Facile and mild deboronation of o-carboranes using cesium fluoride

Site-specific synthesis of a hybrid boron-graphene salt

We report the first example of an ionic graphene salt containing boron. An anionic charge is introduced to the graphene surface by means of 7,8-nido-[C2B9H11](-) carborane clusters covalently and electronically bound to the graphene lattice, and this new material was isolated as its Cs(+) salt.

Synthesis of the fluorohydridoborate anions [BHF3]− and [1-HF2B-9,12-X2-closo-1,2-C2B10H9]− (X = H, I): deboronation of 1,2- and 1,7-dicarba-closo-dodecaboranes with anhydrous [Me4N]F

The [BHF₃]⁻ anion represents the first example of an anion of the series [BH_nF_4−n]⁻ (n = 1–3), which is obtained via deboronation of closo-1,2-C₂B₁₀H₁₂ or closo-1,7-C₂B₁₀H₁₂ with anhydrous [Me₄N]F.

Nucleoside bearing boron clusters and their phosphoramidites – building blocks for modified oligonucleotide synthesis

Synthesis of four canonical nucleoside-closo-/nido-carborane conjugates, their phosphoramidites, their electrochemical characteristics and the first example of the X-ray structure of a nucleoside-boron cluster conjugate.

Syntheses and reductions of C-dimesitylboryl-1,2-dicarba-closo-dodecaboranes

An investigation ofC-dimesitylboryl-ortho-carboranes, 1-(BMes₂)-2-R-1,2-C₂B₁₀H₁₀(1and2), reveals that the carborane is the electron-acceptor and the mesityl group is the electron-donor in these dyads.

Unprecedented formation of polycyclic diazadiborepine derivatives through cage deboronation of m-carborane

An unprecedented deboronation reaction of icosahedral carboranes is described, in which a BH group of m-carborane is detached from the cage and incorporated into an unusual nido-carborane-anellated diazadiborepine ring system.

Synthesis of closo- and nido-biscarboranes with rigid unsaturated linkers as precursors to linear metallacarborane-based molecular rods

Several biscarborane-type derivatives of 8-iodo-1,2-dicarba-closo-dodecaborane (1), suitable as the precursors of linear metallacarborane-based molecular rods, were prepared. The synthesized closo-compounds contained two carborane moieties connected through a rigid linear unsaturated linker. The linkers were based on ethynylene and para-phenylene fragments and their combinations. The deboronation of all reported closo-compounds was selective and afforded nido-products with open pentagonal faces on opposite sides of the molecule, parallel to each other and perpendicular to the main molecular axis. All of the closo and nido products were characterized by a variety of physical methods (NMR, HRMS, IR). The structures of closo-carboranes 3, 6, 9, and 14 and nido-carboranes 15 and 17 were established by X-ray diffraction.

A new approach to the synthesis of functional derivatives of nido-carborane: alkylation of [9-MeS-nido-7,8-C2B9H11]⁻

A series of asymmetrically substituted sulfonium derivatives of nido-carborane [9-R(Me)S-nido-7,8-C2B9H11] (R = Et, Pr, Bu, Bn, CH=CH2, CH2CH=CH2, CH2C≡CH, CH=C=CH2) were prepared by alkylation of the 9-methylthio-nido-7,8-carborane. The synthesized compounds are the first examples of diastereomers combining nido-carborane and sulfonium chiral centers.

Alpha (α-) and beta (β-carboranyl-C-deoxyribosides: syntheses, structures and biological evaluation

The syntheses of the unprotected neutral closo-carboranyl-C-deoxyriboses, starting from anomeric mixture of 1-ethynyldeoxyriboses, and their corresponding open-cage nido-derivatives have been described. The structures of both the α- and β-anomers were confirmed by single-crystal X-ray diffraction. While limited water solubility of the neutral closo-anomers led to high cytotoxicity, their cesium salts (nido-species) exhibited higher water solubility leading to lower cytotoxicity. However, in vitro boron neutron capture therapy (BNCT) investigation using the murine squamous cell carcinoma (SCCVII) cell lines showed that there are no significant differences between the survival fractions of the two species.

