Organoberyllium chemistry

Organoberyllium chemistry involves the synthesis and properties of organometallic compounds featuring the group 2 alkaline earth metal beryllium (Be).^[2] 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.^[3]

Structure of diphenylberyllium, which has the formula Be₃(C₆H₅)₆.^[1]

Structure

Homoleptic compounds

The structure of dimethylberyllium.

The coordination number of Be in organoberyllium compounds ranges from two to four.^[4]

Dimethylberyllium and dimethylmagnesium adopt the same structure.^[5] Diethylberyllium, however, does not structurally resemble diethylmagnesium (which has the same structure as dimethylmagnesium).^[6] 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.^[7] Dineopentylberyllium and many other dialkyl derivatives has been reported.^[8]

The phenyl derivative is represented by trimeric Be₃Ph₆.^[1] A terphenyl derivative is known.^[9] With bulky aryl ligands three-coordination is observed, see Be(mesityl)₂O(C₂H₅)₂.^[8]

Organoberyllium compounds are typically prepared by transmetallation or alkylation of beryllium chloride.^[10]

Beryllocene

This structure of Be(C₅H₅)₂

Beryllocene features both pi- and sigma-bonded cyclopentadienyl ligands.^[11][12][13] 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,^[14] and 1,4-Diazabutadienes.^[15] Beryllium forms a variety of complexes with N-hetereocyclic carbenes (NHCs).^[16][17][18]

Low oxidation beryllium chemistry

While the +2-oxidation state is by far the most common for Be, compounds containing Be(I) and Be(0) have been described. A number of beryllium complexes with cyclic alkyl amino carbene (CAAC) ligands have been proposed to feature low-oxidation state beryllium centres.^[19][20] However, these low-oxidation state formulations have been contested due to the redox non-innocence of CAAC ligands.^[21][22][23] Unambiguous low-oxidation state organo-beryllium complexes with Be–Be bonds have been synthesized by the group of Simon Aldridge.^[24][25]

History

Dimethylberyllium was reported in 1876. A. Atterberg produced this first organoberyllium compound by treatment of dimethylmercury with elemental beryllium.^[26] The alkylation of beryllium halides was studied by H. Gilman.^[27][10] Early systematic work was conducted by G. E. Coates.^[2]

See also

• Group 2 organometallic chemistry
• Beryllium