Zirconium methoxide

Zirconium alkoxides behave similarly in regard to thermal stability. The series zirconium methoxide [28469-78-5] zirconium ethoxide [18267-08-8] zirconium isopropoxide [2171 -98 ] zirconium /r /f-butoxide [2081 -12-1] shows decreasing thermal stability. 

No formation of bimetallic complexes is observed on MoO(OPr )4 dissolution in the alcohol solutions of zirconium isopropoxide, due presumably to the high stability of the structure of the latter. A very unusual complex of Zr3Mo,024(OPri)12( PrOH)4 composition precipitates slowly from solutions of isopropoxides in hexane subjected in advance to evacuation to dryness and redissolution repeated three times. The structure of the complex obtained is very close to that of the zirconium methoxide hydrolysis product, Zr O OMe) (Fig. 5.1 c) [901]. The formation of a complex very rich in oxoligands is presumably due to the trend of ZrCOPhV PrOH to form oxocomplexes on desolvation (see Section 12.12). 

In none of the cases discussed above is molecular hydrogen involved. The first report of the stoichiometric reduction of coordinated carbon monoxide by molecular hydrogen is that published by Bercaw et al. (35, 36). They reported that mononuclear carbonyl and hydride complexes of bis(pentamethylcyclopentadienyl)zirconium are capable of promoting stoichiometric H2 reduction of CO to methoxide under mild conditions. Thus, treatment of the dicarbonyl complex (rj5-C5Me5)2Zr(CO)2 with... 

The fate of 10 depends on whether or not the zirconium dihydrido species, (T75-C5Me5)2ZrH2, is present. In the presence of the dihydride, further reduction occurs to yield the methoxide complex (7). In the absence of the dihydride, 10 undergoes a dimerization reaction, yielding 11 ... 

Of interest is the fact that the H2 required for the reduction of formyl to methoxide in reaction (73) is thought (428, 429) to come from a second zirconium moiety, ZrH2. The H2 reduction to coordinated hydroxymethyl in Eq. (72) could presumably go via a mononuclear H2M(CHO) intermediate, but such a reaction has not been demonstrated, nor has the final hydrogenolysis step via a presumed H2M(CH2OH) intermediate. Loss of water from this to give a carbene HM=CH2 (431, 432) followed by further reactions with H2 and CO, provides speculative pathways to higher hydrocarbons (417, 419a, 430, 433). 

Figure 3 The arrangement of zirconium atoms (solid circles) and oxygen atoms (open circles) in molecules of [Zr13Og(OMe)36] 0(2) and 0(3) are bridging oxygen atoms while the other oxygen atoms are part of methoxide...

The direct electrochemical synthesis of metal alkoxides by the anodic dissolution of metals into alcohols containing conducting electrolytes was initially demonstrated by Szilard in 1906 for the methoxides of copper and lead.19 More recently the method has received some attention particularly in the patent literature.29-25 The preparation of the ethoxides of silicon, titanium, germanium, zirconium and tantalum by electrolysis of ethanolic solutions of NH Cl has been patented, although the production of the ethoxides was found to cease after several hours.24,25... 

Sol-gel processing techniques have largely been applied to main group alkoxides, particularly Si and Al, but increasingly studies have dealt with early transition metal elements such as Ti and Zr. The preparation of metal alkoxides has been reviewed extensively.46 18 Self-condensation of alkoxides can occur, depending on the steric demands of the alkoxide group for example, Ti methoxide, ethoxide, and isopropoxide are tetrameric, trimeric, and dimeric, respectively,49 while the zirconium isopropoxide is tetrameric.50... 

Another example of the nucleophilic chloro ligand substitution involves the reaction of the zirconium dichloride complex 468 with lithium ester enolates (Scheme 112). Its reaction with 2 equiv. of stable lithium ester enolates such as lithium tert-butyl isobutyrate in TF1F produces the bis(ester enolate) complex 499 as a crystalline solid.344 The same reaction but with the unstable lithium methyl isobutyrate leads to the isolation of the decomposition product, the bis(methoxide) complex 500, which exists as a dimer in the solid state. Treatment of the bis(ester enolate)... 

C3gHygCrO, Tetrakis[bis(t-butyl)methoxo]chromium(IV), 46B, 1161 C36Hio80ftuZr13, Zirconium oxide methoxide, 43B, 1379 C38H3gAs2Cl2Co03, Bis(triphenylarsine oxide)dichlorocobalt(II) -ethanol, 43B, 1380... 

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