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Organoberyllium Complex in Main Group Chemistry From Wikipedia, the free encyclopedia
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]
The coordination number of Be in organoberyllium compounds ranges from two to four.[4]
Dimethylberyllium and dimethylmagnesium adopts 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 features both pi- and sigma-bonded cyclopentadienyl ligands.[11][12][13] It is prepared from BeCl2 and potassium cyclopentadienide:
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] 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.[19] 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.
While Be(II) is one of the common oxidation state for Be, compounds containing Be(I) and Be(0) have been described..[20]
One example of a Be(I) was a CAAC ligand has been reported in the form of a radical cation.[21] The reduction of Be(II) to Be(I) involved the use of TEMPO ((2,2,6,6-Tetramethylpiperidin-1-yl) oxyl).
Dimethylberyllium was reported in 1876. A. Atterberg produced this first organoBe compound by treatment of dimethylmercury with elemental beryllium.[22] The alkylation of beryllium halides was studied by H. Gilman.[23][10] Early systematic work was conducted by G. E. Coates.[2]
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