• Source: Organoberyllium chemistry

Organoberyllium chemistry involves the synthesis and properties of organometallic compounds featuring the group 2 alkaline earth metal beryllium (Be). The area remains less developed relative to the chemistry of other main-group elements, because Be compounds are toxic and few applications have been found.




Structure






= Homoleptic compounds

=

The coordination number of Be in organoberyllium compounds ranges from two to four.
Dimethylberyllium and dimethylmagnesium adopts the same structure. Diethylberyllium, however, does not structurally resemble diethylmagnesium (which has the same structure as dimethylmagnesium). This contrast is attributed to the small size of Be relative to its heavier congener Mg: Be is one of the smallest atoms on the periodic table. Dineopentylberyllium and many other dialkyl derivatives has been reported.
The phenyl derivative is represented by trimeric Be3Ph6. A terphenyl derivative is known. With bulky aryl ligands three-coordination is observed, see Be(mesityl)2O(C2H5)2.
Organoberyllium compounds are typically prepared by transmetallation or alkylation of beryllium chloride.




= Beryllocene

=

Beryllocene features both pi- and sigma-bonded cyclopentadienyl ligands.
It is prepared from BeCl2 and potassium cyclopentadienide:

2 K[Cp] + BeCl2 → [Cp]2Be + 2 KCl




= Mixed ligand compounds

=
Many mixed ligand complexes are simply formed by addition of Lewis bases to diaryl and dialkylberyllium compounds. Many derivatives are known of the type BeR2L2 and BAr2L2 are known where L = thioether, pyridine, NHC, and 1,4-Diazabutadienes.
Beryllium forms a variety of complexes with N-hetereocyclic carbenes (NHCs). Beryllium complexes of cyclic alkyl amino carbene (CAAC) ligands have the formula (CAAC)BeR2). A CAAC ligand coordinates a 2 electron -1 charge into the beryllium center. CAAC has an "amino" substituent and an "alkyl" sp3 carbon atom. CAACs are very good σ donors (higher HOMO) and π acceptors (lower LUMO) compared to NHCs. In addition, the lower heteroatom stability of the carbene center in CAAC compared to NHC results in a lower ΔE.




Low oxidation beryllium chemistry


While Be(II) is one of the common oxidation state for Be, compounds containing Be(I) and Be(0) have been described..

One example of a Be(I) was a CAAC ligand has been reported in the form of a radical cation. The reduction of Be(II) to Be(I) involved the use of TEMPO ((2,2,6,6-Tetramethylpiperidin-1-yl) oxyl).




History


Dimethylberyllium was reported in 1876. A. Atterberg produced this first organoBe compound by treatment of dimethylmercury with elemental beryllium.
The alkylation of beryllium halides was studied by H. Gilman. Early systematic work was conducted by G. E. Coates.




See also


Group 2 organometallic chemistry
Beryllium




References

Kata Kunci Pencarian:

• Organoberyllium chemistry
• Group 2 organometallic chemistry
• Organometallic chemistry
• Beryllium
• Robert Gilliard
• Beryllocene