Tris methanide

Kuhn s carbanion, the all-hydrocarbon anion tris(7//-dibenzo[c,g]-fluorenylidenemethyl)methanide ion [2 ] (Kuhn and Rewicki, 1967a,b), is a stabilized system with tt electrons widely spread over the sp hybridized carbon framework, and was isolated as the potassium salt. It also appears in DMSO solution by dissolving the parent hydrocarbon, resulting in a deep green colour. The pKg value of the precursor hydrocarbon [2]-H is 5.9 in aqueous HCl-DMSO (Kuhn and Rewicki, 1967a,b), and its enormous stability, as compared with cyclopentadiene [9]-H, pKa 18 in DMSO... 

In view of the ease of dissociation of the a bond into resonance-stabilized hydrocarbon ions, it is expected that an authentic hydrocarbon salt could be isolated from an extraordinarily stable cation and anion. The first synthesis of a salt composed solely of carbon and hydrogen was achieved on the combination of tris(3-guaiazulenyl)cyclopropenylium ion [1" ] and tris(7//-dibenzo[c,g]fluorenylidenemethyl)methanide ion [2 ] (Okamoto et al., 1985). 

Jones, P.G. (1992) [(Methyldiphenylphosphonio)methanide] tris(pentafluorophenyl)gold(III) acetone solvate. Acta Cr/staUographica, Section C Crystal Structure Communications, C48(7), 1209-1211. 

Some particular aspects of the chemistry of ylides as ligands have been reviewed throughout the years [15-27]. The topics are quite specific in most cases, and are mainly treated comprehensively nonstabilized ylides [15, 16], S-ylides [17], Au ylides and methanides [18], Li derivatives [19], Pd and Pt complexes [20-23], zwitterionic metallates [24], stabilized ylides [25], and applications [26, 27] have been reported upon. We will try in the following sections to give a basic complementary point of view about the chemistry of ylides as ligands. 

Iridium complexes with O-donor ligand environments, Ir(triso)(ol)2 [triso = tris(diphenyloxophosphoranyl)methanide ol = C2H4, cyclooc-tene), catalyze the hydrosilylation and dehydrogenative silylation of ethylene with triphenylsilane.35 Diphenylmethylsilane can also be used in the... 

Ketones and tertiary alcohols were also available in good yields under mild conditions through interaction of trialkylboranes with lithium tris(phenylthio)methanide followed by oxidation [285],... 

Lithium tris(phenylthio)methanide, LiC(SC6H5)3 (1). This anion of Iris(phenythio)methane1 is prepared with n-butyllithium in THF at —78°. 

Sarsfield reported the only three known examples of uranyl bis(imino-phosphorano)-methanides reported to date.52,53 Treatment of the tris-THF adduct of anhydrous uranyl dichloride with one molar equivalent of 2 resulted in the isolation of dimeric 101 when the recrystallisation was carried out in dichloromethane, but monomeric 102 when recrystallised from THF. Both 101 and 102, when treated with two and one equivalents, respectively, of potassium bis(trimethylsilyl)amide afford 103. Complexes 101-103 all exhibit uranyl-methanide contacts in the solid state and these represent noteable examples of out-of-equatorial-plane uranyl coordination. A DFT study concluded that the methanide centre coordinates to the uranyl centre with an orbital of p-type character by a highly polarised cr-type interaction. 

A successful study of non-phosphine iridium complexes Ir", Ir , and Ir e. g., IrX(cod)2 [60], IrH2(triso)(SiMePh2)2 [61, 62], Ir(triso)(coe)2 (coe = cyclooctene triso = tris(diphenyloxophosphoranyl)methanide), Ir(triso)(C2H4)2 [61], has demonstrated effective hydrosilylation of alkenes and alkynes. Iridium phosphine complexes, e. g., Ir(C=CPh)(CO)2PCy2 [63] and IrCl(CO)(PPh3)2 [64], are also found to be active for hydrosilylation of phenylacetylene and 1-hexyne. 

A related compound scandium tris(trifluoromethylsulphonyl)methanide, Sc[(F3CS02)3C]3 (scandium triflide) has been prepared and used as a catalyst in the nitration of o-nitrotoluene.209 Scandium triflide has proved to be a better catalyst than scandium triflate for the aromatic nitration of the electron deficient o-nitrotoluene. 

Similarly, the Iricyclopropylcyclopropenylium ion (23) reacted in chloroform with the tris(7/7-dibenzo[c ]fluorenylidenemethyl)methanide ion (24), which is known as the most stable allhydrocarbon carbanion, to give a covalent cyclopropene 25, which was directly observed by NMR spectroscopy but could exist only in solution evaporation or cooling of the chloroform solution of 25 afforded the heterolytically dissociated salt 23 24 quantitatively. In a polar solvent such as dimethyl sulfoxide the salt dissolved to give the free ions. As far as the reaction in tetrahydrofuran/acetonitrile was concerned, cyclopropenylium ions 26 (X = 4-Cl, H) reacted with carbanion 24 to give the covalent cyclopropene 27, whereas the slightly more stable cations 26 (X = 3-Me, 4-Me, 4-OMe) gave the completely ionized salts, the so-called hydrocarbon salts . The most stable cyclopropenylium ions 28 (pATr in 50 /o aqueous acetonitrile > 10) and 27 (pA t 8.9) also afforded the ionic salts under similar conditions. ... 

Li TFSI Lithium bis(trifluoromethane sulfonyl) imide Li TriTFSM Lithium tris(trifluoromethyl sulfonyl) methanide... 

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