The first indoleamine-2,3-dioxygenase-1 (IDO1) inhibitors containing carborane

The first examples of indoleamine-2,3-dioxygenase-1 (IDO1) inhibitors containing a carborane cage are reported.

Carboranylporphyrazines for anti-cancer therapies: synthesis and physicochemical properties

The synthesis, the salient physicochemical properties, and liposome insertion of carboranyl-alkylthio-porphyrazines, a new family of potential BNCT agents, are here reviewed together with recent progresses in their metalation and conversion in the water-soluble counterparts.

Carborane-containing poly(fluorene): response to solvent vapors and amines

Hybrid conjugated polymers containing carborane directly bonded in the aromatic backbone repeat structure have interesting electronic bonding structures and are potentially useful new materials in organic electronics. Conjugated polymers based on o-carborane are particularly interesting for applications in sensing and detection because of the cage's unique bonding scheme and its bent geometry. Poly(fluorene) containing o-carborane displays multiple emission pathways that can be modulated through interactions with small molecules. In this paper, we report that films of poly(fluorene) with o-carborane in the backbone function as vapochromatic photoluminescent sensors toward volatile organic molecules.

Synthesis, structural characterization, and reactivity of Group 4 metallacarboranes bearing the ligand [H2C(C5Me4)(C2B9H10)]3-

A new organic-inorganic hybrid ligand H(2)C(C(5)Me(4)H)(C(2)B(10)H(11)) (2) has been prepared. A selective deboration reaction with piperidine in ethanol resulted in the isolation of [Me(3)NH][H(2)C(C(5)Me(4)H)(C(2)B(9)H(11))] (3). An amine-elimination reaction of 3 with [Zr(NMe(2))(4)] produced a neutral metal-amide complex [η(5):η(5)-H(2)C(C(5)Me(4))(C(2)B(9)H(10))]Zr(NMe(2))(NHMe(2)) (4). The double-ring-opening reaction of 4 with tetrahydrofuran (THF) afforded [η(5):η(5)-H(2)C(C(5)Me(4))(C(2)B(9)H(10))]Zr (OCH(2)CH(2)CH(2)CH(2))(2)N(CH(3))(2) (5). Treatment of the trianionic salt of 3 with [MCl(4)(thf)(2)] gave complexes [{η(5):η(5)-H(2)C(C(5)Me(4))(C(2)B(9)H(10))}M(μ-Cl)(2)][Li(thf)(2)] (M=Zr (6), Hf (7)). Reaction of 6 with LiCH(2)TMS generated the ionic species [{η(5):η(5)-H(2)C(C(5)Me(4))(C(2)B(9)H(10))}Zr(CH(2)TMS)(2)][Li(thf)(3)] (9). Interaction of complex 6 with KCH(2)(NMe(2))-o-C(6)H(4) led to the formation of the neutral metal alkyl complex [η(5):η(5)-H(2)C(C(5)Me(4))(C(2)B(9)H(10))]Zr[σ:σ-CH(2)(NMe(2))-o-C(6)H(4)] (10). All complexes have been fully characterized by various spectroscopic techniques and elemental analyses. Some were further confirmed by single-crystal X-ray analyses.

Synthesis and properties of carborane-appended C(3)-symmetrical extended pi systems

A series of C(3)-symmetric pi-conjugated compounds containing three to six o-carborane clusters have been synthesized by employing palladium-catalyzed Suzuki coupling reactions and palladium-catalyzed acetylation reactions, followed by silicon tetrachloride mediated trimerization reactions. Carborane-containing extended trimers were found to emit blue light. Incorporation of o-carborane clusters into extended pi-conjugated systems led to 22-70% enhancement of their relative fluorescence quantum yields. Decapitation of o-carborane clusters made these extended trimers water soluble, and their aqueous solutions were also found to be fluorescent, but with a reduced fluorescence intensity. The carborane-appended pi-conjugated compounds are found to be extremely thermally stable, and for some of these compounds only 10% mass loss occurred at temperatures close to 500 degrees C. The DSC thermograms of smaller C(cage)-appended trimers indicate the occurrence of solid-solid phase transitions.

