Fluorinated diketone complexes

The efficient and selective catalysis of some Diels-Alder reactions by lanthanide P-diketonate complexes has been known since 1975 [226, 227]. The fluorinated p-diketonate complexes Ln(fod)3 (cf. Scheme 12.5) selectively catalyze the Danishefsky transformation (Scheme 12.23) as a consequence of their mild Lewis acidity. Importantly, zeolites and Lewis acid modified silica or alumina also catalyze Diels-Alder reactions [228-232]. 

Many [M(dik)4] complexes are volatile, especially those that contain fluorinated diketonate ligands. Mass spectra and gas chromatographic behavior of several of these complexes have been studied (see Table 10). Isenhour and coworkers240 241 have employed fluorinated diketonates in mass spectrometric procedures for determination of Zr and Zr/Hf ratios in geological samples. The most intense peak in mass spectra of [M(dik)4] complexes is [M(dik)3]+. Sievers et al.242 have used gas chromatography of metal trifluoroacetylacetonates to separate Zr from Al, Cr and Rh. However, attempts to separate [Zr(tfacac)4] and [Hf(tfacac)4] by gas chromatography were unsuccessful. Zirconium and hafnium can be separated by solvent extraction procedures that employ fluorinated diketones.105 [M(dik)4] (M = Zr or Hf dik = acac, dpm, tfacac or hfacac) have been used as volatile source materials for chemical vapor deposition of thin films of the metal oxides.243,244... 

Complexes of platinum(II) with /J-monothiodiketonates, derived by deprotonation of the parent acid (207), can be prepared from PtCl -. The dark red complex Pt(C3H(Ph)2SO 2 (R = R = Ph) shows IR bands at 1535 cm-1 [v(C=C)], 1410 cm-1 [v(O O)] and 1270 cm-1 [v(O S)].1824 Electronic spectra and dipole moment data for these complexes have been compared with the O.O -diketonate complexes.182s 1826 The structure of the phenyl derivative has been confirmed by X-ray crystallography.1827 Detailed dipole moment measurements using static polarization have been made with fluorinated jS-monothiodiketone complexes. Variations with substituent depend on the magnitude and vector directions of the Ph—X bond moments (aryl substituents), the inductive effect of the meta and para substituent on the phenyl ring, and the mesomeric effect of the substituent X.1828 A useful separation method for bis(monothiotrifluoroacetylacetonates) of platinum(II) is gas chromatography.1829... 

Judging by their appearance, monoclinching alcohols resemble j8-diketonate ligands (Fig. 13). Bulky (tBu) or fluorinated (CF3) alkyl groups in R1 and R3 position ensure volatility of /J-diketonate complexes [107]. 

Triarylantimony(V) bromides react with fluorinated /9-diketones in the presence of triethylamine to yield the oxygen bridged enol type /3-diketone complex (Ar3SbL)20, which when heated in moist organic solvent yields hydrated /8-diketone complexes of... 

Recent work by Cole-Hamilton and coworkers has demonstrated that stability and volatility are enhanced by the use of long-chain fluorinated p-diketonate ligands, that is those derived from Hdfhd (6) and Htdfhd (7). The hydrafed bis(/3-diketonate) complexes M(dfhd)2(H20) and M(tdftid)2(H20) were prepared for Cu, Ca, Sr, and Ba and were all found to sublime below 200 °C with weight loss ranging from 85 to 98% (see Table 15). In addition, the anhydrous compound Ba(tdfiid)2 was reported to melt at 196 °C and volatilize at 220 °C with essentially no decomposition (residual mass by TGA ca. 1%). 

