A Rh^III-catalyzed C–H allylation of electron-deficient arenes, heteroarenes, and alkenes at room temperature was developed with allyl bromide. The reaction was carried out in diethyl ether without dehydration, and C–H activation was assisted by the directing anionic nitrogen of the aniline-derived amide. Following the allylation, a domino cycling synthesis of 3,4-dihydroisoquinolin-1(2H)-ones with N-bromosuccinimide (NBS) through intramolecular aminobromination of the introduced double bond was achieved.

Phosphorescent transition-metal complexes (PTMCs) have attracted great interest because of their excellent properties which may lead to promising applications in optoelectronics. In recent years, carboranes have been demonstrated to be a novel and effective tool to tune phosphorescence of PTMCs. This Concept article deals with the advances of carborane-functionalized PTMCs for potential optical applications. The discussions are focused on the design strategies and synthetic procedures leading to carborane-functionalized PTMCs, the influence of carboranes on the optical properties of PTMCs, and the promising optical applications of this interesting class of phosphorescent materials.

Nitro compounds are important intermediates in synthetic organic chemistry and the chemical industry. Herein, the efficient copper-catalyzed [10 % Cu(NO₃)₂·3H₂O] nitration of anilides was developed by using TBN (tert-butyl nitrite) as a nitrating reagent to give the corresponding nitro-substituted aromatic products in good to excellent yields. The use of TBN also led to the selective nitration of acrylamides at room temperature to afford only the (E) isomer of the nitration product. A series of anilides and acrylamides with a broad array of functional groups were well-tolerated by this procedure. This synthetic method has many advantages, which include inexpensive starting materials, mild reaction conditions, a fast reaction rate, and high yields. A mechanistic investigation indicates that a nitro radical, which is generated from the thermal homolysis of TBN, is involved in the two nitration processes.

2-Thienylpyridyl iridium(III) complexes containing an o-, m-, or p-carboranylvinyl-2,2′-bipyridine ligand and various counteranions (denoted o-PF₆, m-BF₄, m-PF₆, m-SbF₆, m-ClO₄, m-OTf, m-NO₃, m-BPh₄, m-F, m-Cl, and p-PF₆) were synthesized by using C-formyl carboranes as starting materials. The solid-state structures of o-PF₆, m-PF₆, m-ClO₄, and m-BF₄ showed that the cations form twisted cavities in which the anions are fixed by multiple hydrogen bonds. Anion–hydrogen interactions were investigated for nine m-carborane-based complexes with different counteranions. All carborane-based iridium(III) complexes show similar phosphorescence yields in solution but significantly different emission in the solid state. Anion-exchange titration and theoretical calculations revealed the relationships between structures and optical properties. The size of the anion and CH⋅⋅⋅X anion–hydrogen bonds strongly influence the phosphorescence quantum yield in the solid state. In particular, the C_carH⋅⋅⋅X hydrogen bonds between the carboranyl unit and the anion play an important role in solid-state phosphorescence. Complex p-PF₆ was successfully applied in phosphorescence-lifetime bioimaging owing to its low toxicity and near-infrared emission.

New iridium tetrazolate complexes containing o-, m-, or p-carboranyl substitution in different positions of a phenylpyridine ligand have been prepared. The carborane isomers and the effect of their substitution position in the tuning of optical properties have been examined. The neutral complexes with the carboranyl substituent on the phenyl ring in meta position relative to the metal exhibit redshifted emission bands in contrast to blueshifts for those with carboranyl in para position. All cationic complexes display evidently blueshifted dual-peak emission compared with the carborane-free complex (c-TZ) with a broad single-peak emission. Introduction of carborane leads to a blueshift over 70 nm relative to c-TZ. Carboranes also significantly improve phosphorescence efficiency (Φ_P) and lifetime (τ), that is, Φ_P=0.64 versus 0.21 (c-TZ) and τ=880 ns versus 241 ns (c-TZ). The unique hydrophilic nido-carborane-based Ir^III complex nido-o-1 shows the largest phosphorescence efficiency (abs Φ_P=0.57) among known water-soluble iridium complexes, long emission lifetime (τ=4.38 μs), as well as varying emission efficiency and lifetime with O₂ content in aqueous solution. Therefore, nido-o-1 has been used as an excellent oxygen-sensitive phosphor for intracellular O₂ sensing and hypoxia imaging.

