Cobalt methoxide

Nickel and cobalt methoxides, M(OMe)2 (M = Ni, Co), are reported to be unreactive towards carbon dioxide. However, it has been demonstrated that Cu(OMe)2 in the presence of pyridine reacts with two moles of CO2 to yield the corresponding carbonate (Eq. 2.287) 34... 

The reaction conditions were mild (room temperature, 1 atm CO) and a two-fold excess of base was used along with a catalytic amount of cobalt carbonyl. The product distribution was quantified by VPC. The mixtures contained starting material, ester product, and various amounts of methyl benzyl ether. No detectable amounts of benzyl alcohol, ketones, or hydrocarbons were seen. Potassium methoxide alone afforded mostly the ether. A mixture of potassium methoxide and alumina gave a slight improvement in ester yield but the predominant product was again the ether. In contrast, when potassium methoxide on alumina was used, the carboxyalkylated product, methyl phenylacetate, was prepared in 70 yield with little ether detected. Benzyl chloride reacted in a similar fashion under these mild reaction conditions. Other alkoxide and carbonate bases could be used as... 

Before addition of the benzyl halide, the only carbonyl adsorption peak is found at 1900 cm, indicative of the cobalt tetracarbonyl anion. After addition, this band immediately disappears and peaks at 2000 cm l are observed. These most likely represent the corresponding acyl complex. Reaction with methoxide yields the product and regenerates the cobalt anion. In the absence of sufficient methoxide, the reaction requires attack by the much... 

The results from our work on the reaction of propylene oxide with cobalt carbonyl and base in methanol are given in Table VIII. Several base/metal oxide combinations were evaluated under mild reaction conditions. The difference in activity between the bases was not as pronounced as that observed in the reaction with benzyl halides with the exception of potassium methoxide which, when used alone, gave exclusively the hydroxy ether resulting from methoxide addition to the epoxide ring. However, the activity of sodium... 

The first attempts to prepare cobalt and nickel ethoxides were reported in 1936 by Meerwein [1102] and Kandelaki [875]. Application ofNaOR in the exchange reactions could not, however lead to the obtaining of the pure products of purpose as they were insoluble in the parent alcohol. Application of LiOR for this purpose permitted Adams et al. in 1966 to obtain the individual M(OMe)2 — derivatives of id-transition elements in the series from Cr to Cu [6]. In the 1980s Mehrotra et al. have described the homologous series of Ni(OR)2 — from methoxide to r-hexyloxide [99], and also Co(OR)2, where R = Me,Et, Pr [1108]. On the alkoxylation of CoH(N2)(PPh3)3 by esters, phenol, or fluorinated ketones, Hayashi et al. [720] have obtained a series of tetrahedral [Co (OR)(PPh3)3] complexes. 

A special role in the chemistry of nickel and cobalt alkoxide derivatives is played by the poorly soluble methoxide halids studied in detail by the group of Winter [964, 865]. According to the diffuse reflectance spectra, the coordina-... 

The lack of reactivity at C-3 of the a-D anomer as compared with that of the /8-D anomer of methyl 4,6-O-benzylidene-D-glucoside has been noted by other workers. Presumably, the bulky cobalt tetra-carbonyl anion is hindered from approaching C-3 by the methoxyl group on C-1, whereas the less bulky methoxide ion, or hydroxide ion, can open the epoxide ring in the normal, frans-diaxial way. 

As indicated in Section 11,4 (p. 64), direct treatment of alkyl halides with sodium cobalt tetracarbonyl, carbon monoxide, and methanol at elevated temperatures and pressures yields esters. Surprisingly, application of this reaction at 60° (using methanol instead of ether) to methyl tri-0-acetyl-2-deoxy-2-iodo-/3-D-glucopyranoside gave, almost exclusively, the elimination product (88) (in deacetylated form) and a compound presumed to be (on the basis of nuclear magnetic resonance evidence only) the branched-chain ester (87) in less than 0.5 % yield. It is thought that, in the presence of methanol, the sodium cobalt tetracarbonyl dissociates to yield sodium methoxide, and that this causes deacetylation of the substrate. 

