Enolato complexes

Bis[iV,iV -di(2-pyridyl)-imidazol-2-ylidene]aurate(I) tetrafluoroborates, preparation, 2, 292-293 Bis[iV,iV -di(2-pyridyl-methyl)-imidazol-2-ylidene]aurate(I) tetrafluoroborates, preparation, 2, 292-293 Bis(diselenolate) complexes, dinuclear iron compounds, 6, 242 Bis(dithiolene) compounds, in tungsten carbonyl and isocyanide complexes, 5, 644 Bis(enolato) complexes, with bis-Cp Ti(IV), 4, 589 Bis(enones), in reductive cyclizations, 10, 502 Bis(ethanethiolato) complexes, with bis-Cp Ti(IV), 4, 601 Bis(ethene)iridium complexes, preparation, 7, 328-329 -Bis(fluorenyl)zirconocene dichlorides, preparation,... 

Enolato complexes from diketones and their derivatives... 236... 

Empirical observations and calculations suggest that some 2-oxoalkyl complexes rearrange to O-bonded structures in solution (Section n.C, Chapter 6) . This is probably the reason why many authors still name species [M]-CH2C(0)R as C-enolato complexes, although it is both incorrect and confusing. 

As the namre of most enolato complexes in solution is strongly dependent on the solvent and it is not always well established, and the enormous amount of enolato complexes reported exceeds the limits assigned to this chapter, we have restrained its content to the synthesis of isolated, mainly fully characterized, enolato complexes. 

The synthesis of metal enolato complexes will be presented in sections according to the type of reagent supplying the oxygen atom of the enolato ligand and in each section the different types of metals will be considered separately. 

AcMes has been chosen as a model ketone for deprotonation since its enolato complexes have excellent crystallization properties with a variety of cations. Thus, the reaction of AcMes with KHMDS in PhMe gives the type 9 complex [K4 /Z3-OC(=CH2)Mes 4 (PhMe)4] (type 9 and with NaBu-n and tmeda leads to the sodium enolato complex [Na2 /z-OC(=CH2)Mes 2(tmeda)2] (type 8) . 

Complex 23 is an enolising reagent toward aliphatic ketones such as (Bn)2CO, AcCHPh2 or camphor, giving enolato complexes 24. ... 

The syntheses of mixed Na/Mg metal enolato complexes 25-27 (RO = 0(=CH2)Mes) have been reported by mixing the metal alkyl reagents NaBu-w and Mg(w-Bu)2 in the desired stoichiometry with the required amount of AcMes and tmeda . 

The deprotonation of a series of ketones by [Zn2(Ph)2L], where ]J represent varions bis(amidoamine) ligands, gives the corresponding enolato complexes. Their crystal stmc-tures show some of them to be dimers [Zn2 OC(=CR2)2R 2L] (R = Me, R = i-Pr R = H, R = CeMcs). Li enolates of A,A-disnbstitnted glycine esters Me02CCH2N(R)R react with [Zn(Et)Cl] to give 31. ... 

Equimolar amounts of EDA and 48 give the corresponding lithium enolato complex which, by means of a Claisen-type condensation, leads to 49, which, in turn, reacts with [Zr(r 5-Cp)2(Me)Cl] to give 50 1... 

AcPh to give also 59 . Complexes 61a-c react with KOC(=CH2)R to afford enolato complexes 60a, 60b, 60c . The reaction of 61d with KOC(=CH2)CH2Bn-f gives 63, containing a dianionic enolato ligand . 

V. L-Ascorbato complexes. The coordination chemistry of vitamin C has recently been reviewed . There have been few reports on the isolation of ascorbato complexes, and their structures have been the subject of some controversy due to the unstable natnre of the molecule and the hydrolytic instability of complexes. However, L-ascorbic acid (109) reacts with [Pt(OH)2(N N)j (N N = diamines) to give a mixture of the 2,5-dioxoalkyl complex 110 and the enolato complex 111 . 

The Af,0-enolato ligands 146 are usually prepared by deprotonation of the corresponding conjugated acids which, for ketimines, can be formulated as consisting of the tautomeric forms 147-149. However, some of them have been prepared (i) by reacting nitriles with the corresponding S-diketonato complexes, or with 2-oxoalkyl or enolato complexes (Section in.C, Chapter 6 ) or (ii) by oxidation of diketoamines with metal complexes in the presence of a base (Section n.B.3). Although the most abundant tautomeric form of a S-ketimine depends on the nature of the substituents, they wiU be represented as 148. 

The ligands 164 react with NiCl2 H20 and various additional ligands to give enolato complexes 165 °. 

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