Nickel complexes carborane

Quite a number of silylnickel and silylenenickel compounds have been reported, and only a few can be cited here2305-2309 Bis(silyl)nickel complexes have been implicated as important intermediates in Ni-catalyzed double silylation of various organic substrates. Using an o-bis(dimethylsilyl)carborane ligand, complex (930) could be isolated and structurally characterized 2310 Its unusual thermal stability is attributed to the advantageous steric and electronic properties of the carboranyl unit. (930) undergoes... 

Curiously, only chromium (33), cobalt, and nickel complexes of this 11-atom ligand have been prepared thus far. The complex (l,7-B9C2Hu)2Co has been prepared by both the anhydrous and aqueous methods (18). An X-ray diffraction study of the cesium salt of the cobalt(III) complex confirmed the symmetrical sandwich bonding of the carborane cages but failed to locate the carbon atoms because of disorder in the crystal (48). 

Polystyrene supported nickel(II) carborane complexes 44a and 44b have been tested in the polymerisation of ethylene, styrene and vinyl chloride in [C4Ciim][BF4], The compounds were active for all three substrates, even in the absence of a co-catalyst. Increased catalytic activity was observed relative to THF, affording polymers with higher molecular weight and, in most cases, lower polydispcrsity.1671... 

The reaction of alkynes withl,2-bis(dimethylgermyl)carborane 196 in the presence of a catalytic amount of the nickel complex 197 gives a range of carborane substituted 1,4-digermacyclohexenes 198, in good yield, as shown in Scheme 50 <2002OM3922>. 

Flgui 3.13. iVido Carboranes as ligands in a nickel complex that can undergo two reduction reactions. 

An increasing volume in the literature is devoted to pseudo-cyclopentadienes and pseudo--arenes. A general paper describes complexation of the cyclo-Ps anion. The synthesis of the first diazacobaltocene has been described. Tert-butyl-substituted diazaferrocenes have been prepared from substituted pyrroles. Bis-(borole)nickel complexes have been prepared from dilithium txnelediides. Carborane stabilised iron indole and iron thiophene complexes have been made. The electrophilic stacking of borataferrocene and bis(borole)cobaltate ions with -Cr(CO)3 and Mn(00)3 has been described. The synthesis and crystal structure of... 

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... 

Dimethyl bis-benzamidinato complex, with Ti(IV), 4, 344 Dimethyl carboranes, with tantalum, 5, 163 Dimethyl complexes with cadmium, 2, 464 with nickel, 8, 58-59 with platinum(II), 8, 460 with titanium(IV), 4, 331, 4, 343 Dimethyl diallylmalonate, cyclization-hydrosilylation, 11, 385 Dimethyl diamido complexes, with Ti(IV), 4, 332... 

The double silylation of unsaturated organic compounds catalyzed by group 10 metals is a convenient synthetic route to disilacyclic compounds. Nickel and platinum complexes, in particular, are excellent catalysts for the transformation of disilanes. Cyclic bis(silyl)metal complexes2,3 have been implicated as key intermediates in the metal-catalyzed double silylation of alkynes, alkenes, and aldehydes however, the intermediates have not been isolated due to their instability. We now describe (i) the isolation of the reactive intermediates cyclic bis(silyl)metal compounds (1) with bulky o-carborane unit 4 (ii) the generation of a new class of heterocyclic compounds (4-5) by the stoichiometric reaction of the intermediates with a variety of substrates such as an alkyne, dione, and nitrile 4 and (iii) the facile double silylation of alkenes and alkynes (10,12-14) catalyzed by the intermediate under mild conditions.5... 

Carborane-metal complexes, 8, 87-113 Catalysis by organometallics carbonylation, 6, 158-163 hydroformylation, 6, 128-136 olefin reactions, 7, 199-202 organic syntheses by nickel compounds, 8, 48-83 reviews, 10, 331-336 Cationic metal carbonyls, 8, 117-159 Chromium carbonyls, 8, 133-159, see also Benchrotrenes Cobaloximes, 7, 161, 203 Cobalt carbonyl, 6, 119-163 8, 152-155 Cotton-Kraihanzel method, 10, 213-214 Coupling reactions, on nickel, 8, 30-39, 82-83... 

Zirconacycles are in general much more stable than their nickel analogs and often serve as very important and versatile intermediates for the construction of the carbon-carbon bond [32], The carborane version of zirconacyclopentenes 1,2-[Cp2ZrC(R)=C(R)]-l,2-C2BioHjo (19) can be obtained by the treatment of complex 9 with various kinds of alkynes (Scheme 7.12) in refluxing toluene [33], This reaction cannot proceed in donor solvents such as Et20 and THF, suggesting that the coordination of alkyne to the Zr atom is essential for the subsequent insertion. 

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