Ylide complexes of gold

Ylide complexes of gold are unique in that they exhibit an exceptional chemical and thermal stability, which facilitates preparative and structural work very considerably. It was in this class of compounds that a large variety of true organogold(ll) and mixed valence organogold(l)/(lIl) complexes was discovered. These are rare in the remainder of organogold chemistry. 

There now exists a large number of methods for the synthesis of organogold complexes with various ylide ligands. In an extensive reaction chemistry, successive oxidation of the gold centres [Au(I) -> Au(II) Au(III)] can often be accomplished. Ylide complexes of gold have therefore been summarized in the following sections regardless of their oxidation state. 

Mononuclear ylide complexes of gold(I) and gold(III) have been obtained in a variety of ways203,204, as detailed below. The largest number of complexes of both gold(I) and gold(III) has been prepared with phosphorus ylides, but species containing arsenic or sulphoxonium ylides have also been reported. Some prototypes are summarized in Table 7. 

TABLE 7. Mononuclear ylide complexes of gold(I) and gold(III)... 

The reaction chemistry of both mono- and bis(ylide) complexes of gold(l) has been explored for several cases. In carbonyl-stabilized yhde ligands, the acidic proton of the a-methylene group can be replaced by yet another gold(I) unit leading to polynuclear... 

Schmidbaur. H. Hartmann, C. Reber. G. Muller, G. Isovalent and mixed-valent ylide complexes of gold The synthesis of trinuclear compounds having double paddle-wheel structure. Angew. Chem.. Int. Ed. Engl. 1987. 26. 1146. 

Gold(I) ylide complexes of various types have been prepared (45). Reactions of [AuCIL] complexes with ylides led initially to monoylide species (49), but displacement of L also occurred with excess ylide [Eq. (16)]. Analogous compounds with one or two a-silyl groups were also obtained. 

Six gold(I) ylide complexes of the types described above have been tested for use in arthritis therapy (55), but only one showed an activity comparable to standard chrysotherapeutic agents. The separation between toxic and therapeutic doses was too narrow, but this is clearly an area where further study could be of immense value. 

The use of ylides as ligands has allowed a number of gold(III) complexes containing four organic groups to be isolated. A review of ylide complexes of several transition metals, including gold, has appeared (48), and such species were featured briefly therein. 

D. Complexes of Gold , Gold ) and Gold(III) with Ylide Ligands. . . 251... 

Hubert Schmidbaur, Andreas Grohmann, M. Elena Olmos and Annette Schier of bis(ylide) complexes of monovalent gold (equation 53)227. 

The compound 70 has also been reported showing the ambident character (both C- and N-coordination) of the cyano-stabilized ylide as ligand. The authors have also transposed their work concerning the keto-bis-ylide and palladium, with the synthesis of the C-bonded complex 71 or the new cycloplatinated or-thometallated compound 72. The latter by various treatments allows one to obtain other ylidic cationic complexes of platinum such as 73. A C,C,C-terdentate coordination of the keto bis-ylide, already observed with the palladium is also obtained from the reaction of 73 with gold derivatives. 

The behavior of Hg(CN)2 toward the dinuclear gold(I) amidinate complexes requires comment. In the case of the dinuclear gold(I) ylide, oxidation of the Au(I) to Au(II) resulted in the formation of a reduced mercury(O) product. Figure 1.19(a) [36]. In the mercury(II) cyanide reaction with the dinuclear gold(I) dithiophosphinate. Figure 1.19(b), the stability of the gold(I)-carbon bond compared... 

Uson, R., Laguna, A., Laguna, M. and Uson, A. (1983) A new route for the synthesis of gold(I) and gold(III) pentafluorophenyl(ylide) complexes. Inorganica Chimica Acta, 73(1),... 

Trzcinskabancroft, B., Knachel, H., Dudis, D., Delord, T.J. and Marler, D.O. (1985) Experimental And Theoretical-Studies Of Dinudear Gold(I) And Gold(II) Phosphorus Ylide Complexes - Oxidative Addition, Halide Exchange, And Structural-Properties Including The Crystal And Molecular-Structures Of [Au (CH2)2PPh2]2 And [Au(CH2)2PPh2]2(CH3) Bri. Journal of the American Chemical Society, 107(24), 6908-6915. 

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