Beryllium chemistry includes its S-diketonate complexes formed from dimedone (9), acetylacetone and some other S-diketones such as a,a,a-trifluoroacetylacetone. However, unlike the monomeric chelate products from acetylacetone and its fluorinated derivative, the enolate species of dimedone (9) cannot form chelates and as the complex is polymeric, it cannot be distilled and is more labile to hydrolysis, as might be expected for an unstabilized alkoxide. However, dimedone has a gas phase deprotonation enthalpy of 1418 9 kJmoD while acetylacetone enol (the more stable tautomer) is somewhat less acidic with a deprotonation enthalpy of 1438 10 klmoD Accordingly, had beryllium acetylacetonate not been a chelate, this species would have been more, not less, susceptible to hydrolysis. There is a formal similarity (roughly 7r-isoelectronic structures) between cyclic S-diketonates and complexes of dimedone with benzene and poly acetylene (10). The difference between the enthalpies of formation of these hydrocarbons is ca... 

Incorporating fluorocarbon moieties increases the volatility of / -diketonate complexes 18). To retain the steric effect of the bulky thd ligands and to take advantage of the volatility effect of fluorocarbon substituents, the ligand, l,l,l,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octane-dione, [H(fod)] ( see Figure 5 for structure of anion), was synthesized. Fifteen tris complexes of tervalent rare earth metal ions with this bulky fluorinated ligand have been prepared and studied. Their properties are compared with other rare earth complexes, principally those of thd. 

The complex formed by extraction of uranium(IV) from an acidic aqueous solution by benzoyltrifluoroacetone in carbon tetrachloride is also reported to be a useful shift reagent, the shifts induced being to lower frequency. (4) Adducts with complexes formed from uranium(IV) and other fluorinated diketones are also mentioned, but no details of shifts are given. 

Hence, synthetic organolanthanide chemistry puts the main emphasis on the adaption of prevailing precatalyst types to the requirements of highly enantiose-lective catalysis. This is impressively demonstrated by tied-back cyclopentadienyl complexes [207], even water-stable BINOL systems [43], and fluorinated (3-diketonate complexes (Fig. 11) [208]. 

Furthermore, a homogeneous composition is observed throughout the film bulk region by AES depth profiling. This establishes the suitability of fluorinated "second generation y3-diketonate complexes as precursors forTBCCO films by CVD. 

Gas chromatographic studies of ethers, ketones, alcohols, esters, olefins, and alkanes, using columns with liquid phases containing P-diketonate complexes in squalane, revealed that the more nucleophilic organic substrates reacted more strongly with the P-diketonates than the less basic ones. Er complexes of fluorinated P-diketones (especially 3-trifluoroacetyl-d-camphor-ate, facam) reacted more strongly with these nucleophiles than did similar non-fluorinated Er complexes. The retention time of THE increased exponentially with the inverse of metal ionic radius in the facam chelates of a variety... 

Although this makes the quantitative extraction of the rare earths possible in a single extraction it does not necessarily improve the selectivity of the extraction method because many other elements are also quantitatively extracted. Sieck (197 L) reported that the rare earths were quantitatively extracted in a single stage operation by various fluorinated -diketones and dibutylsulfoxide (the neutral donor). These ternary complexes were sufficiently volatile that several individual rare earths could be separated by gas-liquid chromatography. 

Martin-Ramos P, Silva MR, Coya C, Zaldo C, Alvarez AL, Alvarez-Garcia S, Matos Beja AM, Martin-Gil J (2013) Novel erbium(iii) fluorinated [small beta]-diketonate complexes with N, N-donors for optoelectronics from synthesis to solution-processed devices. J Mater Chem C 1 (15) 2725-2734... 

Hydrolysis of 3. Unlike 1, which required pyridine to promote hydrolysis, complex 3 was hydrolyzed upon exposure to ambient moisture, both in the solid state and in solution. No added base was required. The electron-withdrawing nature of the hexafluoroacetylacetonate ligands makes the titanium center a stronger Lewis acid and therefore more susceptible to hydrolysis. The course of the hydrolysis of 3 is superficially similar to that of 1, but several major differences are observed that arise from the fluorinated diketonate ligands. 

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