Ronglin Zhong’s research while affiliated with Jilin University and other places

Complexes containing odd‐electron Be−Be bonds are still rare until now. Hereby, a series of neutral di‐beryllium amidinate complexes containing a Be−Be bond were explored theoretically. The complexes with direct chelation with the Be2 dimer by the bidentate amidinate (AMD) ligands are always corresponding to their global minimum structures. The detailed bonding analyses reveal that the localized electrons of the Be−Be fragment can be adjusted by the amount of AMD ligands because each AMD ligand only takes one electron from the Be2 fragment. Meanwhile, the hybridization of the central Be atom also changes as the number of AMD ligands increases. In particular, the sp³‐hybridized single‐electron Be−Be bond is firstly identified in the tri‐AMD‐ligands‐chelated neutral D3h‐Be2(AMD)3 complex, which also possesses the higher stability compared to its monoanionic D3h‐Be2(AMD)3⁻ and monocationic C3‐Be2(AMD)3⁺ analogues. Importantly, our study provides a new approach to obtain a neutral odd‐electron Be−Be bond, namely by the use of radical ligands through side‐on chelation.

C–N cross-coupling reaction has been achieved by photoredox-mediated iridium/nickel dual catalysis, but its mechanism is still controversial in these reactions. Theoretical mechanistic study of a highly chemoselective C–N cross-coupling of pyrrolidine with 4-bromobenzotrifluoride has been performed by density functional theory (DFT) calculations. The oxidation state modulation mechanisms initiated by reductive quenching and oxidative quenching are unfavourable due to the mismatched redox potentials and slow electron transfer rates. In contrast, a novel radical mechanism merging reductive quenching (IrIII–*IrIII–IrII–IrIII) and nickel catalytic cycles (NiII–NiIII–NiII–NiII) is favourable. It consists of four major processes: exogenous base triggered single electron transfer (SET) and hydrogen atom transfer (HAT) to generate nitrogen-centred radical, radical capture by nickel(II) dibromide, SET to regenerate iridium(III), and the rate-determining σ-bond metathesis to achieve the C–N cross-coupling. Furthermore, the suppression effect caused by α-substitution of pyrrolidine on the reaction is dominantly attributed to the steric effect rather than the electronic effect. Unlike the C–N cross-coupling, the concerted σ-bond metathesis involving nickel(II) is inapplicable for the C–O and C–S cross-couplings due to the high energy barriers. This study is expected to provide new mechanistic insights for metallaphotoredox-catalysed C–N cross-coupling.

Zn=Zn double bonded‐especially double‐π bonded‐systems are scarce due to strong Coulomb repulsion caused by the Zn atom's internally crowded d electrons and very high energy of the virtual π orbitals in Zn2 fragments. It is also rare for Zn atoms to exhibit negative oxidation states within reported Zn−Zn bonded complexes. Herein, we report Zn=Zn double‐π bonded octahedral clusters Zn2M4 (M=Li, Na) bridged by four alkali metal ligands, in which the central Zn atom is in a negative oxidation state. Especially in D4h−Zn2Na4, the natural population analysis shows that the charge of the Zn atom reaches up to −0.89 |e| (−1.11 |e| for AIM charge). Although this cooperation inevitably increases the repulsion between two Zn atoms, the introduction of the s¹‐type ligands results in occupation of degenerated π orbitals and the electrons being delocalized over the whole octahedral framework as well, in turn stabilizing the octahedral molecular structure. This study demonstrates that maintaining the degeneracy of the π orbitals and introducing electrons from equatorial plane are effective means to construct double‐π bonds between transitional metals.

