Organoberyllium chemistry

Structure of "diphenyl beryllium, which has the formula Be3(C6H5)6.[1]

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 structure of dimethylberyllium.

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

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] 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.

Coordination of a CAAC ligand to a Be complex with R not limited for coordination with Be

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..[20]

This reaction is shown when a CAAC ligand is coordinated with a BeCl2 and using KC8 to form a zero oxidation beryllium complex. This work was done by Prof Braunschweig to create the first neutral Be complex the R group includes Me and (CH2)5 and Dipp is otherwise known as 2,6-diisopropylphenyl.

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).

Reaction shown is radical cation reaction from a Be(II) CAAC compound to a Be(I) CAAC compound.

History

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]

See also

References

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  2. ^ a b Coates, G. E.; Morgan, G. L. (1971-01-01), Stone, F. G. A.; West, Robert (eds.), Organoberyllium Compounds, Advances in Organometallic Chemistry, vol. 9, Academic Press, pp. 195–257, doi:10.1016/S0065-3055(08)60052-0, ISBN 9780120311095, retrieved 2022-11-08
  3. ^ Gad, S. C. (2014-01-01), "Beryllium", in Wexler, Philip (ed.), Encyclopedia of Toxicology (Third Edition), Oxford: Academic Press, pp. 435–437, ISBN 978-0-12-386455-0, retrieved 2022-10-27
  4. ^ Nembenna, Sharanappa; Sarkar, Nabin; Sahoo, Rajata Kumar; Mukhopadhyay, Sayantan (2022-01-01), Parkin, Gerard; Meyer, Karsten; O’hare, Dermot (eds.), "2.03 - Organometallic Complexes of the Alkaline Earth Metals", Comprehensive Organometallic Chemistry IV, Oxford: Elsevier, pp. 71–241, ISBN 978-0-323-91350-8, retrieved 2022-10-27
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  6. ^ Weiss, E. (1965). "Die kristallstruktur des diäthylmagnesiums". Journal of Organometallic Chemistry. 4 (2): 101–108. doi:10.1016/S0022-328X(00)84373-9.
  7. ^ 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, S2CID 140062833, retrieved 2022-10-27
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  12. ^ Almenningen, Arne; Haaland, Arne; Lusztyk, Janusz (1979-05-08). "The molecular structure of beryllocene, (C5H5)2Be. A reinvestigation by gas phase electron diffraction". Journal of Organometallic Chemistry. 170 (3): 271–284. doi:10.1016/S0022-328X(00)92065-5. ISSN 0022-328X.
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  18. ^ Buchner, Magnus R.; Müller, Matthias; Rudel, Stefan S. (2017-01-19). "Beryllium Phosphine Complexes: Synthesis, Properties, and Reactivity of (PMe 3 ) 2 BeCl 2 and (Ph 2 PC 3 H 6 PPh 2 )BeCl 2". Angewandte Chemie International Edition. 56 (4): 1130–1134. doi:10.1002/anie.201610956. PMID 28004465.
  19. ^ Schuster, Julia K.; Roy, Dipak Kumar; Lenczyk, Carsten; Mies, Jan; Braunschweig, Holger (2019-02-18). "New Outcomes of Beryllium Chemistry: Lewis Base Adducts for Salt Elimination Reactions". Inorganic Chemistry. 58 (4): 2652–2658. doi:10.1021/acs.inorgchem.8b03263. ISSN 0020-1669. PMID 30707568. S2CID 73424673.
  20. ^ Arrowsmith, Merle; Braunschweig, Holger; Celik, Mehmet Ali; Dellermann, Theresa; Dewhurst, Rian D.; Ewing, William C.; Hammond, Kai; Kramer, Thomas; Krummenacher, Ivo; Mies, Jan; Radacki, Krzysztof; Schuster, Julia K. (2016-06-06). "Neutral zero-valent s-block complexes with strong multiple bonding". Nature Chemistry. 8 (9): 890–894. Bibcode:2016NatCh...8..890A. doi:10.1038/nchem.2542. ISSN 1755-4349. PMID 27334631.
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