Showing papers on "Carborane published in 1981"

Metallocarborane precursor and catalyst

Abstract: IMPROVED METALLOCARBORANE PRECURSOR AND CATALYST Abstract of the Disclosure: An extraordinarily active carborane catalyst for use in hydrogenation, hydroformulation and isomerization reactions. The new catalyst is a modification of known metallocarborane catalysts having a transition metal symmetrically bonded to the pentagonal face of a dicarborane cage with two triphenylphosphine ligands and one hydrogen ligand occupying the remaining transition metal ligand sites. The new alkene-metallocarborane replaces one of the triphenylphosphine ligands with a lower chelating or bridging alkene which is bound to both the transition metal and the carborane cage. The alkene-metallocarborane catalyst may be used as a homogeneous catalyst or may be bound to a suitable polymer support for use as a heterogeneous catalyst. The catalyst has been found to be among the most highly reactive catalysts known to date. It is believed the high reactivity of the new catalyst is due to the in situ irreversible hydrogenation of the alkene side chain to produce an open coordination site on the transition metal atom.

Synthesis of five-membered heterocycles containing in the ring two carbon atoms of an o-carborane ring, two methylene groups, and atoms of Ni, Pd, Pt, Ti, Zr, Si, Ge, OR Sn

Abstract: 1. Stable five-membered heterocycles, including in the ring the two carbon atoms of an o-carborane nucleus, two methylene groups, and Ni, Pd, Ft, Ti, or Zr atoms have been obtained when l,2-di(bromomagnesiummethyl)-o-carborane reacts with (PPh3)2MCl2, where M=Ni, Pd, or Pt, and with (C6H5)2MCl2, where M=Ti or Zr. 2. When 1,2-di(bromomagnesiummethyl)-o-carborane reacts with MX4, where M=Si, Ge, or Sn and X=Cl, five-membered compounds are obtained with-a spirostructure with rings which include two carbon atoms of the o-carborane nucleus and an atom of Si, Ge, or Sn.

The synthesis and study of polyphenylene-type polymers based on the ethylketals of diacetylarylenes and acetyldiphenylyl-o-carborane☆

Abstract: Soluble polyphenylene-type prepolymers have been synthesized by polycondensing the ethylketals of acetyl-aromatic compounds based on that of acetyldiphenyl- o -carborane. Their heat treatment has led to the production of cross-linked systems. The synthesis conditions for these prepolymers have been optimized; it was found that a reduction of the proportion of dipnone fragments in the carborane prepolymers improved the heat resistance of the final products.

Influence of carborane-containing compounds on the oxidative stability of products of pyrolysis of network polymers

Abstract: A study has been made of the influence of o -carborane and its aryl derivatives on the oxidative stability of the products of pyrolysis of synthetic thermoreactive polymers. It is shown that o -carborane increases the oxidative stability of the pyrolysis products more efficiently that phenyl- or diphenyl- o -carborane.

Reaction of symmetrical derivatives of B-mercurated carboranes with nucleophilic reagents

Abstract: The B-Hg bond in symmetrical B-mercurated carborane derivatives is resistant to the action of nucleophilic reagents such as LiAlH4, BuLi, and C10H6·−Li+.

IR spectroscopy for quantitative determinations of the structural unit heterogeneity of carborane-containing polyoxyamides

Abstract: The structural unit type of heterogeneity of m - and p -carborane-containing polyoxyamides synthesized by the nonequilibrium polycondensation of dichlorides of m - and p -carborane dicarboxylic acids and bis-( o -aminophenols) has been evaluated quantitatively under various conditions, using the method of IR analysis. Quantitative determinations were based on the bands at 1760 cm −1 (ν CO of the ester bond) and 2600 cm −1 (ν BH in the carborane ring, used as an internal standard). It is shown that the macromolecular composition of polyoxyamides prepared under various conditions may contain units of both linear (A) and branched (B) structure, viz. , with the n/m ratio ranging from 1 : 0 to 0 : 1.

