Showing papers on "Carborane published in 2004"
TL;DR: In this article, an improved methodology was reported for the regioselective nitration of the phenyl groups of meso-tetraphenylporphyrin 1, using NaNO2 and TFA.
175 citations
TL;DR: In this paper, a review describes recent advances in the synthesis and structural characterization of organometallic complexes with 1, 2-dichalcogenolato-1,2-dicarba- closo -dodecaborane ligands, with emphasis on the complexes that show interesting reactivity patterns.
154 citations
TL;DR: Based on NMR and IR spectroscopy, H(CHB Cl ) can lay claim to be the strongest isolable acid presently known.
Abstract: Measure for measure: Several measures indicate that carborane acids of the type H(CHB11R5X6) (see scheme, green R, red X, gray H, pink B) for R = H, Cl and X = Cl, Br, I are the strongest pure Bronsted acids. Based on NMR and IR spectroscopy, H(CHB11Cl11) can lay claim to be the strongest isolable acid presently known.
143 citations
TL;DR: The molecular structures of derivatives of phenyl-ortho-carborane show remarkable and systematic variations with the degree of exo pi-bonding, which varies as expected with the pi-donor characteristics of the substituent.
Abstract: The structures of derivatives of phenyl-ortho-carborane bearing on the second cage hypercarbon atom a π-donor substituent (F, OH, O−, NH2, NH− and CH2−) were investigated by NMR, X-ray crystallography and computational studies. The molecular structures of these compounds, notably their cage C1–C2 distances and the orientations of their π-donor substituents (OH, NH2, NH− and CH2−) show remarkable and systematic variations with the degree of exo
π-bonding, which varies as expected with the π-donor characteristics of the substituent.
101 citations
TL;DR: The X-ray crystal structures of tert-butyl, tert-pentyl, and methyl-cyclopentyl cations have been determined with CHB 11Me5X6- counterions with the aim of isolating stable salts at room temperature when partnered with inert carborane anions.
Abstract: Author(s): Kato, Tsuyoshi; Reed, Christopher A | Abstract: Usually viewed as intermediates that become long-lived at low temperatures in superacidic media, simple alkyl carbocations such as the tert-butyl cation can be isolated as stable salts at room temperature when partnered with inert carborane anions. The X-ray crystal structures of tert-butyl (depicted), tert-pentyl, and methyl-cyclopentyl cations have been determined with CHB 11Me5X6- counterions (X= Br or Cl). C blue; H white; B yellow; X green.
94 citations
TL;DR: Decaborane olefin-hydroboration and alkyne-insertion reactions have been found to proceed in ionic liquid solvents without the need of a catalyst, providing important new, high-yield synthetic pathways to functionalized decaborane and o-carborane clusters.
Abstract: In contrast to reactions that have been observed in traditional organic solvents, decaborane olefin-hydroboration and alkyne-insertion reactions have been found to proceed in ionic liquid solvents without the need of a catalyst. These reactions now provide important new, high-yield synthetic pathways to functionalized decaborane and o-carborane clusters.
63 citations
TL;DR: Crystalline materials have been isolated and characterized from mixing the silver carborane salts with nitrile ligands, either terminal acetonitrile or potentially bridging alkanedinitriles, and all show coordination chain structures.
Abstract: Crystalline materials have been isolated and characterized from mixing the silver carborane salts Ag(CB11H12) or Ag[Co(C2B9H11)2] with nitrile ligands, either terminal acetonitrile or potentially bridging alkanedinitriles. Most of the complexes showed B−H···Ag interactions between the silver center and carborane anion. [Ag(acetonitrile)2(CB11H12)] has a hexagonal network structure. [Ag(malonitrile)2(CB11H12)] is a discrete dimeric complex, while [Ag4(succinonitrile)5(CB11H12)4], [Ag(glutaronitrile)2][Co(C2B9H12)2], and {Ag(glutaronitrile)[Co(C2B9H11)2]} all show coordination chain structures. The carborane anions in {Ag(adiponitrile)[Co(C2B9H11)2]} bridge between Ag centers to give a 3D CdSO4-related coordination polymer. The structure of [Ag(malonitrile)2](BF4) was also determined to have an unusual chiral diamondoid structure with a skewed 2-fold interpenetration.
63 citations
TL;DR: In this paper, the picolyl-functionalized o-carborane ligand CabNH (1; CabNH = 1-(2‘-picolyl)-o-Carborane) was prepared from the monolithium carborane LiHC2B10H10 (=LiCab) and 2-CH2ClC5H5N.
