Showing papers on "Carborane published in 1984"

Two-dimensional boron-11−boron-11 nuclear magnetic resonance spectroscopy as a probe of polyhedral structure: application to boron hydrides, carboranes, metallaboranes, and metallacarboranes

Abstract: Une technique generale est mise en œuvre pour la determination directe des connectivites bore-bore dans tous les types de composes cages du bore, basee sur la spectroscopie RMN 11 B- 11 B a deux dimensions correlee en J. Discussion des resultats obtenus par cette methode

Transition-metal-promoted reactions of boron hydrides. 6. Platinum(II) bromide catalyzed borane and carborane dehydrodimerization reactions: a new synthetic route to boron-boron linked multicage boranes and carboranes

Abstract: : Platinum dibromide has been found to be a general dehydrodimerization catalyst for boron-boron linked polyhedral cage compounds. The reactions of a variety of small cage systems were explored, and all coupling reactions were found to proceed at moderate temperatures, were highly selective, and gave excellent yields of linked-cage products. These techniques have been used to prepare a number of new coupled cage boron hydrides and carboranes, including 1:1'-B4H92, 1:2'-B4H9B5H8, 1:2'-B4H91'-CH3B5H7, 1:2'-2-CH3B5H73'-CH3B5H7, and 2:2'-1,6-C2B4H52, as well as to provide synthetic routes to the previously known compounds, 1:2'-B5H82 and 2:2'-1,5-C2B3H42.

Rearrangement of Closo-3,3-(PPh3)2-3-H-1-(R)-3,1,2-IrC2B9H10 to Closo-2,2-(PPh3)2-H-8-(R)-2,1,8-IrC2B9H10. Synthesis and X-Ray Structure of Closo-2,2-(PPh3)2-2-H-8-(C6H5)-2,1,8-IrC2B9H10.

Abstract: : During the continuing investigation of the chemistry of the known alkene hydrogenation and isomerization catalyst, closo-3,3-(PPh3)2-3-H-3,1,2-RhC2B9H111 (Ia), the iridum congener and its derivatives, closo-3,3-(PPH3)2-1-(R)-3-H-3,1,2-IrC2B9H10, R = H (IIa)1, R = C6H5 (IIb)2, R = CH3 (IIc)2 and R = 1'-(closo-1,2-C2B10H11) (IId)2 were prepared and notable differences between the reactivity of the Rh and Ir systems were observed. Syntheses of IIb-d, the exo-nido complexes derived from these compounds, and the dimeric complex derived from IIa will be reported in a future paper. Although thermally induced migration of carbon atoms over the surface of polyhedral cobaltacarboranes is a well-established phenomenon, 3 similar isomerization reactions are not so well known for other metallacarboranes. The formation of 2,1,8 isomers of icosahedral metallocarboranes have been observed previously 3 only during high temperature vapor phase thermal isomerization of (n-C5H5)Co(C2B9H11) isomers. The 2,1,8 isomer of this system was observed as the dominant kinetic product (74%) arising from the 3,1,2 isomer during such reactions at temperatures near 500 degrees C; however, three other isomers were also detected in the reaction mixture. Here we report the ready polytopal rearrangement of IIb and IIc under mild thermolytic conditions in toluene solvent at the reflux temperature.

The development of carborane-siloxane polymers

Abstract: Preparation de polymeres repondant a la formule: (Si(R 2 )mCB 10 H 10 CSi(R 2 )-O-Si(R 2 )-O) m . Vulcanisation. Proprietes des vulcanisats

Use of nuclear magnetic resonance to investigate bonding interactions between quadrupolar nuclei: boron―boron spin―spin coupling constants in linked polyhedral borane and carborane cages

Abstract: Etude RMN detaillee d'une serie de boranes et carboranes: [B 5 H 8 ] 2 , [C 2 -2,4B 5 H 6 ] 2 , [C 2 -1,5B 3 H 4 ] 2 et [CH 3 -1B 5 H 7 ] 2

The synthesis and reactions of an anionic tungsten-carbyne complex-stabilised by the carbaborane ligand 1,2,C2B9H9Me2; evidence for a novel cage hydroboration reaction

Abstract: The salt [N(Ph3)2][W(CR)(CO)2(η5-1,2-C2B9H9Me2)](R = C6H4Me-4) reacts with the compounds [RhCl(PPh3)3], [Rh(PPh3)2(diene)][BF4](diene = cyclo-octa-1,5-diene or norbornadiene), and [AuCl(PPh3)] to give products with tungsten–rhodium or tungsten–gold bonds, the structures of which were determined by X-ray diffraction; that from the norbornadiene complex contains a nortricyclane moiety bonded to a boron atom of the C2B9 cage.

