Beryllium Halide Complexes Incorporating Neutral or Anionic Ligands: Potential Precursors for Beryllium Chemistry

Abstract

Reactions of the berylliumd ihalidec omplexes [BeX 2 (OEt 2 ) 2 ]( X= Br or I) with N,N,N',N'-tetramethylethylenediamine (TMEDA), as eries of diazabutadienes, or bis(diphenylphosphino)methylene (DPPM) have yielded the chelated complexes, [BeX 2 (TMEDA)],[ BeX 2 {(RN = CH) 2 }] (R = tBu, mesityl (Mes), 2,6-diethylphenyl (Dep) or 2,6-diisopropylphenyl (Dip)), and the non-chelated system, [BeI 2 (k 1 -P-DPPM) 2 ]. Reactions of lithium or potassium salts of av ariety of b-diketiminates have given both three-coordinate complexes, [{HC(RCNAr) 2 }BeX] (R = Ho rM e; Ar = Mes, Dep or Dip;X= Br or I);a nd four-coordinate systems, [{HC(MeCNPh) 2 }-BeBr(OEt 2 )] and [{HC(MeCNDip)(MeCNC 2 H 4 NMe 2 }BeI].A lkali metal salts of ketiminate, guanidinate, boryl/phosphinosilyl amide, or terphenyl ligands, lead to dimeric[ {BeI{m-[(OCMe)(-DipNCMe)]CH}} 2 ], and monomeric [{iPr 2 NC(NMes) 2 }BeI(OEt 2 )], [k 2 -N,P-{(HCNDip) 2 B}(PPh 2 SiMe 2 )NBeI(OEt 2 )] and [{C 6 H 3 Ph 2 -2,6}BeBr(OEt 2 )],r espectively.C ompound [{HC(MeCNPh) 2 }-BeBr(OEt 2 )] undergoes aS chlenk redistributionr eaction in solution, affordingt he homoleptic complex, [{HC(MeCNPh) 2 } 2 Be].T he majority of the prepared complexes have been characterizedb yX -ray crystallography and multinuclear NMR spectroscopy.T he structures and stability of the complexes are discussed, as is their potential for use as precursors in poorly developed low oxidationstate beryllium chemistry.

Recent Contributions to the Coordination Chemistry of Beryllium

“…[22] The related diethyle therates of BeCl 2 , [24] BeBr 2 , [25] and BeI 2 [14] can be either prepared by dissolving the corresponding beryllium halide in diethyle ther or through the already mentioned reactiono fb eryllium metal with bromine or iodine. [13] Thes tructure of the etherates is similar to that of the above-mentioned compounds. [14,24,25] The ether adducts are soluble in coordinating and aromatic solvents and can be reacted in salt-metathesis reactionsw ith one or two equivalents of lithium aryls to the corresponding monohalide monoaryl Magnus R. Buchner studied chemistry at the Technische UniversitätM ünchen whereh er eceivedh is Ph.D. in 2011u nder the supervision of Klaus Ruhland.…”

“…The conversion is relativelys traightforward and beryllium-metal powder can be reactedi nawide variety of coordinating solvents with bromine or iodinet ot he corresponding solventa dducts of beryllium bromide and iodide, respectively. Through this route diethyle therates of BeBr 2 (1a) [13] and BeI 2 (1b) [13,14] and the acetonitrile complex of BeBr 2 (2)were synthesized (Scheme 1). [15] However,t his alwaysl eads to solvent coordinated complexesa nd can resulti nc ationic berylliumc omplexes (3)w hen strongly coordinatings olvents are used.…”

“…Scheme1.Synthesis of solventa dducts of beryllium bromide andiodide from beryllium metal (a:X= Br,b:X= I). [13][14][15][16] Figure 1. Beryllium coordination compounds with monodentate O-donorligands.…”

“…Beryllium coordination compounds with monodentate O-donorligands. [13,22,24,26,27] (7), [13] or diarylberyllium (8)c ompounds. [26] Accordingly,a lso lithium phenolates can be reacted with BeCl 2 in diethyle ther to beryllium phenolates (9).…”

“…[24] In all three cases the beryllium atom is threefold coordinatedw ith an ether serving as the third ligand. [13,24,25] Althoughi na ll these reactions diethyle ther acts as an innocent ligand that facilitates solubility in various solvents, the presence of strong N-donor ligandsl ike piperidine or pyrazole leads to cleavage of an ether CÀOb ond through an unknown mechanism and formation of dinuclear, alkoxy bridged complexes like piperidine adduct 10. [27] In am ore detailed study on the steric and electronic influence of carboxylic acid esters coordinated to BeCl 2 it was shown that the less bulky the ligand, the more reactive are the correspondingc omplexes, as would be expected.…”