57 citations
TL;DR: DFT calculations on 2 (at the B3LYP/DZVP level) show small energy differences between the possible coordination isomers of this compound, with the favored geometry being one in which the [(Ph(3)P)Ag](+) fragment interacts with three of the [BCH(3)] vertices on the lower surface of the cage, similar to the experimentally observed structure of 4.
Abstract: The synthesis of the silver(I) salt of the highly methylated carborane anion [closo-1-H-CB11Me11]- is described, Ag[closo-1-H-CB11Me11] 1, which in the solid state shows close intermolecular Ag···H3C contacts. Addition of various monodentate phosphines to 1 results in the formation of the complexes (R3P)Ag[closo-1-H-CB11Me11] [R = Ph, 2; cyclohexyl (C6H11), 3; (3,5-Me2-C6H3), 4]. All these complexes show close intermolecular Ag···H3C contacts in the solid state that are considerably shorter than the sum of the van der Waals radius of methyl (2.00 A) and the ionic radius of silver(I) (1.29 A). For 2 and 3 there are other close intermolecular Ag···H3C contacts in the solid state, arising from proximate carborane anions in the crystal lattice. Addition of methyl groups to the periphery of the phosphine ligand (complex 4) switches off the majority of these interactions, leaving essentially a single cage interacting with the cationic silver−phosphine fragment through three CH3 groups. In solution (CD2Cl2) Ag··...
54 citations
TL;DR: The crystal structure of the isopropyl reagent, i-Pr(CHB(11)Me(5)Br(6)), has been determined, revealing covalence in the alkyl-carborane bonding, which contrasts with the free i- Pr(+) carbocation observed when the anion is less coordinating.
Abstract: A new class of potent electrophilic "R(+)" alkylating agents has been developed using weakly nucleophilic carborane anions as leaving groups. These reagents, R(CHB(11)Me(5)X(6)) (R = Me, Et, and i-Pr; X = Cl, Br), are prepared via metathesis reactions with conventional alkylating agents such as alkyl triflates, using the high oxophilicity of silylium ion-like species, Et(3)Si(carborane), as the driving force to obtain increased alkyl electrophilicity. The crystal structure of the isopropyl reagent, i-Pr(CHB(11)Me(5)Br(6)), has been determined, revealing covalence in the alkyl-carborane bonding. This contrasts with the free i-Pr(+) carbocation observed when the anion is less coordinating (e.g. Sb(2)F(11)(-)) or with tertiary alkyl centers, as in [tert-butyl][carborane] salts. In solution, the reagents exist as equilibrating isomers with the alkyl group at the 7-11 or 12 halide positions of the CB(11) icosahedral carborane anion. These alkylating agents are so electrophilic that they (a) react with alkanes at or below room temperature via hydride extraction to produce carbenium ions, (b) alkylate benzene without a Friedel-Crafts catalyst to give arenium ions, and (c) alkylate electron-deficient phosphorus compounds that are otherwise inert to conventional alkylating agents such as methyl triflate.
51 citations
TL;DR: The data suggest that Co-Co electronic communication is extensive (Class III) within individual sandwich units while intersandwich delocalization is weak or absent.
Abstract: Electronic interactions and metal-metal communication in a wide range of cobaltacarborane-hydrocarbon complexes containing one to six metal centers, and exhibiting a variety of modes of inter-cage connectivity and molecular architectures, have been investigated via cyclic voltammetry, controlled potential coulometry, and UV-visible spectroelectrochemistry. The properties of mixed-valent Co(III)/Co(IV) and Co(II)/Co(III) species that are generated on oxidation or reduction of dinuclear and polynuclear Co(III) complexes were examined and classified as Robin-Day Class I (localized), Class II (partially delocalized), or Class III (fully delocalized) systems. The extent of metal-metal communication between metallacarborane cage units is strongly influenced by the type of intercage connection (e.g., cage B-B or Cp-Cp); the vertexes involved (equatorial vs apical); the nature of the linking unit, if any; and the presence of substituents on the carborane cages. In multi-tripledecker complexes where three CpCo(C(2)B(3)H(4))CoCp units are linked through a central triethynyl benzene connector, the data suggest that Co-Co electronic communication is extensive (Class III) within individual sandwich units while intersandwich delocalization is weak or absent. An extended Huckel study of CpCoC(2)B(4)H(6) double-decker and CpCo(C(2)B(3)H(5))CoCp triple-decker sandwich model complexes shows significant differences in the orbital contributions involved in the HOMO and LUMO of the former vs the latter type. The calculations afford additional insight into the electronic structures and properties of these systems as elucidated by the experimental studies.
TL;DR: The nido-carborane lipid, which has a double-tailed moiety, was synthesized from heptadecanol in 5 steps and incorporated into distearoylphosphatidylcholine liposomes at a very high concentration.
