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Thorium alkoxides

The first studies of thorium alkoxides were carried out by Bradley [223] in the mid-950s in connection with the problem of the separation of rare elements of Group IV and Ce(IV). They were devoted at the same time to the solution of certain theoretical problems such as the influence of the size of the central [Pg.367]

Chemical composition. Structure Synth. route Properties Investig. methods Ref. [Pg.369]

The majority of Th(OR)4 have been isolated in the crystalline form only as pyridine solvates and Th(OBu )4 — as alcohol solvate (with 2 1 composition), the yields of complexes being rather far from quantitative [387]. This fact in combination with the observed molecular complexities (3-4) for unsolvated Th(OR)4 (R = Pf, Bu, C5H , C5H , CjH, ) — amorphous solids or viscous liquids—permits to suppose (in analogy with Zr(OR)4 and Hf(OR)4 , see Section 12.12) the existence in their samples oftri- and tetranuclear oxocom-plexes — MjO(OR)10 and M40(0R),4 — to be supposed. Crystalline Th3O(OBu )i0 has in fact been isolated on the hydrolysis of [Th(OBul)4Py2] [387] (Table 12.14). [Pg.372]

One of the possible applications of Th(OR)4 has been proposed by Mazdi-yasni [1082], who reported the preparation of fine Th02 powder on the oxidative pyrolysis of alkoxides in the gas phase. [Pg.372]


The X-ray crystal structure of homoleptic thorium alkoxide [Th(OCH-t-Pr2)4]2 (299) is shown in Fig. 44. Each thorium atom adopts a distorted trigonal bipyramidal geometry, and the Th208 core can be viewed as two trigonal bipyramids fused along a common axial-equatorial edge. [Pg.337]

On the basis of the kinetic and thermodynamic data, a plausible mechanism for the Tishchenko reaction is presented in Scheme 15. In the first step of the reaction, the precatalyst 1 reacts with two equivalents of the aldehyde to give exothermically the alkoxo complex 42 (Step i in Scheme 15 AHcaic = —68 kcal/mol). A second insertion of an aldehyde into the thorium-alkoxide bond yields complex 43 (step ii in Scheme 15). The concomitant hydride transfer from complex 43 to an additional aldehyde releases the ester 44 and produces the active catalytic species 45 (step iii in Scheme 15). The insertion of an aldehyde into complex 45 (step iv, AHcaic = —25 kcal/mol) gives complex 46, and its hydride transfer reaction (step v, rate determining step, AHcaic = —22 kcal/mol) with an additional aldehyde via a plausible six-centered chair-like transition state (47) produces the ester 38 and regenerates the active complex 45. [Pg.179]

Table 2.11 Volatilities and molecular complexities of cerium and thorium alkoxides... Table 2.11 Volatilities and molecular complexities of cerium and thorium alkoxides...
Oxygen-Gontaining Organics. Neutral and anionic oxygen-containing organic molecules form complexes with thorium. Recent work has focused on alkoxides (72), aryloxides, and carboxylates however, complexes with alcohols, ethers, esters, ketones, aldehydes, ketoenolates, and carbamates are also well known. [Pg.39]

If hydrogen gas is added to the reaction mixture of J, and 11 the hydrogenolysis reaction of thorium-to-carbon sigma bonds (J-1 22) allows interception of species 13 and thus, catalytic hydrogenation of the inserted carbon monoxide functionality. At 35 C under 0.75 atm initial H2 pressure with [JJ =9.0 x 10" M and [ 1JJ = 6.5 x 10" M, hydrogenation and isomerization are competitive and both the enolate and the alkoxide reduction product 14 are produced (eq.(13)). Under these conditions, turnover fre-... [Pg.72]

Alkoxide gels, 23 60 Alkoxide gels, in optical fiber manufacturing, 11 145 Alkoxide initiators, 14 259 Alkoxide ligands, thorium, 24 770 Alkoxides, 12 190 25 72-86 controlled hydrolysis of, 23 56 iron, 14 533 mixed-metal, 25 100 titanium, 25 82 uranium complexation with,... [Pg.31]