The 16-electron half-sandwich complex CpCo(Se₂C₂B₁₀H₁₀) (1, Cp = cyclopentadienyl) reacts with FcC(O)C≡CH in CH₂Cl₂ at ambient temperature to give [{FcC(O)CCH}(Se₂C₂B₁₀H₁₀)] (3) and [CpCo(Se₂C₂B₁₀H₉){CH₂CC(O)Fc}] (4). Complex 3 is generated by the alkyne addition to the 1,2-dicarba-closo-dodecaborane-1,2-diselenolate ligand in 1 with the loss of the CpCo unit. In 4, metal-induced B–H activation occurs in the B(3)/B(6) position of carborane followed by the formation of a C–B bond. In MeOH the reaction leads to an unexpected product, [{FcC(O)CHCH}CpCo(Se₂C₂B₉H₉){CH₂CC(O)Fc}] (5), which contains two alkynes and a nido-C₂B₉ cage. In MeOH, 4 can further react with the alkyne to give 5. In the presence of silica, 4 loses the CpCo unit to afford [{FcC(O)CCH₂}(Se₂C₂B₁₀H₉)] (6), which is a symmetrical molecule with the B–CH₂ unit retained. All of these complexes have been characterized by IR, NMR, elemental analysis, mass spectrum, and single-crystal X-ray diffraction analysis.

Biointeractions between two organometallic compounds, a pair of ferrocene-substituted dithio-o-carborane isomers (C₁₄H₂₀B₁₀FeS₂; denoted as FcSB1 and FcSB2), and myoglobin (Mb) have been investigated by means of electrochemistry, fluorescence, circular dichroism, and UV/Vis absorption spectroscopy. Our observations demonstrate that FcSB1 and FcSB2 could coordinate to the axial position trans to the histidine imidazole that induces the change of the heme iron from the high spin state to the low spin state and the changes of the conformation of the aromatic fluorophores of the selected heme protein. Such influences attribute to the structural features of FcSB1 and FcSB2 containing sulfur donor atoms and hydrophobic ferrocenyl and carboranyl units that leads to specific binding modalities with Mb. This study provides an insight into the understanding of relevant biointeractions between the new type of ferrocene–carborane conjugates and hemoproteins, and might shed light on the promising bioapplications of these multifunctional organometallic complexes.

The reaction of the 16e half-sandwich complex [CpCo(S₂C₂B₁₀H₁₀)] (1 S; Cp: cyclopentadienyl) with ethynylferrocene in CH₂Cl₂ at ambient temperature leads to [CpCo(S₂C₂B₁₀H₉)(CH₂CFc)] (2 S; Fc: ferrocenyl) and 1,2,4-triferrocenylbenzene. In 2 S, B substitution occurs at the carborane cage in the position B(3)/B(6) with the formation of a CB bond. In the presence of the protic solvent MeOH, 2 S loses a CpCo fragment to generate [(CH₂CFc)(S₂C₂B₁₀H₉)] (3 S). On the other hand, 2 S can take a free CpCo fragment to form [(CpCo)₂(S₂C₂B₉H₈)(CHCFc)] (4 S) containing a nido-C₂B₉ unit. In sharp contrast, [CpCo(Se₂C₂B₁₀H₁₀)] (1 Se) does not react with the alkyne in CH₂Cl₂, but in MeOH [(CHCFc)(Se₂C₂B₁₀H₁₀)] (5 Se) is generated without the presence of a CpCo unit. The reaction of 1 with dimethyl acetylenedicarboxylate at ambient temperature leads to insertion compounds [CpCo(E₂C₂B₁₀H₁₀){(MeO₂C)CC(CO₂Me)}] (6 S, E=S; 6 Se, E=Se). Upon heating, 6 S rearranges to two geometrical isomers [CpCo(S₂C₂B₁₀H₉){(MeO₂C)CCH(CO₂Me)}] (7 S) and [CpCo(S₂C₂B₁₀H₉){(MeO₂C)CHC(CO₂Me)}] (8 S). In both, BH functionalization takes place at the carborane cage in the position B(3)/B(6), but 7 S is a 16e complex with an olefinic unit in a Z configuration, and 8 S is an 18e complex containing an alkyl BCH group. Further treatment of 7 S with dimethyl acetylenedicarboxylate at ambient temperature affords two B-disubstituted complexes at the carborane cage in the positions of the B(3) and B(6) sites, that is, [CpCo(S₂C₂B₁₀H₈){(MeO₂C)CCH(CO₂Me)}₂] (9 S) and [CpCo(S₂C₂B₁₀H₈){(MeO₂C)CHC(CO₂Me)}{(MeO₂C)CCH(CO₂Me)}] (10 S). Compound 9 S is a 16e complex with two olefinic units in E/E configurations, whereas 10 S is an 18e species containing both an olefinic substituent and an alkyl BCH unit. The reaction of 7 S with methyl acetylenemonocarboxylate at ambient temperature leads to the sole 16e compound [CpCo(S₂C₂B₁₀H₈){CHCH(CO₂Me)}{(MeO₂C)CCH(CO₂Me)}] (11 S). In contrast, 6 Se does not rearrange. All new complexes 2 S–4 S, 5 Se, 6 Se, and 7 S–11 S were characterized by NMR spectroscopy (¹H, ¹¹B, ¹³C) and X-ray structural analyses were performed for 2 S–4 S, 5 Se, 6 Se, and 7 S–9 S.