Palladium-catalyzed C−F bond arylation of pentafluorobenzene was theoretically investigated as an example of aryl−F bond functionalization. DFT computations show that C3-regioselective arylation of pentafluorobenzene occurs more favorably than C1 and C2-ones as reported experimentally, through oxidative addition of C−F bond to Pd0 species, transmetalation and reductive elimination of C−C bond. Oxidative addition of C−F bond is the rate-determining and regioselectivity-determining step. The lower energy transition state of oxidative addition of C3−F bond (TS-C3) arises from a larger stabilization energy between Pd0(BrettPhos) and distorted pentafluorobenzene moieties in TS-C3 than those in TS-C1 and TS-C2. The larger stabilization energy is a result of lower σ* orbital energy of distorted C3−F bond than C1−F and C2−F ones, which leads to a larger charge transfer from Pd dπ orbital to the σ* orbital of C3−F bond. Results suggest that both σ* orbital energy and bond dissociation energy are important factors for determining the reactivity of C−F bond. Also, the activation barriers of C−F bond with different substitution groups follow the order: NO2 < COOMe < CN ~ CF3 < F, which is approximatively consistent with the order of electron-withdrawing ability of those groups. It is theoretically predicted here that NMe2-substituted BrettPhos is better for C−F bond cleavage than BrettPhos, where three NMe2 groups are introduced to BrettPhos instead of the isopropyl groups.

External electric field (EEF), as a metal-free catalyst, catalyzing the Markovnikov hydrosilylation of styrene was studied for the first time. Compared to the field-free situation, the barrier height was almost halved upon application of an EEF with a field strength of 180 ×10-4 au in the direction perpendicular to the “bond axis”. Therefore, the use of EEF not only resolved the questions of separation of homogeneous catalysts from the reaction mixture, but also facilitated the reaction by decreasing its barriers. Furthermore, we found that the lower the energy of transition state (TSX) and the higher the energy of HOMO of reactant (R1’), the lower the barrier height of the hydrosilylation. Hopefully, this study could provide a guide for the experiment of external electric field.

Herein, we present a series of Be2X4Y2 clusters (X = Li, Na and Y = Li, Na, K) containing Be≡Be triple bond, which are constructed by six alkali metals as electron-donating ligands. By virtue of the electrostatic potential mapping of the precedent Be=Be double-π bonded D4h-Be2X4 clusters, the Be2X4Y2 trans-bent geometries and the Be≡Be triple bond inside are both well interpreted. More remarkably, we firstly identify a perfect classical Be≡Be triple bond in D4h-Be2Na4K2 and its Wiberg bond index of Be-Be (WBIBe-Be) reaches up to 2.43. Meanwhile, our strategy provides a new approach to explain the trans-bent structure caused by terminal coordination.

Stable phenalenyl (PLY) radical π‐dimers still play an important role for new multifunctional materials owing to intriguing molecular structure and unusual pancake π‐π bonding. Herein, we design a new biphenalenyl biradicaloid (1) that consisting of two PLYs and one benzene ring linkage tethered by single bond, presenting open‐shell character. Further, three π‐dimers (a1, b1 and c1) combined with 1 and conventional biphenalenyl biradicaloid (a, b and c) that are capable of forming two staggered PLY dimers, exhibiting short interlayer distance between the monomers. Interestingly, the analysis of the frontier molecular orbital reveal that two bonding orbitals, namely, their the highest occupied molecular orbitals (HOMO and HOMO‐1) are doubly occupied. The results reveal that three π‐dimers display two parallel pancake bonds. Moreover, small diradical and tetraradical characters, large interaction energy and strong aromaticity indicate the stability of these π‐dimers. The present work creates a new class of strong pancake bonding and might be utilized in devising an array of materials.

Carbon-boron-nitride heteronanotubes (BNCNT) have attracted a lot of attention because of their adjustable properties and potential applications in many fields. In this work, a series of CA, PA and HA armchair BNCNT models were designed to explore their nonlinear optical (NLO) properties and provide physical insight into the structure-property relationships; CA, PA and HA represent the models that are obtained by doping the carbon segment into pristine boron nitride nanotube (BNNT) fragments circularly around the tube axis, parallel to the tube axis and helically to the tube axis, respectively. Results show that the first hyperpolarizability (β0) of an armchair BNCNT model is dramatically dependent on the connecting patterns of carbon with the boron nitride fragment. Significantly, the β0 value of PA-6 is 2.00 × 10(4) au, which is almost two orders of magnitude larger than those (6.07 × 10(2) and 1.55 × 10(2) au) of HA-6 and CA-6. In addition, the β0 values of PA and CA models increase with the increase in carbon proportion, whereas those of HA models show a different tendency. Further investigations on transition properties show that the curved charge transfer from N-connecting carbon atoms to B-connecting carbon atoms of PA models is essentially the origin of the big difference among these models. This new knowledge about armchair BNCNTs may provide important information for the design and preparation of advanced NLO nano-materials.