Metathetic exchange of alkoxide or phenoxide for halide is possible using either lithium or sodium salts. For instance, thorium tetraalkoxides55 are best obtained from the reaction shown in equation (8). [Pg.338]

Mixed hydrido-alkoxides and -phenoxides of thorium have been synthesized by the reaction shown (equation 31).104... [Pg.341]

The alkoxides of actinides are rarely studied except the derivatives of uranium and thorium, as interest in the alkoxides of these 2 elements has increased by the hope to use them in the isotope-separation processes. The study of uranium alkoxides was initiated by groups led by Gilman and Bradley in the 1950s. The major part of this work is still carried out at the Nuclear Research Center at Los Alamos in the United States by the group of Sattelberger et al. [1671]. The detailed data on alkoxides ofuranium is provided in a number of... [Pg.434]

Figure 8 Phospha-alkoxide complex generated by insertion of carbon monoxide into a homoleptic thorium dialkylphosphide complex (Edwards, Hursthouse et al. J. Chem. Soc., Chem. Commun. 1994, 1249). Figure 8 Phospha-alkoxide complex generated by insertion of carbon monoxide into a homoleptic thorium dialkylphosphide complex (Edwards, Hursthouse et al. J. Chem. Soc., Chem. Commun. 1994, 1249).
Carbonyl insertion into the metal-hydrogen bond of an organometallic thorium(IV) compound is successful when there are bulky substituents on the alkoxide group ... [Pg.640]

Both thorium(IV) alkoxides react rapidly and reversibly to give formyl complexes with the following thermodynamic parameters R = CH-t-Bu2, AH° = — 18.8 + 3.8 kJ/mol,... [Pg.642]

While the chlorides of strongly electropositive elements such as thorium, lanthanides, and some later 3d metals form adducts with alcohols (57), anhydrous chlorides of boron (6) and silicon (9) form the corresponding alkoxides or alkyl orthoesters, B(OR)3 and Si(OR)4, with primary and secondary alcohols. The reactions of tertiary alcohols are complicated by the facile side formation of tertiary alkyl chloride and water by the reaction between tertiary alcohols... [Pg.248]

The electronic structure of the alkoxide complexes Cp3U(OR) and Cp3Th(OR) has been investigated by He(i) and He(n) UV photoelectron spectroscopy combined with SGF Xa-DVM calculations. Full relativistic Dirac-Slater calculations were also carried out for the thorium complexes.67 Comparative relativistic effective core potential ab initio calculations have been reported for both Th(iv) and U(iv) Cp3AnL (L = Me, BH4) complexes.68... [Pg.204]

For the synthesis of metalloid (B, Si) alkoxides, the method generally employed consists of the reaction of their covalent halides (usually chlorides) with an appropriate alcohol. However, the replacement of chloride by the alkoxo group(s) does not appear to proceed to completion, when the central element is comparatively more electropositive. In such cases (e.g. titanium, niobium, iron, lanthanides, thorium) excluding the strongly electropositive s-block metals, the replacement of halide could in general be pushed... [Pg.4]


See other pages where Thorium alkoxides is mentioned: [Pg.40]    [Pg.947]    [Pg.367]    [Pg.368]    [Pg.369]    [Pg.40]    [Pg.27]    [Pg.197]    [Pg.65]    [Pg.267]    [Pg.40]    [Pg.947]    [Pg.367]    [Pg.368]    [Pg.369]    [Pg.40]    [Pg.27]    [Pg.197]    [Pg.65]    [Pg.267]    [Pg.224]    [Pg.38]    [Pg.59]    [Pg.34]    [Pg.435]    [Pg.38]    [Pg.224]    [Pg.147]    [Pg.208]    [Pg.212]    [Pg.221]    [Pg.223]    [Pg.639]    [Pg.263]    [Pg.224]    [Pg.300]    [Pg.316]   
See also in sourсe #XX -- [ Pg.32 , Pg.55 , Pg.65 , Pg.82 , Pg.83 , Pg.266 , Pg.267 ]




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