Boron-enriched star-shaped molecule via cycloaddition reaction

The facile synthesis of a thermally stable carborane appended symmetrical star-shaped molecule having six bulky o-carborane clusters on the periphery, thereby containing sixty boron atoms was accomplished via a cobalt-catalyzed [2+2+2] cycloaddition reaction.

Synthesis of a new class of carborane-containing star-shaped molecules via silicon tetrachloride promoted cyclotrimerization reactions

Symmetrical star-shaped molecules with carborane clusters on the periphery have been synthesized in good yields via silicon tetrachloride mediated cyclotrimerization reactions of 9-benzyl derivatives of carboranes with acetyl group substitution on the benzene ring. Facile functionalization of these symmetrical core structures with 1-iodoheptane and trivinylchlorosilane produce compounds which could be used as liquid crystalline substances and precursors for synthesis of higher order carbosilane dendrons.

Dicarba-closo-dodecaborane(12) derivatives of phosphonium salts: easy formation of nido-carborane phosphonium zwitterions

The first examples of arylphosphonium salts containing a dicarba-closo-dodecaborane(12) (closo-carborane) are reported; in contrast to the 1,12-carborane derivative, the 1,2- and 1,7-isomers undergo a facile deboronation reaction in polar solvents to afford the corresponding nido-carborane phosphonium zwitterions.

“Water-stable boron-iodinated dicarbollide dianions [7,8-nido-C2H2B9I9]2−and [7,8-nido-C2H2B9I8H]2−”

The reaction of 3,4,5,7,8,9,10,11,12-I(9)-1,2-closo-C(2)B(10)H(3) with KOH/EtOH gave a mixture of the boron periodinated [1,2,3,4,5,6,9,10,11-I(9)-7,8-nido-C(2)B(9)H(2)](2-) and the highly iodinated on boron [1,2,4,5,6,9,10,11-I(8)-7,8-nido-C(2)B(9)H(3)](2-) in approximately 50% each. Moreover, 3,4,5,6,7,8,9,10,11,12-I(10)-1,2-closo-C(2)B(10)H(2) was reacted with KOH/EtOH to purely produce [1,2,3,4,5,6,9,10,11-I(9)-7,8-nido-C(2)B(9)H(2)](2-). It is the first dinegative dicarbollide stable in water or protic solvent reported in literature.

Synthesis and Structural Characterization of Symmetrical closo-4,7-I2-1,2-C2B10H10 and [(CH3)3NH][nido-2,4-I2-7,8-C2B9H10]

The boron-atom insertion reaction of nido-9,11-I(2)-7,8-C(2)B(9)H(9)(2-), with the HBCl(2):SMe(2) complex yields closo-4,7-I(2)-1,2-C(2)B(10)H(10), 1, in excellent yield. Although the two boron atoms (B3 and B6) nearest to the carbon atoms in 1 are equally available for attack by nucleophiles, the boron-degradation reaction of 1 with alkoxide ion occurs only at the B6 vertex, yielding regioselectively [(CH(3))(3)NH][nido-2,4-I(2)-7,8-C(2)B(9)H(10)], 2. The molecular structures of 1 and 2 have been determined by X-ray diffraction studies. Crystallographic data are as follows. For 1, monoclinic, space group P2(1)/n, a = 6.9199(19) Angstroms, b = 23.9560(7) Angstroms, c = 7.2870(2) Angstroms, beta = 94.081(4) degrees, V = 1204.9(6) Angstroms(3), Z = 4, rho(calcd) = 2.18 g cm(-3), R = 0.020, R(w) = 0.0610; for 2, orthorhombic, space group Pca2(1), a = 14.1141(7) Angstroms, b = 7.0276(4) Angstroms, c = 16.4602(9) Angstroms, V = 1632.7(15) Angstroms(3), Z = 4, rho(calcd) = 1.81 gcm(-3), R = 0.022, R(w) = 0.0623.