Structural study of compounds modelling elementary polymer units, 1. Molecular and crystal structures of 1,3,5-tris(4-biphenylyl)-benzene and 1,3,5-tris[4-(C-o-carboranylmethyl)phenyl]benzene

Abstract: For elucidating the structural features of elementary units of polyphenylene type polymers, prepared by polycondensation of di- and mono-acetylaromatic compounds, and X-ray study of two model compounds was performed, viz. 1,3,5-tris(4-biphenylyl)benzene (1) and 1,3,5-tris[4-(C-o- carboranylmethyl)phenyl]benzene (2) (diffractometer: R = 0,063 (1) and 0,061 (2))· 1 0,5 C6H6 crystals were found to be rhombohedral, a = 20,168 (3), c = 13,678 (3) Ǎ, space group R3c, Z = 6;2· CHCl3 crystals are triclinic, a = 15,7528 (2), b = 12,7004 (6), c = 15,460 (2) A, α = 109,97(1) β = 111,92(1) γ = 100,69 (2) °, space group P1, Z = 2. In the crystal the molecule 1 has a 32 symmetry with a propeller-like orientation of the biphenyl fragments with respect to the central ring (the rotation of the disubstituted benzene rings relative to the central one is 47,2° and relative to the therminal ones, it is 35,9°). In2 the disubstituted benzene rings are rotated with respect to the central one by different values (dihedral angeles are 31,7 - 30,7, and 52,5°). In all benzene rings of both molecules a decrease of the endocyclic bond angles at the ipso-atoms is observed which in 2 depends on the dihedral angeles between the planes of bonded benzene rings. All there carboranylmethylphenyl fragements in 2 have the same conformation: the CH-group of the carborane skeleton “hangs” over the benzene ring plane. The crystal packing of 1and 2 is characterized by sufficiently large cavities which are occupied by solvent molecules. In crystals of 2 the carborane parts of the molecules are associated into separate structural motives.

Degradative insertion reactions of nido-7,9-C2B9H–12.Synthesis and properties of 4-thia -6,8-dicarba-arachno-nonborane (10),4,6,8-SC2B6H10

Abstract: The reaction of 7,9-C2B9H–12(1)with NaNO2and Na2SO3in dilute hydrochloric acid affords 6,8-C2B7H13(2)and the new thiacarbaborane 4,6,8-SC2B6H10(3)the structure of which is proposed on the basis of 1H and 11B n.m.r. spectra.

Carborane reductive-elimination reaction from a six-coordinate hydridocarboranyliridium(III) complex: kinetic and mechanistic study

Abstract: Etude de l'elimination du carborane du complexe Ir(H)Cl(σ-carb)(CO)(PPh 3 ) 2 ; il y aurait dissociation preliminaire donnant Ir(H)Cl(σ-carb)(CO)(PPh 3 ) qui subit une elimination reductrice de la molecule carborane par 2 voies

Synthesis of heterocyclic compounds containing four carbon atoms of two o-carborane systems, a silicon atom, and a Ni, Co, Pd, or Cu atom in the ring

Abstract: The reaction of bis[lithium(o-carboranyl)]dimethylsilane with α, α′-dipyridyldichloride complexes of Ni, Co, Pd, and Cu gave heterocycles containing a silicon atom, four carbon atoms of two o-carborane systems and a transition metal in the ring. These compounds were more stable than the corresponding acyclic o-carborane σ-complexes.

Cyclopalladation of carborane tertiary amines

Abstract: Starting from, tertiary amines of the carborane series, cyclic complexes with σ B-Pd bonds have been obtained, which give insertion products with two molecules of diphenylacetylene, at the B-Pd bond.

A new simple method for the production and some conversions of boron‐sulfur bond‐containing o‐ and m‐carboranyl

Abstract: A new method of synthesis of o- and m-carboranyl-B-thiols and o- and m-carboranyl-B,B'-dithiols via the electrophilic sulfuration of o, m-carboranes with S2Cl2 in the presence of AlCl3 is described. The reaction of o-carborane with excess S2Cl2 in the presence of AlCl3 gives B,B',B″,B″′-tetrathiol-o-carborane. Various chemical conversions of carborane sulfur derivatives are studied. A description is made of carboranyl derivatives of di-, tetra- and hexavalent sulfur, such as sulfenyl chlorides, thiocyanates, disulfides, alkyl- and aryl sulfides, aryl sulfones and aryl sulfoxides. 9-m-Carboranylsulfinic acid was found to readily disproportionate to thiosulfonate and sulfonic acid. The chemical behaviour of o- and m-carboranyl sulfur derivatives in which the sulfur atom is σ-bound to the six-coordinated boron atom was also found to be similar to that of organic sulfur derivatives.

Catalysis with metallacarboranes

Abstract: The formal 18 electron rhodium(+3) cluster, closo-3, 3-(PPh3)2-3-H-3, 1, 2-RhC2B9H11 (I) and related species are useful catalysts for alkene isomerization, hydrogenation and other reactions under mild conditions. These results appear to be anomalous in view of the stable electron configuration of the rhodium center present in (I). Resolution of this conflict was obtained by the observation that alkyl substitution at both carborane cage carbon atoms of (I) resulted in the isolation and structural characterization of several catalytically active formal 16 electron rhodium(+1) nido-species. The fact that these isolated nido-clusters display all of the kinetic characteristics of closo-(I) in alkene isomerization and hydrogenation reactions suggests that closo-(I) is in equilibrium with a spectroscopically invisible and catalytically active nido-tautomer of similar structure. The proposed general mechanism of alkene isomerization and hydrogenation incorporates this view and is further supported by kinetic studies coupled with isotopic labeling experiments, synthesis and crystallographic results.

Electrical properties of pyrolysis products of the carborane-containing polyarylates☆

Abstract: The method of electrical spectroscopy has been used to investigate the electrical conductivity of solid products of pyrolysis formed during heat treatment of a carborane-containing polyarylate. A major structural reorganization occurs in the samples under heating, whereby extensive regions of aromatic ring structures are formed.