Beryllium compounds structure

Beryllium compounds have a pronounced covalent character, and the structural... 

The zinc complex formed with V,V -diphenylformamidinate is structurally analogous to the basic zinc acetate structure, as [Zn4(/i4-0)L6], and the basic beryllium acetate structure. It is prepared by hydrolysis of zinc bis(diphenylformamidinate).184 Mixed metal zinc lithium species were assembled from dimethyl zinc, t-butyl lithium, V.iV -diphenylbenzamidine and molecular oxygen. The amidinate compounds formed are dependent on the solvent and conditions. Zn2Li2 and... 

The structure of dimethylberyllium is similar to that of trimethylaluminum except for the fact that the beryllium compound forms chains, whereas the aluminum compound forms dimers. Dimethylberyllium has the structure shown in Figure 12.3. The bridges involve an orbital on the methyl groups overlapping an orbital (probably best regarded as sp3) on the beryllium atoms to give two-electron three-center bonds. Note, however, that the bond angle Be-C-Be is unusually small. Because beryllium is a Lewis acid, the polymeric [Be(CH3)2] is separated when a Lewis base is added and adducts form. For example, with phosphine the reaction is... 

Only three beryllium compounds have been structurally characterized, the three-coordinate monomers [Be(SMes )2(thf)]73 and [Be(SMes )(SCgH3-2,6-Mes2)(OEt2)]74 and the four-coordinate [ Be(SPh)2(py)(NH3) 2(18-crown-6)] (7).75... 

Only a limited number of structural studies have been reported on beryllium compounds. The simple alkyls appear to be polymeric with chain structures as shown in XVI (109). For comparison, the structure of di-(t-butyl)beryllium (XVII) is shown as determined from electron diffraction studies (6). In this case, the compound is a linear monomeric species with a Be—C bond length of 1.699 A. Similarly, dimethylberyl-lium has a Be—C bond distance of 1.70 A in the gas phase (5). Comparison of these beryllium structures with the polymer shows that the Be—C distance in the bridge is considerably greater than that in a normal Be—C single bond, a result similar to that observed for the aluminum derivatives. 

Because of its toxicity, the number of well-characterized beryllium compounds of all types is much lower than that of the other alkaline earth metals. The largest number of the pubhshed berylhum structures involve oxygen donor ligands, " and beryllium amides have been reviewed, at least in part, under the aegis of wider-ranging surveys - of group 2... 

Beryllium compounds have a pronounced covalent character, and the structural unit is commonly tetrahedral. The small size of the magnesium cation results in a thermally stable oxide with low solubility in water. 

Pyrazolylborates have now been also used to extract Mg, Ca, Sr, and Be from aqueous solutions into CH2C12 selectivity depends on the nature of the ligand. The structures of [HBpz3]2M, M = Mg, Ca have distorted octahedral coordination with tridentate N bonding the beryllium compounds discussed earlier were tetrahedral. 

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 octet rule predicts that atoms form enough covalent bonds to surround themselves with eight elechons each. When one atom in a covalently bonded pair donates two electrons to the bond, the Lewis structure can include the formal charge on each atom as a means of keeping track of the valence electrons. There are exceptions to the octet rule, particularly for covalent beryllium compounds, elements in Group 3A, and elements in the third period and beyond in the periodic table. 

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. ... 

Some of the ionic M(C5H5)2 compounds have sandwich structures, like that of ferrocene. This is not surprising since such an arrangement is electrostatically the most favorable structure is not a criterion of bond type in cyclopentadienyl-metal systems. The beryllium compound, Be(C5H5)2 has a most interesting unsymmetrical sandwich structure (23-XIV), in which... 

Structure. Older concepts picturing the basic beryllium compounds as derivatives of condensed acids or as structural analogs of the true basic salts of the other elements have been discarded in favor of unitary structures comparable with those ascribed to other strictly covalent compounds. 

Beryllium compounds have polymeric structures due to the formation of three-center bonds, Be-C —Be (Figure 1.2). Be(CH3)2 is a Ae compound. As a result of coordinating Lewis bases, it achieves the octet structure. 

Fig. lr.1-132 The Brillouin zone of the wurtzite lattice Table ir.1-101 Band structures of beryllium compounds... 

---