Beryllium alkoxides

In addition to the oxide carboxylates, beryllium forms numerous chelating and bridged complexes with ligands such as the oxalate ion C204 , alkoxides, /9-diketonates and 1,3-diketonates. These almost invariably feature 4-coordinate Be... 

Reaction of beryllium dialkyls with an excess of alcohol yields the alkoxides Be OR)2. The methoxide and ethoxide are insoluble and... 

Metallotropic rearrangement, in mercury tri-azenide complexes, 30 41 Metals, see also Heterobimetallics specific element Transition metal complex alkoxides, 15 159-297 of actinides, 15 290-293 of alkali metals, 15 260-263 of alkaline earths, 15 264-266 of aluminium, 15 266-272 of beryllium, 15 264-266 double type, 15 293-294 of gallium, 15 266-272 of lanthanides, 15 290-293 of magnesium, 15 264-266 properties of, 15 260 of transition metals, 15 272-290 trialkylsilyloxides, 15 295-297 of zinc, 15 264-266... 

Te tram eric alkyl beryllium, zinc and cadmium alkoxides are formed by controlled alcoholysis of the metal dialkyls,16U62 while cubanoid thallium alkoxides are obtained by reaction of the metal with refluxing ethanol, and alcohol metathesis.163 Reaction (4) affords a tin phosphide cubane in low yield 164... 

In all of, these cases substitution of the second alkyl can then occur to yield the dialkoxide or diphenoxide. This allowed the isolation of the monomeric beryllium phenoxide Be(OAr )2 (OAr = 2,6-di-t-butylphenoxide).98 The alkyls of the Group IV metals, MR (M = Ti, Zr, Hf), undergo rapid reactions with common alcohols and phenols yielding eventually the corresponding tetra-alkoxides or -phenoxides and four equivalents of alkane.97,100 With very bulky substituted alcohols or phenols the reactivity can be very sluggish, in some cases leading to only partial substitution (equation 28). 66,100... 

Other important beryllium oxygen complexes are the alkoxides, a typical example being the tert-butoxide (4-1) other, 3-coordinate alkoxides, e.g., Be 0(2,4,6-Bu3C6H2) 2(OEt2), are known and readily made by interaction of LiOR and Bed2(OEt2)2.4 The tetrahedral structure of the latter was also confirmed, being similar to that in other solvates. 

Beryllium chemistry includes its S-diketonate complexes formed from dimedone (9), acetylacetone and some other S-diketones such as a,a,a-trifluoroacetylacetone. However, unlike the monomeric chelate products from acetylacetone and its fluorinated derivative, the enolate species of dimedone (9) cannot form chelates and as the complex is polymeric, it cannot be distilled and is more labile to hydrolysis, as might be expected for an unstabilized alkoxide. However, dimedone has a gas phase deprotonation enthalpy of 1418 9 kJmoD while acetylacetone enol (the more stable tautomer) is somewhat less acidic with a deprotonation enthalpy of 1438 10 klmoD Accordingly, had beryllium acetylacetonate not been a chelate, this species would have been more, not less, susceptible to hydrolysis. There is a formal similarity (roughly 7r-isoelectronic structures) between cyclic S-diketonates and complexes of dimedone with benzene and poly acetylene (10). The difference between the enthalpies of formation of these hydrocarbons is ca... 

Beryllium is an understandable exception, but then its salts are more covalentHowever, by the use of less stable salts such as alkoxides, R3AI can produce aluminates with these metals (equation 53). ... 

Interestingly, the synthesis of the heterotrimetallic alkoxides of beryllium, which began in 1985 (8), was extended in 1988 to include heterotri- and tetra-metallic alkoxides of copper (25) as well as other 3d metals (26). These last two pioneering publications were included as invited papers in two reputed international journals, leading to almost universal acceptance of the formation of the stable species called heterometallic alkoxides (3, 4, 27-33). These al-... 

The first clue to the formation of a heterotrimetallic alkoxide was, however, detected in 1985 in the case of beryllium. Its stability was initially ascribed to the small size of beryllium, which hindered the disproportionation of the species. The heterobimetallic isopropoxide (Pr-f-0)Be(/i-0-/-Pr)2Al(0-z-Pr)2 was found on the basis of NMR studies to dimerize on ageing (8) into a product that could be reported as [(0-f-Pr)2Al( -0-/-Pr)2Al(0-i -Pr)2]. This observation led to the feasibility of reactions of the following types, which resulted for the first time in 1985 in the synthesis and characterization of heterotrimetallic isopro-poxides. 

Since beryllium is smaller in size, mononuclear two-coordinate alkoxide derivatives are more likely to form. The best known examples include only aryloxide derivatives, [Be(OC6H3-/-Bu2-2,6)2] (206) [Be(OC6H2Me3-... 

Homoleptic alkoxides of lithium, beryllium, magnesium, zirco-vanadium, " chromium," rhodium," copper," cobalt, nickel" ... 

Similar to beryllium n-diaUcoxides, zinc dialkoxides are also insoluble and nonvolatile compounds. " " The alkylzinc alkoxides are, however, less polymeric and exhibit higher volatility. For example, the cryoscopic molecular weight determination in benzene indicates that methylzinc methoxide and terf-butoxide as well as ethylzinc tert-butoxide are tetrameric" with sublimation temperatures of 60, 95, and 105°C, respectively under 0.0001 mm pressure. ... 

The NMR spectra of normal alkoxides of heavier alkaline earth metals (Ca, Sr, Ba), beryllium as well as magnesium, zinc, cadmium and mercury do not appear to have been studied, probably owing to their highly polymeric nature and insolubility in common organic solvents. 

Reactions similar to those represented by Eq. (2.264) have been observed for primary and secondary alkoxides of beryllium, yttrium and lanthanides/" titanium and zirconium/" ° ° vanadium,niobium,tantalum, " uranium, iron, aluminium, gallium, silicon, germanium, as illustrated by the following equations in a few typical cases ... 

Following the procedure of Meerwein and Bersin and others, - - this method has been extended to the bimetallic alkoxides of alkali metals (Lewis bases) with those of less basic metals and metalloids, beryllium, zinc, - boron, aluminium, gallium,tin(n), " tin(iv), antimony(iii), bismuth, titanium," niobium(iv), zirconium, " thorium, niobium(v), tantalum(v) and copper. Equations (3.1)-(3.3) reflect a few typical reactions used in the synthesis of bimetallic alkoxides involving alkali metals (M) ... 

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