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

Reactions of the beryllium dihalide complexes [BeX₂ (OEt₂ )₂ ] (X=Br or I) with N,N,N',N'-tetramethylethylenediamine (TMEDA), a series of diazabutadienes, or bis(diphenylphosphino)methylene (DPPM) have yielded the chelated complexes, [BeX₂ (TMEDA)], [BeX₂ {(RN=CH)₂ }] (R=tBu, mesityl (Mes), 2,6-diethylphenyl (Dep) or 2,6-diisopropylphenyl (Dip)), and the non-chelated system, [BeI₂ (κ¹ -P-DPPM)₂ ]. Reactions of lithium or potassium salts of a variety of β-diketiminates have given both three-coordinate complexes, [{HC(RCNAr)₂ }BeX] (R=H or Me; Ar=Mes, Dep or Dip; X=Br or I); and four-coordinate systems, [{HC(MeCNPh)₂ }BeBr(OEt₂ )] and [{HC(MeCNDip)(MeCNC₂ H₄ NMe₂ }BeI]. Alkali metal salts of ketiminate, guanidinate, boryl/phosphinosilyl amide, or terphenyl ligands, lead to dimeric [{BeI{μ-[(OCMe)(DipNCMe)]CH}}₂ ], and monomeric [{iPr₂ NC(NMes)₂ }BeI(OEt₂ )], [κ² -N,P-{(HCNDip)₂ B}(PPh₂ SiMe₂ )NBeI(OEt₂ )] and [{C₆ H₃ Ph₂ -2,6}BeBr(OEt₂ )], respectively. Compound [{HC(MeCNPh)₂ }BeBr(OEt₂ )] undergoes a Schlenk redistribution reaction in solution, affording the homoleptic complex, [{HC(MeCNPh)₂ }₂ Be]. The majority of the prepared complexes have been characterized by X-ray crystallography and multi-nuclear NMR spectroscopy. The structures and stability of the complexes are discussed, as is their potential for use as precursors in poorly developed low oxidation state beryllium chemistry.