TL;DR: The reportedly unprotonatable pentacyano-cyclo-pentadienide ion, C(5)(CN)(5)(-), can be protonated and silylated at the cyano N atom using electrophilic reagents derived from weakly coordinating carborane anions.
TL;DR: Bowl-shaped C-methylcalix[4]resorcinarene forms a 1:1 ball-and-socket nanostructure with o-carborane through two endo-cavity BC-H...pi hydrogen bonds, completely shrouding two carboranes.
Abstract: Bowl-shaped C-methylcalix[4]resorcinarene forms a 1:1 ball-and-socket nanostructure with o-carborane through two endo-cavity BCH⋅⋅⋅π hydrogen bonds. In the presence of 4′,2:6,4′′-terpyridine, two of these nanostructures are held together by four terpyridines through sixteen OH⋅⋅⋅N hydrogen bonds, completely shrouding two carboranes.
TL;DR: In this paper, the Pd-catalyzed cross-coupling reactions of B-I bond in m- and p-carboranes and cobalt bis(1,2-dicarbollide) anion with organomagnesium and organozinc compounds were studied.
TL;DR: Biodistributions of nido-1-succinylamido-[(131)I]carborane and closo- 1-suCCinylamidane were similar in mice, but blood clearance of the nido - compound was slower and the most rapid iodination and radioiodination reactions occurred with unsubstituted carboranes.
TL;DR: The 16-electron half-sandwich cobalt complex CpttCo[Se2C2(B10H10)] (Cptt = 5-1,3-tBu2C5H3) (3) has been synthesized by the reaction of [(THF)3LiSe 2C2B 10H10Li(THF)]2 (2) with CptTCo(CO)I2 (1) as mentioned in this paper.
TL;DR: Reaction of the lithium salt of 1-(2'-pyridyl)-ortho-carborane, Li[1-R-1,2-C(2)B(10)H(10)] with sulfur, followed by hydrolysis, gave the mercapto-o- carborane which forms chiral crystals containing helical chains of molecules linked by intermolecular S-H...N hydrogen bonds.
Abstract: Reaction of the lithium salt of 1-(2′-pyridyl)-ortho-carborane, Li[1-R-1,2-C2B10H10]
(R = 2′-NC5H4), with sulfur, followed by hydrolysis, gave the mercapto-o-carborane, 1-R-2-SH-1,2-C2B10H10 which forms chiral crystals containing helical chains of molecules linked by intermolecular S–H⋯N hydrogen bonds. The cage C(1)–C(2) and exo C(2)–S bond lengths (1.730(3) and 1.775(2)
A, respectively) are indicative of exo SC π bonding. The tin derivative 1-R-2-SnMe3-1,2-C2B10H10, prepared from Li[1-R-1,2-C2B10H10] and Me3SnCl, crystallises with no significant intermolecular interactions. The pyridyl group lies in the C(1)–C(2)–Sn plane, oriented to minimise the N⋯Sn distance (2.861(3)
A). The tin environment is distorted trigonal bipyramidal with axial N and Me. The gold derivative 1-R-2-AuPPh3-1,2-C2B10H10, prepared from Li[1-R-1,2-C2B10H10] and AuCl(PPh3), reveals no N⋯Au interaction in its crystal structure.
TL;DR: Icosahedral metal-monocarbollide complexes with carbon atoms carried by exo-polyhedral -NR3 or -NR2 groups have an extensive chemistry, as illustrated by complexes of ruthenium, osmium, rhodium, molybdenum, tungsten and rhenium as discussed by the authors.
TL;DR: In this article, the carborane anion is bound to the metal center, and this process can be frozen out at −50 °C. This cycle can be repeated a number of times without apparent decomposition, with the anion acting in a "catch and release" manner, stabilizing the metal centre when needed.
TL;DR: The formation of intramolecular CH...X(N,O) bonds and their persistence in solution were studied by X-ray crystallography and NMR techniques and provided new insight in the theory of CH)...X bonds, which appear stronger and less rare than it was previously thought.
Abstract: The formation of intramolecular CH...X(N,O) bonds and their persistence in solution were studied by X-ray crystallography and NMR techniques in two different rotamers of a molecule containing the ortho-carborane cage, an amide group and a quinoline ring. Experimental data were confirmed by theoretical ab initio calculations. From the resolved structure of the two forms of this potentially active drug for boron neutron capture therapy, accurate bonding and geometric parameters were extracted for this non-classic hydrogen interaction, and their strength was calculated. These findings provided new insight in the theory of CH...X bonds, which appear stronger and less rare than it was previously thought.
