Ethoxide complexes

Dimethyl sulfoxide (DMSO) prevents precipitation of intermediate salts, which can also be achieved by using a larger volume of dimethylformamide (DMF) (ca. 200 ml.). Attempts to prepare the diethyl oxalate/potassium ethoxide complex in DMSO have not been successful (i.e., it is not active). ... 

The reaction can be monitored by TLC (CHgCl2). The spots were developed with an ethanolic solution of p-dimethylaminobenzaldehyde/HCl. The product gave a bright red spot at Rf 0.5 and the imidate ester gave a yellow spot at Rf 0.6. Addition of small portions of diethyl oxalate/potassium ethoxide complex was continued if the starting material was not consumed after the initial reaction period. 

The diethyl oxalate/potassium ethoxide complex can also be prepared by adding the oxalic ester to an ethanollc solution of potassium ethoxide and evaporating the solvent. However, this complex is less active and is difficult to store. 

Related monometallic, dimetaUic, and cationic Zn complexes supported by tridentate bis(pyrazolyl)amine ligands have been reported for the polymerization of rac-LA and methyl methacrylate (Figure 8). " All three complexes are active for the polymerization of rac-LA, reaching conversions of >90% in 30h (unoptimized time) at room temperature. Whereas the ethoxide complex is slightly more active and better controlled than the ethyl and cationic complexes, it produces atactic PLA. 

All the ethoxide complexes isolated in this series are dinuclear in the solid state. " " Their solution stractures were determined by pulsed gradient spin-echo (PGSE) NMR... 

Deprotonation of the racemic or enantiopure salen proligand featuring a trans cyclohexyldiamine backbone (ONNO) and subsequent salt metathesis with indium trichloride and sodium ethoxide in a three-step process involving an indium chloride intermediate yields racemic or enantiopure indium ethoxide complex [(ONNO) In(p-OEt)j2 (2) (Figure 34). 2" ... 

Deprotonation of the zinc alcohol complexes shown in Fig. 12 to produce zinc alkoxide species has not been reported. Instead, mononuclear, tetrahedral zinc alkoxide complexes, supported by hydrotris(pyrazolyl)borate ligands, ([TpBut,Me or Tpph,Me, Scheme 8), have been generated via treatment of zinc hydride precursor complexes with aliphatic alcohols.68-70 A zinc ethoxide complex, [TpBut,Me]Zn-OEt, was also prepared via decarboxylation of the ethyl carbonate complex, [TpBut,Me]Zn-0C(0)0Et.49 X-ray crystallographic studies of [Tpph Me] Zn-OCH3 and [TpBut,Me]Zn-OEt revealed Zn-O bond lengths of 1.874(2) and 1.826(2) A, respectively.68,71 These bond distances are 0.1 A shorter than found for the alcohol complexes shown in Fig. 12. 

In a model reaction for liver alcohol dehydrogenase, the zinc ethoxide complex [TpBut,Me]Zn-OEt reacts stoichiometrically with -nitrobenzaldehyde in benzene to produce [TpBut,Me]Zn-0CH2C6H4N02 and acetaldehyde (Scheme 10).68 For a series of similar reactions involving the zinc isopropoxide complex [Tpph,Me]Zn-OCH(CH3)2 and various aromatic aldehydes in toluene (Scheme 10), the zinc-containing products of the reaction, [Tpph,Me]Zn-OCH2Ar, were isolated in 60-70% yield, while the acetone produced was identified using ]H NMR.70... 

In P-CH elimination on d -metal ethoxide complexes, the orbital interactions have to take place in such a manner that the electron donation from cr(CH) to o (MO) and the back-donation from sigma (M) to ct (CH) are required to form the MH o and CO n bonds and... 

The C-0 bond cleavage of dialkyl ethers is much more difficult than that of alkyl aryl ethers. Nevertheless some lanthanoid complexes are known to cleave C-0 bond of diethyl ether (Eq. 3.20) or dimethoxyethane (Eq. 3.21) to give ethoxide complexes [82,83]. 

Bergquist. C. Perkin. G. Modeling the eatalytic cycle of liver alcohol dehdrogenase Synthesis and structural characterixation of a four-coordinate zine ethoxide complex and determination of relative Zn—OR versus Zn—OH bond enegiees. Inorg. Chem. Acta 1999, 38 (3). 423-442. 

Among the various allylic compounds, allylic carbonates are most reactive toward Pd(0) species. The reaction of an allylic carbonate with Pd(0) initially provides a 7r-allyl-palladium carbonate complex, which immediately loses carbon dioxide to form a tt-allylpalladium ethoxide complex irreversibly. Thus, their carbonylation proceeds under mild conditions, namely, at 50 °C under 1-20 atm of carbon monoxide (Scheme... 

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