Homopolymerization of carborane exocyclic vinylsilanes and their copolymerization with methyl methacrylate

Abstract: A study has been made of the homopolymerization of carborane exocyclic vinylsilanes having the vinyl group and various substituents (CH3, OCH3, Cl) at the silicon atom. These compounds were polymerized in bulk, using benzoyl peroxide and tert-butyl peroxide as initiators. Under like conditions the compounds were copolymerized with MMA, varying the ratio of the initial monomers. It was found that homopolymerization and copolymerization with MMA in some cases involves vinyl group participation, and is accompanied by partial ring opening. This results in the formation of crosslinked polymers containing boron and silicon.

Kinetics and mechanism of thallation of carboranes

Abstract: 1. The pseudo-first-order reaction rate constants for the thallation of substituted carboranes were determined. 2. The thallation rate of methyl-o-carborane is second order in thallium tris(trifluoroacetate) and first order in carborane.

Boranametallacarboranes. 1. Synthesis and Characterization of (Borane) Cobalt (Carborane) Sandwich Complexes

Abstract: : The first known examples of borane-metal-carborane sandwich complexes, in which a metal atom simultaneously occupies vertices in a metallaborane and a metallacarborane framework, have been obtained from reactions of B5H8- or B9H14- ions with CoCl2 in THF, followed by addition of R2C2B4H5- ion (R = CH3 or C2H5). With B5H8- and (C2H5)2C2B4H5-, the characterized products are (2,3-(C2H5)2C2B4H4)-2-Co-(B5H10) (I), (2,3-(C2H5) 2C2B4H4)-5-Co(B9H12-1-0(CH2)4) (II), and (2,3-(C2H5)2C2B3H5)-5-Co(B9H12-1-0(CH2) 4) (III). With B9H14- as the borane reagent, the products are (2,3-(C2H5) 2C2B3H5)-6-Co-(B9H12-2-0(CH2)4) (IV) and (1,2-(C2H5)2C2B7H7)-6Co-(B9H12-2- 0(CH2)4) (V), as well as traces of I, II, and III. Except for I, an orange oil, all products are crystalline solids.

Reactions of 4-(o-carboranyl)pyrylium salts with nucleophilic agents. Synthesis of nitrogen heterocycles with an o-carboranyl substituent

Abstract: Nitrogen heterocycles, viz., pyridines, pyridinium salts, diazepine, and pyrazoles, with an o-carboranyl substituent were obtained by reaction of 4-(o-carboranyl)-pyrylium perchlorates with nitrogen-containig nucleophilic agents, viz., ammonia, primary amines, hydrazine, and phenylhydrazine. Opening of the pyrylium ring without involvement of the carborane ring occurs under the influence of bases.

Low temperature transformations of polyarylates containing carborane

Abstract: A study was made of the behaviour of polyarylates containing carborane under conditions of low temperature degradation. Regularities of the formation of cross-linked three-dimensional structures were examined using sol-gel analysis. It was shown that in vacuum and in the presence of oxygen carborane particles forming BOB molecular bonds take part in crosslinking of polymer chains. Using studies of gel-formation in polyarylates containing carborane, conditions were proposed for heat treatment in order to improve mechanical properties of polymers.

X-ray diffraction study of C-monosubstituted derivatives of o-carborane with trimethylsilyl and trimethylgermyl substituents

Abstract: 1. The data of a detailed x-ray-diffraction study of 1-trimethylsilyl- and trimethyl-germyl-o-carboranes show that the Si-C and Ge-C bonds between the carborane ring and the substituent are larger than the bonds in the substituent itself, and CH3 groups have a screened orientation with respect to the unsubstituted C-atom of the o-carborane skeleton. 2. The electron-deficient carborane ring appreciably influences the geometrical parameters of the bond of the polyhedron C atom with substituents.