Crystal beryllium compounds

The bis(propynyl)beryllium compound [Be(C=CMe)2NMe3]2 is unusual in crystallizing with two types of dimeric molecule in the lattice, one of which has a diamond-shaped (Be-C)2 ring very similar to that of 31. The other, structure 32, has a nearly rectangular (Be-C)2 ring, explicable in terms of donation of charge from the alkynyl triple bond into the available metal orbital. 

The physicochemical properties of beryllium compounds and alloys have been reviewed subjects include phase diagrams, crystal structure, and density data on alloys and compounds, with a special section devoted entirely to halides and chalcogenides. ... 

Beryllium fluoride is hygroscopic and highly soluble in water, although its dissolution rate is slow. FluoroberyUates can be readily prepared by crystallization or precipitation from aqueous solution. Compounds containing the BeP ion are the most readily obtained, though compounds containing other fluoroberyUate ions can also be obtained, eg, NH BeF, depending upon conditions. 

It is also shown that theoretically a binary compound should have the sphalerite or wurzite structure instead of the sodium chloride structure if the radius ratio is less than 0.33. The oxide, sulfide, selenide and telluride of beryllium conform to this requirement, and are to be considered as ionic crystals. It is found, however, that such tetrahedral crystals are particularly apt to show deformation, and it is suggested that this is a tendency of the anion to share an electron pair with each cation. 

In a search for CVD precursors for beryllium, the air sensitive, volatile solid CpBe(SiMe3) 17 was prepared from the reaction of Li[SiMe3] with CpBeCl in pentane.62 Characterized with single crystal X-ray diffraction, multinuclear NMR, and mass spectra, the compound displays a Be-Si bond length of 2.185(2) A that is somewhat longer than the sum of covalent radii (2.01 A). The lengthening is similar to that observed in the related Be(Si(/-Bu)3)2 (Be-Si = 2.193(1) A),63 so there is not a pronounced effect from the Cp ligand on the Be-Si interaction. 

TABLE A2 Thermochemical Data of Selected Chemical Compounds Beryllium (Be), crystal-liquid, molecular weight = 9.01218... 

A further point of interest is that in both the dimeric and trimeric species shown, the beryllium atom still has a vacant orbital available which may be used in adduct formation without disruption of the electron-deficient bond. This type of behavior leads to the formation of dimers with four-coordinate beryllium atoms, e.g., structure XX (86). This structure has been determined in the solid state and shows that the phenylethynyl-bridging group is tipped to the side, but to a much smaller extent than observed in the aluminum derivative (112). One cannot be certain whether the distortion in this case is associated with a it - metal interaction or is simply a result of steric crowding, crystal packing, or the formation of the coordination complexes. Certainly some differences must have occurred since both the Be—Be distance and Be—C—Be angle are substantially increased in this compound relative to those observed in the polymer chain. 

Sublimation. Perform the experiment in a fume cupboard ) Put the beryllium oxyacetate crystals into a test tube. Slightly tilt the tube with its mouth downward and carefully heat it in the flame of a burner. What happens What is the composition of the substance deposited on the tube walls Examine the crystals of the precipitated and sublimed beryllium oxyacetate under a microscope. What can this compound be used for in the technology of beryllium ... 

The study of coordination compounds of the lanthanides dates in any practical sense from around 1950, the period when ion-exchange methods were successfully applied to the problem of the separation of the individual lanthanides,131-133 a problem which had existed since 1794 when J. Gadolin prepared mixed rare earths from gadolinite, a lanthanide iron beryllium silicate. Until 1950, separation of the pure lanthanides had depended on tedious and inefficient multiple crystallizations or precipitations, which effectively prevented research on the chemical properties of the individual elements through lack of availability. However, well before 1950, many principal features of lanthanide chemistry were clearly recognized, such as the predominant trivalent state with some examples of divalency and tetravalency, ready formation of hydrated ions and their oxy salts, formation of complex halides,134 and the line-like nature of lanthanide spectra.135... 

The crystal structure of beryllium carbide is cubic, density = 2.44 g/mL. The melting point is 2250—2400°C and the compound dissociates under vacuum at 2100°C (1). This compound is not used industrially, but Be2C is a potential first-wall material for fusion reactors, one on the very limited list of possible candidates (see Fusion energy). 

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