The order of reactivity, MNR2 > MOR, is illustrated by the reaction of (Et2N)Ti(OPr-i)3 with CO2 to give the carbamate (Et2NC02)Ti(0Pr-i)3 . Solvent may break up the polymeric structure of the metal oxide or alkoxide, or associate with the metal. Thus copper(II) methoxide [but not cobalt(II) or nickel(II) methoxide] absorbs CO2, at RT in pyridine, but not in tetrahydrofuran (THF), dimethylformamide (DMF), triethylamine, or tetramethylethylenediamine . ... 

A plausible mechanism for the reaction includes several organometallic species that are sensitive to reactive moieties elsewhere in the molecule. If a chloro, chloromethyl, or mesyloxymethyl substituent is attached vicinal to the 1,1 -dibromo moiety, efficient ring opening occurs prior to carbonylation and P,y- and y, -unsaturated acid derivatives are formed. Reductive carbonylation has also been achieved with 1,1-dibromocyclopropanes using an excess of pentacarbonyliron in dimethylformamide with added methanol or sodium methoxide, or cobalt(II) chloride and nickel(ll) cyanide under phase-transfer conditions in a carbon monoxide atmosphere. However, the yield of cyclopropanecarboxylic acid derivatives is low, and when pentacarbonyliron is used the amount of monobromides is fairly high. ... 

Acylcobalt carbonyl derivatives are cleaved by sodium methoxide to esters and sodium salts of the corresponding carbonyl anions. By means of this reaction, acetyl[bis(trimethylolpropane phosphite)]cobalt dicarbonyl has been converted into sodium [bis(trimethylolpropane phosphite)]cobalt dicarbonyl. The latter compound is readily alkylated by methyl iodide to form the methylcobalt derivative and this compound in turn reacts with another mole of the phosphite ester, in the same way that methylcobalt tetracarbonyl does, to form acetyl[tris(trimethylolpropane phosphite)]-cobalt carbonyl ... 

This sequence of reactions may be carried further by cleaving the last product with sodium methoxide and alkylating again with methyl iodide to produce methyl[tris(trimethylolpropane phosphite)]cobalt ... 

The diffuse reflectance spectrum of cobalt iodide methoxide was rather complex and showed a large charge transfer band in the visible region. However, some discontinuity was observed around 16000 and 18000cm" which was assigned to a 4Ti(P) charge transfer edge. 

The cobalt(n) methoxide shows variation of magnetic moment with temperature involving an octahedral CoOe model (jU-eff = 5.46B.M.,0 = 15°) The halide methox-ides also follow the Curie-Weiss law and thus chloride methoxide exhibits a room temperature magnetic moment of 4.89 0.01 The expected spin only magnetic... 

Z)-Alk-2-enenitriles are also available from the hydrocyanation of acetylenes, which occurs with cis stereospecificity when catalysed by a nickel(O) complex, and from the stereoselective cyanation of vinyl halides, catalysed by tetracyano-cobaltate(i). The latter procedure is equally applicable to the stereoselective synthesis of the corresponding ( )-isomers. Also, the ( )- and (Z)-isomers (17) and (18) react with piperidine with retention of configuration to provide (19) and (20) respectively (Scheme 30). In contrast, the corresponding reaction with sodium methoxide gives rise to the (Z)-isomer only. 

Fluorination of cycloheptane or cycloheptatriene with cobalt trifluoride leads to dodecafluorocycloheptanes, which may be converted into decafluoro-cyclohepta-1,3- and -1,4-dienes and into octafluorocyclohepta-l,3,5-triene. ° The latter is extremely easily hydrolysed to hexafluorotropone, which gives a tetrafluorodimethoxytropone on reaction with sodium methoxide. 

The equilibrium constant K for the substitution of coordinated H2O in the cobalt(III) corrinoid aquacyanocobamide (vitamin B12) by various amines and six-membered heterocycles in aqueous solution was determined by the same authors the results have special relevance to the mentioned work. " In the quoted paper, the CN" ligand is firmly held and can be considered inert (at least in the dark), while the H2O ligand is kinetically very labile in addition, the reaction took place in aqueous solution and is of dissociative nature type " ). Analogously, in the (MeOH) and (MeO) replacements " methoxide... 

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