TL;DR: In this article, a family of η5-CpFe(CO)2-substituted closo-carboranes was synthesized and characterized, including cyclic voltammetry measurements.
TL;DR: In this paper, it was suggested that the origin of the photoluminescence of o -carborane is a phosphorescence, which is not a genuine property of the material.
TL;DR: The ethyleneoxide modified 3CTAs were good substrate of thymidine kinase 1 (TK1) and poor substrates of human mitochondrial thymazine kinase 2 (Tk2) as determined in phosphoryl transfer assays.
TL;DR: Several series of structurally related three-ring esters containing benzene, cyclohexane, bicyclo[2.2] octane and p-carborane rings were synthesized and their mesogenic properties investigated using thermal analysis and optical microscopy as mentioned in this paper.
Abstract: Several series of structurally related three-ring esters containing benzene, cyclohexane, bicyclo[2.2.2]octane and p-carborane rings were synthesized and their mesogenic properties investigated using thermal analysis and optical microscopy. Carborane derivatives show only nematic phases, while the richest smectic polymorphism (up to three phases) was observed in the biphenyl series D. The structure–property relationships were studied by comparison of T NI between series. The ring effectiveness in stabilization of nematic phases generally follows the order carborane
TL;DR: In this article, the thermal stability of poly(m -carborane-siloxane) elastomers was investigated using differential scanning calorimetry (DSC) and infra-red analysis.
TL;DR: A series of sixteen three-ring esters of carboxylic acids derived from p-carborane, bicyclo[2.2] octane and benzene were synthesized and their mesogenic properties investigated using polarizing microscopy and DSC.
Abstract: A series of sixteen three-ring esters of carboxylic acids derived from p-carborane, bicyclo[2.2.2]octane and benzene were synthesized and their mesogenic properties investigated using polarizing microscopy and DSC. The stability of the nematic phases follows the order BCO > Ph > 12-vertex > 10-vertex (or C > D > A > B). The biphenol derivatives 1 and 2 show significantly more rich smectic behavior than the pyrimidinylphenol esters 3 and 4. Most of the esters show the expected effect on FLC properties of a host mixture. The exceptions are BCO derivatives 2C and 4C, which significantly lower the normalized Ps, and the carborane derivative 4A which significantly increased the normalized Ps and γs values. In contrast to the hydrocarbon analogs, carborane esters lower the tilt angle.
TL;DR: The ESR line shape analysis proved that no dramatic changes were induced in the liposome environment by carborane insertion, and QELS data showed that the overallliposome structure was preserved, with a slight decrease in the mean hydrodynamic radius and increase in polydispersity caused by the guest molecules.
TL;DR: An increment system forming a set of quantitative rules that govern the relative stabilities of 11-vertex nido-boranes and carboranes is presented, which are thermodynamically more stable than known positional isomers and show a behavior independent of the cluster size.
Abstract: An increment system forming a set of quantitative rules that govern the relative stabilities of 11-vertex nido-boranes and carboranes is presented. Density functional theory computations at the B3LYP/6-311+G//B3LYP/6-31G level with ZPE corrections were carried out for 61 different boron hydride and carborane structures from [B(11)H(14)](-) to C(4)B(7)H(11) to determine their relative stabilities. Disfavored structural features that destabilize a cluster structure relative to a hypothetical ideal situation were identified and weighted by so-called energy penalties. The latter show additive behavior and allow us to reproduce (within 5 kcal mol(-)(1)) the DFT computed relative energies. Energy penalties for four structural features, i.e., adjacent carbon atoms, CC, a hydrogen atom bridging between a carbon and a boron atom, CH-B, an endo-terminal hydrogen atom at an open face carbon atom, CH(2) and an endo-H between two carbon atoms, C(BH(2))C for the 11-vertex nido-cluster are quite similar to those reported for the 6-vertex nido-cluster, thus showing a behavior independent of the cluster size. Hydrogen structural features, however, vary strongly with the cluster size. Two unknown 11-vertex nido-carboranes were identified which are thermodynamically more stable than known positional isomers.
TL;DR: The Cp ring in [RuCl(Cp)(PPh3)2] undergoes an apparent nucleophilic attack by the carbanion carb- to give an H-/carb- exchange process, which is favoured by coordination of the hydride to the ruthenium centre.
Abstract: The Cp ring in [RuCl(Cp)(PPh3)2] undergoes an apparent nucleophilic attack by the carbanion carb−
(Hcarb = 2-Me-1,2-dicarba-closo-dodecaborane), to give an H−/carb− exchange process, which is favoured by coordination of the hydride to the ruthenium centre.