acidity (GPA) of the bridging silanol is 43.2 kcal mol −1 lower than the GPA of H 2 SO 4 , but higher than the strongest carborane acids, suggesting that deprotonated 1 would be a WCA. Reactions of 1 with NOct 3 show that 1 forms weaker ion-pairs than classical WCAs, but stronger ion-pairs than carborane or borate anions. Though 1 forms stronger ion-pairs than these state-of-the-art WCAs, 1 reacts with alkylsilanes to form silylium type surface species. To the best of our knowledge, this is the first example of a silylium supported on derivatized silica. 

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2. Probing copper-boron interactions in the Cu ₂ B ₈ ⁻ bimetallic cluster

   https://doi.org/10.1116/6.0001833  

   Kulichenko, Maksim; Chen, Wei-Jia; Choi, Hyun Wook; Yuan, Dao-Fu; Boldyrev, Alexander I.; Wang, Lai-Sheng (July 2022, Journal of Vacuum Science & Technology A)

   Borophenes are atom-thin boron layers that can be grown on coinage metal substrates and have become an important class of synthetic 2D nanomaterials. The interactions between boron and substrates are critical to understand the growth mechanisms of borophenes. Here, we report an investigation of copper-boron interactions in the Cu 2 B 8 − bimetallic cluster using photoelectron spectroscopy and quantum chemical calculations. Well-resolved photoelectron spectra are obtained at several photon energies and are combined with theoretical calculations to elucidate the structures and bonding of Cu 2 B 8 − . Global minimum searches reveal that Cu 2 B 8 − consists of a Cu 2 dimer atop a B 8 molecular wheel with a long Cu–Cu bond length close to that in Cu 2 + . Chemical bonding analyses indicate that there is clear charge transfer from Cu 2 to B 8 , and the Cu 2 B 8 − cluster can be viewed as a [Cu 2 + ]-borozene complex, [Cu 2 + ][B 8 2– ]. In the neutral cluster, no Cu–Cu bond exists and Cu 2 B 8 consists of two Cu + centers interacting with doubly aromatic B 8 2− borozene. The charge transfer interactions between Cu and boron in the Cu 2 B 8 − cluster are analogous to charge transfer from the copper substrate to the first borophene layer recently reported to be critical in the growth of bilayer borophenes on a Cu(111) substrate. 

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3. The metallo-formate anions, M(CO ₂ ) ⁻ , M = Ni, Pd, Pt, formed by electron-induced CO ₂ activation

   https://doi.org/10.1039/c9cp01915d  

   Liu, Gaoxiang; Ciborowski, Sandra M.; Zhu, Zhaoguo; Chen, Yinlin; Zhang, Xinxing; Bowen, Kit H. (May 2019, Physical Chemistry Chemical Physics)

   The metallo-formate anions, M(CO 2 ) − , M = Ni, Pd, and Pt, were formed by electron-induced CO 2 activation. They were generated by laser vaporization and characterized by a combination of mass spectrometry, anion photoelectron spectroscopy, and theoretical calculations. While neutral transition metal atoms are normally unable to activate CO 2 , the addition of an excess electron to these systems led to the formation of chemisorbed anionic complexes. These are covalently bound, formate-like anions, in which their CO 2 moieties are significantly reduced. In addition, we also found evidence for an unexpectedly attractive interaction between neutral Pd atoms and CO 2 . 

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4. B ₃₁ ⁻ and B ₃₂ ⁻ : chiral quasi-planar boron clusters

   https://doi.org/10.1039/C9NR01524H  

   Chen, Qiang; Chen, Teng-Teng; Li, Hai-Ru; Zhao, Xiao-Yun; Chen, Wei-Jia; Zhai, Hua-Jin; Li, Si-Dian; Wang, Lai-Sheng (May 2019, Nanoscale)

   Chirality plays an important role in nature. Nanoclusters can also exhibit chiral properties. We report herein a joint experimental and theoretical investigation on the geometric and electronic structures of B 31 − and B 32 − clusters, using photoelectron spectroscopy in combination with first-principles calculations. Two degenerate quasi-planar chiral C 1 enantiomers ( I and II , 1 A) with a central hexagonal vacancy are identified as the global minima of B 31 − . For B 32 − , two degenerate boat-like quasi-planar chiral C 2 structures ( VI and VII , 2 A) with a central hexagonal vacancy are also found as the global minima, with a low-lying chair-like C i B 32 − ( VIII , 2 A u ) also present in the experiment as a minor isomer. The chiral conversions in quasi-planar B 31 − and B 32 − clusters are investigated and relatively low barriers are found due to the high flexibility of these monolayer clusters, which feature multiple delocalized σ and π bonds over buckled molecular surfaces. 

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5. High-Resolution Photoelectron Imaging of IrB ₃ ⁻ : Observation of a π-Aromatic B ₃ ⁺ Ring Coordinated to a Transition Metal

   https://doi.org/10.1002/anie.201902406  

   Czekner, Joseph; Cheung, Ling Fung; Kocheril, G. Stephen; Kulichenko, Maksim; Boldyrev, Alexander I.; Wang, Lai-Sheng (July 2019, Angewandte Chemie International Edition)

   We report a high-resolution photoelectron imaging and theoretical study of the IrB3‾ cluster. Two isomers are observed experimentally with electron affinities (EAs) of 1.3147(8) eV and 1.937(4) eV. Quantum calculations reveal two nearly degenerate isomers competing for the global minimum, both with a B3 ring coordinated with the Ir atom. One of the isomers consists of a B3 ring with a bridge-bonded Ir (Cs, 2A), which has the higher EA; and the second isomer features a tetrahedral structure (C3v, 2A1), which has the lower EA. The neutral tetrahedral structure is predicted to be overwhelmingly more stable than all other isomers. Chemical bonding analyses show that the neutral C3v isomer involves significant covalent Ir–B bonding and weak ionic bonding with charge transfers from B3 to Ir, which can be viewed as an Ir‾(η3-B3+) complex. The current study reports the first example of a boron-to-metal charge transfer complex and provides evidence of a π-aromatic B3+ ring coordinated to a transition metal. 

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