Nickelacarborane-Supported Bis-N-heterocyclic Carbenes

Advances in the selective functionalization of B(3,6)-H of o-carboranes

This review summarizes the methodologies for the selective functionalization of the B(3,6) vertices of o-carboranes, including the deboration-capitation reaction, the coupling reaction of B-X (X = I, Br) bonds, reactions of 1,3-dehydro-o-carborane and [3-N2-o-C2B10H11][BF4] as well as transition-metal-catalyzed B-H activation. These works offer a versatile toolbox for synthesizing B(3,6)-substituted o-carborane derivatives and will promote their applications in material science, pharmaceutical chemistry, and related disciplines.

Palladium-Catalyzed Cross-Coupling Reactions of Carboranes with Alkenes via Selective B-H Bond Activation

A palladium-catalyzed Heck-type cross-coupling reaction of carboranes with alkenes in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) was realized. This reaction shows good B(9) selectivity for m-carboranes and is also suitable for o- and p-carborane. Meanwhile, a series of mono-, di-, and trisubstituted alkenes were compatible substrates to afford the alkenylated products in 16-89% yields. The 1,2-bis(carboranyl)ethylene was first synthesized by the reaction of vinyltrimethylsilane and m-carborane. Further transformations of the C═C bond in the product were examined by hydroboration oxidation, oxidation, hydroboration, and bromination reaction to generate corresponding B(9)-functionalized m-carboranes.

3D N-heterocyclic covalent organic frameworks for urea photosynthesis from NH3 and CO2

Artificial photosynthesis of urea from NH3 and CO2 seems to remain still essentially unexplored. Herein, three isomorphic three-dimensional covalent organic frameworks with twofold interpenetrated ffc topology are functionalized by benzene, pyrazine, and tetrazine active moieties, respectively. A series of experiment results disclose the gradually enhanced conductivity, light-harvesting capacity, photogenerated carrier separation efficiency, and co-adsorption capacity towards NH3 and CO2 in the order of benzene-, pyrazine-, and tetrazine-containing framework. This in turn endows tetrazine-containing framework with superior photocatalytic activity towards urea production from NH3 and CO2 with the yield of 523 μmol g-1 h-1, 40 and 4 times higher than that for benzene- and pyrazine-containing framework, respectively, indicating the heterocyclic N microenvironment-dependent catalytic performance for these three photocatalysts. This is further confirmed by in-situ spectroscopic characterization and density functional theory calculations. This work lays a way towards sustainable photosynthesis of urea.

A 12-Vertex Metallacarborane of Silver(I)

The discovery of ferrocene in 1951 was a significant landmark in the field of organometallic chemistry, and since then, numerous sandwich- or half-sandwich metallic complexes have been reported. However, silver stands as an intriguing exception in this regard, and knowledge of its bonding situation has remained undisclosed. Herein, unprecedented 12-vertex metallacarboranes of Ag(I) (2a and 2b) were synthesized through the reaction of sodium hexamethyldisilazide (NaHMDS) with the mixture of nido-C2B9 carborane anion-supported N-heterocyclic carbene precursors (1a and 1b) and [Ag(PPh3)Cl]4. The X-ray structural analysis of the resulting metallacarboranes revealed a unique "slipped" half-sandwich structure, which is a rarity among cyclopentadienyl analogues. DFT calculations provided insights into the asymmetric π-interactions between the pentagonal C2B3 face and the silver ion.

9,9'-Bis-o-carboranes: synthesis and exploration of properties

A highly efficient Pd-catalyzed B(9)-H/B(9)-H oxidative dehydrogenation coupling of carboranes to synthesize 9,9'-bis-o-carboranes has been developed. The properties and derivatization of 9,9'-bis-o-carborane were also examined, which provided diverse bis-o-carborane derivatives and bis-nido-carborane.

Nickel(II) and Palladium(II) Complexes with η5:κ1(N)-Coordinated Dicarbollide Ligands Containing Pendant Pyridine Group

A series of C- and B-substituted nido-carborane derivatives with a pendant pyridyl group was prepared. The synthesized compounds were used as ligands in the complexation reactions with bis(triphenylphosphine)nickel(II) and palladium(II) chlorides to give six new metallacomplexes with unusual η5:κ1(N)-coordination of the metal center. The single crystal structures of 1-(NC5H4-2'-S)-1,2-C2B10H11, 1-(NC5H4-2'-CH2S)-1,2-C2B10H11, Cs [7-(NC5H4-2'-CH2S)-7,8-C2B9H11] closo- and nido-carboranes and 3-Ph3P-3-(4(7)-NC5H4-2'-S)-closo-3,1,2-NiC2B9H10 and 3-Ph3P-3-(4(7)-NC5H4-2'-CH2S)-closo-3,1,2-NiC2B9H10 metallacarboranes were determined using single crystal X-ray diffraction.