Methyl carboranes

A recent X-ray characterization of the cyclopentyl cation 33 generated with methyl carboranes has shown a perfect planar structure around the carbocation center [bond angles CH3-C+-CH2= 124.9 and 125.2°, CH2-C+-CH2= 109.9° bond distances CH3-C+ = 1.46 A, CH2-C+ = 1.45 A).123... 

A solution of methyl carborane (6.32 mmol) dissolved in 20 ml of diethyl ether was cooled to —78°C and then treated with 4.20 ml n-BuLi (6.72 mmol 1.6M in n-hexane) and stirred for 30 minutes. The mixture was warmed to ambient temperature, stirred for 4 hours, and treated with cyclohexene oxide (6.80 mmol) at 0°C. It was then stirred for 6 hours and quenched with 10 ml of water. The organic phase was separated, and the aqueous phase extracted twice with 25 ml of diethyl ether. The combined organics were dried using MgS04 and concentrated. The residue was re-crystallized in n-hexane, and the product was isolated in 86%yield, MP= 101-103°C... 

PETN TNT and for carboranes (and their mixts) the following were listed methyl-carboranes, n-propylcarborane, iso-propyl-carborane, vinylcarborane, isopropenylace-tylene, etc. Mixing of org polynitro compds, with carboranes produced very sensitive or spontaneously detonating expls. As an example was cited a homogeneous mixt prepd by adding slowly to 18.4 parts isopro-penylcarborane (agitated in a reactor by bubbling a stream of N), 78.4 parts of C(N02)4. C(N02)4 itself is not an expl,... 

Methyl abstraction of Cp2ZrMe2 with a trityl salt of a highly methylated carborane anion, [GPh [closo-HCBuMen], shown in Equation (47), leads to formation of the cationic complex 727 in which the methyl zirconocene cation is closely associated with the methylated carborane anion through the Zr(/x-CH3)B motif.562 The Zr- H3G interaction is maintained in solution, as shown by a change in chemical shift for the methyl group... 

Fig. 13. Water-cooled alembic column for distillation of (bromo-methyl)carborane. A) ground-glass joint for connection to high-vacuum system (B) loose-fitting glass-wool plug (C) water Jacket ...

The B-methylated carboranes, such as the permethylated para-carborane [(CH3),oC2B,oH2], and the octa-methylated meta-carborane [(CH3)8C2B,oH4] possess a number of unique properties. 

In contrast, lithiocarborane reacts with a variety of halides to give mono-substituted carboranes. Carboranecarboxylic acid is obtained by acid hydrolysis of methyl carborane-l-carboxylate (334), which in turn can be directly prepared from decaborane (Section III, C, 1). In comparison, dimethyl 1,2-carboranedicarboxylate cannot be hydrolyzed to the diacid with acidic reagents and in the presence of aqueous base, hydrolysis occurs only with difficulty and in poor yield, affording the salt of the diacid (XXXVIII) 327). Furthermore, the diester can neither be transesterified nor converted to the diamide via ammonolysis 334). In general, the diacid... 

The disilanickela complex 21 was also found to be a good catalyst for the dehydrogenative double silylation of aldehydes. The nickel-catalyzed reactions of 1,2-bis(dimethylsilyl)carborane 11 with aldehydes such as isobutyraldehyde, trimethylacetaldehyde, hexanal, and benzaldehyde afforded 5,6-carboranylene-2-oxa-l,4-disilacyclohexane.32 34 36 The dehydrogenative 1,4-double silylation of methacrolein and tram-4-phenyl-3-buten-2-one in the presence of a catalytic amount ofNi(PEt3)4 also took place under similar conditions. In contrast, the reaction of 11 with a-methyl-tran.s-cinnamaldehyde and irans-cinnamaldehyde under... 

Methylcarborane [l-methyl-l,2-dicarbaclovododecaborane-(12)] may be prepared by hydrolysis of the Grignard reagent formed from the reaction of (bromomethyl)carborane with magnesium in the presence of diethyl ether.2c B h... 

After the addition of methyl iodide, the solution is heated to the reflux temperature for an additional 3 hours. The reaction mixture is allowed to cool to room temperature and it is slowly added with stirring to about 400 ml. of chilled dilute (IN) hydrochloric acid. The mixture is placed in a separatory funnel, and the carborane is extracted first with 250 ml. of diethyl ether... 

The selective basic degradation of 1,2-dicarbaclovodode-carborane(12) and its C-methyl and C-phenyl derivatives has been recently reported.3 The ethanolic potassium hydroxide degradation of C, C"-dimethyl-l, 2-dicarbaclovododecaborane (12) and the isolation of the trimethylammonium salt of the resulting B9C2Hio(CH3)2 anion are described here as an illustration of this general reaction. The properties of the trimethylam-... 

Fig. 18a. 10. Chemical structures of ion exchangers used in polymeric membranes of ion-selective electrodes with preference toward ions as indicated, (a) Tetraphenyl borates anion exchanger, (b) tridodecyl methyl ammonium chloride cation exchanger and (c) newly introduced carborane cation exchanger.

In solution, the TPFPB salt of the methyl-substituted vinyl cation 19 has only limited stability. Decomposition into unidentified products took place during several days. In contrast, the steric and electronic effects provided by the /-butyl substituent confer indefinite stability to the vinyl cation 20 in the absence of nucleophiles. That is, according to the NMR experiments, a solution of 20 TPFPB in benzene showed no sign of decomposition even after weeks at room temperature. With the carborane anion [CBnH6Br6] suitable crystals for... 

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