Carboxylato complexes

Tetrakis-Cp uranium complexes are readily prepared via metathesis of UCl and KCp in refluxing benzene. These complexes are a relatively rare example of a pseudotetrahedral complex with four Tj -Cp rings, (rj-ring) (25). The Cp derivative has been shown to react with CO and CO2 to give acyl and carboxylato complexes. This complex also reacts with alkyl haUdes to afford the U(IV) complex, Cp UX (X = halide). 

Complexes of cobalt(III) with O-donor ligands are generally less stable than those with Af-donors although the dark-green [Co(acac)3] and M iCo-( 204)3] complexes, formed from the chelating ligands acetylacetonate and oxalate, are stable. Other carboxylato complexes such as those of... 

Relationships between the carbon-oxygen stretching frequencies of carboxylato complexes and the type of carboxylate coordination. G. B. Deacon and R. J. Phillips, Coord.. Chem. Rev., 1980, 33, 227-250 (177). 

Leciejewicz J, Alcock NW, Kemp TJ (1995) Carboxylato Complexes of The Uranyl Ion Effects of Ligand Size and Coordinat. Geometry Upon Molecular and Crystal Structure. 82 43-84... 

Oxidative addition of the O-H bond to transition metal complexes gives hydrido(hy-droxo), hydrido(alkoxo) or hydrido(carboxylato) complexes (Eq. 6.1), but web-characterized complexes obtained as primary products from the reaction of the compound, XO-H (XO-H = water, alcohol, and carboxylic acid) with late transition metals are quite rare [1]. Furthermore, the crystal stractures of very few complexes of this type have been reported. In this section we will survey late transition metal complexes resulting from activation of water, alcohol, and carboxylic acid. 

Preparation of Hydrido(hydroxo), Hydrido(alkoxo), and Hydrido(carboxylato) Complexes by Metathesis... 

Before discussing the preparation of late transition metal complexes resulting from the activation of O-H bonds by late transition metal complexes, we wbl describe metathesis methods for the preparation of hydrido(hydroxo), hydrido(alkoxo), and hydrido(carboxylato) complexes. Though many methods of preparation of transition metal hydroxides, alkoxides, etc. by a metathesis reaction have been reported [1], only a limited number of examples of the preparation of hydrido(hydroxo), hydri-do(alkoxo) complexes etc. by metathesis are available. 

Complexes Resulting from Activation of Carboxylic Acids Hydrido(carboxylato) Complexes... 

Examples of the isolation of hydrido(carboxylato) complexes by oxidative addition of carboxylic acid are very rare. Wilkinson [55] examined oxidative addition of fluoro carboxylic acids to Vaska s complex, trans-[lrCl(CO)(PPh3)2]. They isolated colorless hydrido(carboxylato) complexes of stoichiometry, [lrCl(H)(OCORF)(CO)(PPh3)2] (RE = CE3, C2F5), but did not completely succeed in characterizing the products of the oxidative addition. The complex is claimed to be a mixture of four closely similar... 

The reactivities of several hydrido(carboxylato) complexes of iridium have been studied [58]. Complexes 88 reacted with carbon monoxide to afford carbonyl complexes, [IrCl(H)(OCOR)(CO)(PPh3)2] (98), in which the carboxylato ligands changed to monodentate ligands and exist as a mixture of isomers (Eq. 6.31). 

The authors concluded that steps (ii) and (iii) are certainly fast but that step (iv) must be sufficiently slow for the carboxylato complex to diffuse away from the electrode before CO formation takes place. 

The reactivity of the methyl complexes 14a and 15 with carboxylic acid was examined to provide carboxylato complexes as useful precursors for enzyme models. For example, a slight excess of acetic acid does cleave the Zn-CHa bond by elimination of methane and yields [Zn(bd bpza)02CCH3] (17) (Scheme 16) and [Zn(bpa ) O2CCH3] (18). 

D. Ruthenium Carboxylato Complexes Bearing Bis(pyrazol-1-yl)acetato Ligands... 

The presence of water in the crystals can be explained by humid crystalization conditions and is proven by elemental analysis. The water adduct formation shows, that k 0, 0 -carboxylato ligands are hemilabile, chelating ligands, which can be easily displaced from one coordination site by a solvent. Thus, the carboxylato complexes 37a and 37b are equivalent to 16 VE fragments stabilized by the hemilabile carboxylato complexes. 

Reaction of [Ru(bdmpza)Cl(PPh3)2] (24) with thallium 2-oxocarbox-ylates T1[02CC(0)R] (R = Ph, CH2CH2CO2H) yields k 0 0 -2-oxo-carboxylato complexes (Scheme 24). Single P NMR signals at... 

Table 5 Structural parameters for dinuclear manganese(III)-carboxylato complexes. ...

There are many important mixed valence and fractional formal oxidation state compounds (e.g., Fc304) and complexes of iron. Mixed valence trinuclear /.t-oxo-carboxylato-complexes are dealt with in Section 5.4.5.4.2, polynuclear complexes held together by sulfide bridges in Section 5.4.5.9.2. 

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