Xiaolei Zhang

Bio: Xiaolei Zhang is an academic researcher from Nanjing University. The author has contributed to research in topics: Carborane & Carbene. The author has an hindex of 10, co-authored 16 publications receiving 454 citations. Previous affiliations of Xiaolei Zhang include Nanyang Technological University & Jiangnan University.

Selective Catalytic B–H Arylation of o-Carboranyl Aldehydes by a Transient Directing Strategy

Abstract: Carboranyl aldehydes are among the most useful synthons in derivatization of carboranes. However, compared to the utilization of carboranyl carboxylic acids in selective B–H bond functionalizations, the synthetic application of carboranyl aldehydes is limited due to the weakly coordinating nature of the aldehyde group. Herein, the direct arylation of o-carboranyl aldehydes has been developed via Pd-catalyzed cage B–H bond functionalization. With the help of glycine to generate a directing group (DG) in situ, a series of cage B(4,5)-diarylated- and B(4)-monoarylated-o-carboranyl aldehydes were obtained in good to excellent yields with high selectivity. A wide range of functional groups are tolerated. The aldehyde group in the B–H arylated products could be readily removed or transformed into o-carboranyl methanol. A plausible catalytic cycle for B–H arylation was proposed based on control experiments and stoichiometric reactions, including the isolation of a key bicyclic palladium complex.

B–H···π Interaction: A New Type of Nonclassical Hydrogen Bonding

Abstract: For the first time, nonclassical hydrogen (H)-bonding involving a B–H···π interaction is described utilizing both quantum chemical predictions and experimental realization. In the gas phase, a B–H···π H-bond is observed in either B2H6···benzene (ΔE = −5.07 kcal/mol) or carborane···benzene (ΔE = −3.94 kcal/mol) complex at reduced temperatures. Ir-dimercapto-carborane complexes [Cp*Ir(S2C2B10H10)] are designed to react with phosphines PR3 (R = C6H4X, X = H, F, OMe) to give [Cp*Ir(PR3)S2C2B10H10] for an investigation of B–H···π interactions at ambient temperatures. X-ray diffraction studies reveal that the interaction between the carborane BH bonds and the phosphine aryl substituents involves a BH···π H-bond (H···π distance: 2.40–2.76 A). 1H NMR experiments reveal that B–H···π interactions exist in solution according to measured 1H{11B} signals at ambient temperatures in the range 0.0 ≤ δ ≤ 0.3 ppm. These are high-field shifted by more than 1.5 ppm relative to the 1H{11B} signals obtained for the PMe3 analog...

Pd(II)-catalyzed synthesis of bifunctionalized carboranes via cage B–H activation of 1-CH2NH2-o-carboranes

Abstract: Aminoalkyl carboranes are anticipated to be valuable synthons toward the synthesis of bifunctionalized carboranes. However, direct cage boron derivation of these carborane derivatives has not been solved. Herein, the reversible conversion of catalytically infeasible o-carboranyl methylamines (1-CH2NH2-o-carboranes) into bidentate imines initiates Pd-mediated cage B-H activation. As a result, an amine coordinated bicyclic Pd(ii) complex (3) has been isolated and proven to be the catalytically active intermediate for highly site-selective B-H diarylation of o-carboranyl methylamines. Using glyoxylic acid as an inexpensive and commercially available transient directing reagent, a wide range of cage B(4,5)-diarylated free primary o-carboranyl methylamines were prepared in good to excellent yields with the avoidance of the pre-installation and removal of a directing group. This method provides easy access to cage boron functionalized o-carboranyl methylamines with potential for application in pharmaceuticals.

Supramolecular Luminescent Sensors

Abstract: There is great need for stand-alone luminescence-based chemosensors that exemplify selectivity, sensitivity, and applicability and that overcome the challenges that arise from complex, real-world media. Discussed herein are recent developments toward these goals in the field of supramolecular luminescent chemosensors, including macrocycles, polymers, and nanomaterials. Specific focus is placed on the development of new macrocycle hosts since 2010, coupled with considerations of the underlying principles of supramolecular chemistry as well as analytes of interest and common luminophores. State-of-the-art developments in the fields of polymer and nanomaterial sensors are also examined, and some remaining unsolved challenges in the area of chemosensors are discussed.

Methods to produce B–C, B–P, B–N and B–S bonds in boron clusters

Abstract: Boranes, heteroboranes and metallacarboranes, all named as boron clusters, offer an alternative to typical organic molecules or organic molecular materials Carbon and boron share the important property of self-catenation thus these elements can produce individually large and sophisticated molecules Boron clusters and organic molecules display electronic, physical, chemical and geometrical characteristics manifestly different These differences highlight the complementarity of organic molecules and boron clusters, and therefore the feasibility or necessity to produce hybrid molecules incorporating both types of fragments To join these two types of fragments, or alternatively these two types of molecular compounds, tools are needed In this review the current methods of producing boron clusters with carbon, B–C, nitrogen, B–N, phosphorus, B–P and sulphur bonds, B–S, are indicated As there are many existing borane clusters of different sizes, heteroboranes and metallacarboranes, the revision of methods to generate the B–C, B–P, B–S, and B–N bonds has been restricted to the most widely used boron clusters; [B12H12]2−, dianionic and an example of a borane, 1,2-C2B10H12, neutral and an example of a heteroborane, and [Co(C2B9H11)2]−, monoanionic and an example of a metallacarborane

Highly Emissive Organic Single-Molecule White Emitters by Engineering o-Carborane-Based Luminophores.

Abstract: The development of organic single-molecule solid-state white emitters holds a great promise for advanced lighting and display applications. Highly emissive single-molecule white emitters were achieved by the design and synthesis of a series of o-carborane-based luminophores. These luminophores are able to induce multiple emissions to directly emit high-purity white light in solid state. By tuning both molecular and aggregate structures, a significantly improved white-light efficiency has been realized (absolute quantum yield 67 %), which is the highest value among the known organic single-molecule white emitters in the solid state. The fine-tuning of the packing modes from H- to J- and cross-stacking aggregates as well as intermolecular hydrogen bonds are successful in one molecular skeleton. These are crucial for highly emissive white-light emission in the solid state.

Synthesis, Structures of Benzoxazolyl Iridium(III) Complexes, and Applications on C–C and C–N Bond Formation Reactions under Solvent-Free Conditions: Catalytic Activity Enhanced by Noncoordinating Anion without Silver Effect

Abstract: Several new bisbenzoxazolyl iridium(III) complexes have been synthesized and characterized through X-ray crystallography. These complexes exhibit excellent catalytic activity in C–C and C–N bond formation reactions from the alkylation of amine with amine, amine with alcohol, ketone with alcohol, and alcohol with alcohol through a borrowing hydrogen reaction. Moreover, these iridium(III) complexes are effective catalysts for the alkylation of amine with alcohol and ketone with alcohol under solvent-free conditions. The catalytic activity of these complexes is greatly enhanced by noncoordinating, while the experiments have excluded the possibility of a “silver effect” (bimetallic catalysis or silver-assisted metal catalysis) from the experiments.