Carboranes. III. Reactions of the Carboranes

Grafstein, Daniel; Bobinski, Jack; Dvorak, Joseph; Smith, Harry; Schwartz, Nelson N.; Cohen, Murray S.; Fein, Marvin M.

doi:10.1021/ic50010a009

Cited by 127 publications

(32 citation statements)

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“…The ten boron and two carbon atoms of closo-carboranes form a highly hydrophobic icosahedral cage which is stable under strongly acidic and oxidizing conditions. However, in the presence of bases such as alkoxides [7], amines [8], and fl uoride ion [9], the most electropositive boron atom is regioselectively removed with formation of the negatively charged nido-carborane cage [10]. Nido-carboranes are soluble in a variety of solvents, depending on the nature of their counterion; they are soluble in organic solvents in the form of quaternary ammonium salts and water-soluble in the form of sodium or potassium salts.…”

Section: Introductionmentioning

confidence: 99%

Syntheses and properties of carboranylpyrroles

Clark

Fabre

Fronczek

et al. 2005

J. Porphyrins Phthalocyanines

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Synthetic routes to mono-and di-carboranylpyrroles (1-5) bearing the carborane groups linked either directly to the 3-and/or 4-positions of the pyrrole ring or via one or two methylene spacers are described. Several X-ray structures of key intermediates are presented and discussed. Carboranylpyrroles can be cyclotetramerized to afford carboranylporphyrins in low to moderate yields, depending on the number of carborane cages and their linkage to the pyrrole ring. The best yields of porphyrin were obtained with pyrrole 3, bearing a two carbon spacer between the carborane and pyrrole units. The electrochemical polymerization of pyrroles 2 and 3 gave functionalized conducting polymer fi lms with increased overoxidation resistance and thermal stability compared with unsubstituted polypyrrole. Dicarboranylpyrrole 4 did not electropolymerize under a variety of experimental conditions, whereas pyrrole 5 formed only soluble oligomers.

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Section: Introductionmentioning

confidence: 99%

Syntheses and properties of carboranylpyrroles

Clark

Fabre

Fronczek

et al. 2005

J. Porphyrins Phthalocyanines

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“…Incubation of an ether solution (1) with an equal amount 25% aq. HCI overnight results in cleavage of the dimethyl esters to give the tetracarboranyl porphyrin diacid (2) in quantitative yield with no evidence of carboranyl ester cleavage. Esters of carborane carboxylic acid are known to be extremely resistant to acid-catalyzed cleavage despite the strongly electropositive nature of…”

Section: Methodsmentioning

confidence: 98%

Synthesis and Properties of Tetrakis-Carborane-Carboxylate Esters of 2,4-BIS-(α,β-Dihydroxyethyl) Deuteroporphyrin IX

Kahl

Koo

1992

Progress in Neutron Capture Therapy for Cancer

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“…At present, it is not known whether the bridging hydrogen effectively blocks the apical position or if preferential metal-carborane attractions favor the exo-polyhedral positions of the cesium ions. Other metalating agents, including Grignard reagents, have also been used to remove the terminal C-H bonds [17]. Other metalating agents, including Grignard reagents, have also been used to remove the terminal C-H bonds [17].…”

Section: Group 1 Metallaboranes and Metallacarboranesmentioning

confidence: 99%

METALLABORANES AND METALLACARBORANES OF s-BLOCK ELEMENTS

Rana¹,

Maguire²,

Hosmane³

et al. 2000

Main Group Metal Chemistry

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The syntheses, structures and reactivity of the compounds formed by the incorporation of a group 1 or group 2 element into a borane or carborane cage have been reviewed. The group 1 boranes were generally found to comprise compounds in which lithium ions replace bridged hydrogens in a borane cage. Some of these lithiated compounds were found to crystallize from solution as oligomers. The carboranes showed much more variations in which a number of group 1 metals occupied both bridging, apical or cowwo-positions of the «/'Jo-carborane anions. The group 2 boranes were restricted to those of beryllium and magnesium. Examples of compounds were described where the beryllium ions occupy both bridging and apical positions, while only bridging magnesiums were reported. As with the group 1 compounds, the group 2 carboranes were more numerous, with examples of beryllium, magnesium, calcium and strontium metals being incorporated into the electron deficient cages. This review will cover the published work on the compounds in which an s-block (group 1 or 2) metal is incorporated into the polyhedral borane or carborane cage; it will not cover those compounds where the metal is a member of an exopolyhedral, spectator group. A quick review of the some of the nomenclature and electronic structure conventions used in these cage compounds will be helpful in our discussions. To start, consider two of the simplest hydrides of carbon and boron, ethane (C,H 6 ) and diborane (B 2 H 6 ). Although they have similar formulas, their internal bonding and chemical properties are quite different. Both molecules possess six hydrogen atoms that can each furnish one orbital and one electron for bonding and two second period main group elements, each contributing one s and three ρ valence orbitals, giving a total of 14 orbitals to be used in bonding. Tne two molecules differ in the number of electrons that are delocalized in bonding; ethane has 14, one for every orbital, while diborane has only 12. Therefore, ethane can be classified as an "electron precise" compound and its formula can be rationalized in terms of a series of twocenter-two-electron (2c-2e) bonds holding the molecule together. On the other hand, in B 2 H 6 , the number of electrons (12) is less than the number of orbitals (14), such compounds are said to be "electron deficient , and one must resort to multi-centered bonds in order to rationalize their formulas. For example, diborane can be described as being held together by two 3c-2e B-H-B bridge bonds and four 2c-2e B-Η terminal bonds. Multicentered bonds, bridged hydrogens, as well as 2o2e terminal B-Η bonds are all characteristics of the borane cages. Many of the compounds in the following sections will be pictured using line formulas and ORTEP diagrams. In electron precise compounds, such as ethane, it is understood that each line connecting adjacent nuclei represents a 2c-2e electron pair bond. However, in an electron deficient compound, this is not always the case. In interpreting these formulas it is convenient to separate ...

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Carboranes. III. Reactions of the Carboranes

Cited by 127 publications

References 0 publications

Syntheses and properties of carboranylpyrroles

Syntheses and properties of carboranylpyrroles

Synthesis and Properties of Tetrakis-Carborane-Carboxylate Esters of 2,4-BIS-(α,β-Dihydroxyethyl) Deuteroporphyrin IX

METALLABORANES AND METALLACARBORANES OF s-BLOCK ELEMENTS

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