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
Homoleptic compounds
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]
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.
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. The latter is obtained from the cyclic alkyl amino carbene (CAAC) adduct of BeCl2 using KC8.[20]
One example of a Be(I)-CAAC complex was prepared by the use of TEMPO ((2,2,6,6-Tetramethylpiperidin-1-yl) oxyl).[21]
History
Dimethylberyllium was reported in 1876. A. Atterberg produced this first organoberyllium 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]
^Gad, S. C. (2014-01-01), "Beryllium", in Wexler, Philip (ed.), Encyclopedia of Toxicology (Third Edition), Oxford: Academic Press, pp. 435–437, ISBN978-0-12-386455-0, retrieved 2022-10-27
^Weiss, E. (1965). "Die kristallstruktur des diäthylmagnesiums". Journal of Organometallic Chemistry. 4 (2): 101–108. doi:10.1016/S0022-328X(00)84373-9.
^Montero-Campillo, M. Merced; Mó, Otilia; Yáñez, Manuel; Alkorta, Ibon; Elguero, José (2019-01-01), van Eldik, Rudi; Puchta, Ralph (eds.), "Chapter Three - The beryllium bond", Advances in Inorganic Chemistry, Computational Chemistry, vol. 73, Academic Press, pp. 73–121, doi:10.1016/bs.adioch.2018.10.003, S2CID140062833, retrieved 2022-10-27
^Thomas-Hargreaves, Lewis R.; Müller, Matthias; Spang, Nils; Ivlev, Sergei I.; Buchner, Magnus R. (2021). "Behavior of Lewis Bases toward Diphenylberyllium". Organometallics. 40 (22): 3797–3807. doi:10.1021/acs.organomet.1c00524.