Oxo-alkoxides heterometallic

Both homometallic and heterometallic oxo-alkoxides can be produced by partial hydrolysis of metal alkoxide precursors via dehydroxylation and dealkoxolation of metal hydroxo alkoxides. The crystal structures of a number of polynuclear titanium oxo alkoxides have been elucidated, these structures having evolved during the slow addition of small amounts of water to Ti(OEt)4 47,48,76-79... 

Heterometallic oxo-alkoxides may also be formed by conversion from heterometallic alkoxides. Thus the insoluble [Pb(OPr)2]j reacted with Ti(OPr% to form [Pb4Ti403PPr g] and [Pb2Ti2(Ai4-0)(/u,3-0Pr )2(/Li-0Pr )4(0Pr )4] presumably by ether elimination. Similarly, from reactions of barium alkoxides and titanium alkoxides the heterometallic oxo-alkoxides [Ba4Ti404(OPr )i6(Pr OH)4][Ba4Ti404(OPr )io(Pr OH)3] and [Ba2Ti40(0Me)ig(Me0H)7]2° were obtained as a result of ether elimination, although similar complexes are readily prepared when the barium alkoxide solution is aerobically oxidized. ... 

Ester elimination has been employed successfully in the synthesis of heterometallic oxo-alkoxides (Eq. 5.15). ... 

The centrosymmetrical heterometallic oxo-alkoxide-diketonate molecule [Ba2Y4(/i6-0)(/Li3-0Et)g(Bu C0CHC0Bu )6] also contains an octahedrally encapsulated /Lts-oxo-ligand. ... 

A vanadium(v)-molybdenum(vi) heterometallic oxo-alkoxide [V2Mo2(0)g (0Me)2 (0CH2)3C(CH20H) 2] has also been characterized. The V2M02O16 core involving octahedral metals is reminiscent of the Ti40ie core of titanium tetraUcoxides. ... 

Oxo-alkoxides are partially condensed species and represent a new class of sol-gel precursors. These species are oligomeric and can be either homometallic or heterometallic. In many cases the oxo bridges produced in these compounds are multiply bridging, in order to achieve the most favored coordination number of six for metal atoms in alkoxide species. Isolation of compounds with similar multiply bridging oxygen atoms has been observed by the reaction of metals with the appropriate phenol or alcohol, with, in some cases, reaction with solvent molecules producing compounds quite different from the simple binary alkoxides expected.72 Besides isolation of intermediates, it is also possible to monitor the reactions by NMR and mass spectrometry 73... 

Oxo)alkoxide clusters Various homogeneous and heterometallic Precursors to metal oxide materials Flubert-Pfalzgraf (2003)... 

Alkali-metal Containing Oxo-alkoxides (Including Heterometallic Compounds)... 

Table 5.3 Scandium, yttrium, lanthanide, and actinide-containing oxo-alkoxides (including heterometallic compounds)...

Oxo-alkoxides of Nickel, Copper, Aluminium, Tin, and Lead (Including Heterometallic Compounds) (Table 5.9)... 

Although no oxo-alkoxide structures involving cobalt or nickel appear to have been reported there is an interesting octanuclear nickel antimony heterometallic compound [Ni5Sb3(/u.4-0)2(/u,3-OEt)3(/r-OEt)9(OEt)3(EtOH)4] in which the Ni(n) atoms are octa-hedraUy coordinated, one Sb is four-coordinated (lone pair in the vacant site of a... 

Most ceramics and glasses are based on silica. The problem then is to form Si-O-M bonds in the molecular precursor and to keep them during the whole hydrolysis and condensation processes. However, silicon has a rather high electronegativity (XSi=L74) and does not show any tendency toward coordination expansion. Its chemical reactivity toward hydrolysis and condensation is therefore quite low. Silicon alkoxides Si(OR)4 always exhibit a monomeric tetrahedral molecular structure and very few heterometallic alkoxides or oxo-alkoxides are formed with silicon (4). It is therefore difficult to prepare homogeneous multicomponent gels in silicate systems... 

Heterometallic Oxoalkoxides. Condensation between two alkoxide molecules can also proceed via ether elimination leading to the formation of fx-oxo bridges (5). 

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