Methanide derivatives

Another way to describe this non-cyclic phosphino methanide derivatives consists of theuse of monodentate complexes with themono-oxide [203] or monosulfide [204] dppm giving the methanide or methanediide derivatives (14) after addition of the appropriate amounts of [Au(acac)PPh3[. A mixed-valence Au(I)-Au(III) can be isolated by coordination of the fragment AuPPh3 to the free sulfur atom in the mono-oxide starting material [204]. 

A five-membered methanide auracycle [Au(C6F5)2(SPPli2CFl2PPh2)]C104 (25) is described with the monosulfonated dppm, obtained after chlorine elimination of [Au (C6F5)2Cl(SPPh2CH2PPh2)j with a silver salt. After deprotonation of the methylene group (26) and later coordination of additional metal centers affords dinuclear and trinuclear methanide derivatives (27, 28) [210]. 

Fernandez, E.J., Gimeno, M.C., Laguna, A., Lopez-De-Luzuriaga, J.M. and Olmos, E. (1998) Two alternatives for the synthesis of non-cyclic phosphino-methanide derivatives of gold. Polyhedron, 17(22), 3919-3925. 

Complexes with mixed C,P or C,As donor ligands are derived of ortho-metalated phosphines or arsines or of methanide derivatives. The dinuclear complexes [Au2(C6F[3-2-EPh2-6-R)2] (E = P (589), As R = H, Me) are obtained by reaction of 2-EPh2-6-R-C6F[3Li with [AuBr(PEt3)] at —70 °c.2002 2004,20 6 The treatment of the dimer [Au2(C6Fl4PPh2)2] with methyltriflate yields, unexpectedly, [Au5(C6Fl4PPh2)4]+.3134 The mixed dinuclear derivative [Au2(5-Me-C6H3-2-... 

Another triflate ester that recently has found growing application in organic synthesis is commercially available trimethylsilylmethyl trifluoromethanesul fonate. This powerful alkylating reagent can be used for the synthesis of various methylides by an alkylation-desilylation sequence A representative example is the generation and subsequent trapping by 1,3-dipolar cycloaddition of indolium methanides from the corresponding indole derivatives and trimethylsilylmethyl trifluoromethanesulfonate [108] (equation 54)... 

Very few examples of bridging non-cyclic methanides of gold are known. Among them the complex 79 has been reported as the result of the reaction of phosphine-phosphonium derivatives with acetylacetonate derivatives of gold(I) [103,104]. The complexes 80 [89,98], already seen in previous paragraphs, cor-... 

Elimination of the chlorine atom from [Au(C6E5)2Cl(dpma)] [29] with AgC104 gives the corresponding chelate bis(diphenylarsine)methanegold derivative, which evolves to the methanide [Au(C6F5)2(Ph2AsCHAsPh2)] under deprotonation reaction with NaH. 

The presence of an excess of electron density on the carbon atom in methanide gold (III) complexes permits them to act as C-donor nucleophiles forming dinuclear or even polynuclear derivatives. 

Thus, the abstraction of the chlorine atom in [Au(QF5)2Cl(dppm)j [175] provides a mononuclear gold(I II) derivative with the diphosphine acting as a chelate ligand, which is an excellent starting material in the synthesis of dinuclear or polynuclear methanide and methanidiide complexes after deprotonation of the dppm ligand (first deprotonation with HNa and the second with acetylacetonate gold(I) derivatives) [198-201] (Scheme 3.3)... 

Laguna, A. and Laguna, M. (1990) Bis (Diphenylphosphino)Methanide Or Bis (Diphenylphosphino)Methamide And Its Derivatives As Ligands In Gold Chemistry - A Review. Journal of Organometallic Chemistry, 394(1-3), 743-756. 

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. 

In the reactions with phosphonio-a-methoxycarbonyl-alkanides, the products of type 261 derived from 1,3-cycloaddition can rearrange to the tautomeric lif-pyrazolo-triazole (87MI2). The reaction of 3-diazopyra-zoles and 3-diazoindazole with acyl-substituted phosphonium ylides led to pyrazolo-triazine and indazolo-triazine derivatives 266 instead of the expected triazole compounds (8IJHC675). In this case, the ylides, which can exist as phosphonium enolates, possess nucleophilic and electrophilic centers in a /8-relationship, giving [7 + 2] or [11 -I- 2]cycloaddition reactions. With dimethylsulfonio-a-aroyl-methanides, very complex, temperature-dependent mixtures were obtained, in some cases with sulfur retention (87MI3). 

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