Diagonally Related s- and p-Block Metals Join Forces: Synthesis and Characterization of Complexes with Covalent Beryllium-Aluminum Bonds

Abstract

Additions of beryllium-halide bonds in the simple beryllium dihalide adducts, [BeX₂ (tmeda)] (X=Br or I, tmeda=N,N,N',N'-tetramethylethylenediamine), across the metal center of a neutral aluminum(I) heterocycle, [:Al(^Dip Nacnac)] (^Dip Nacnac=[(DipNCMe)₂ CH]^- , Dip=2,6-diisopropylphenyl), have yielded the first examples of compounds with beryllium-aluminum bonds, [(^Dip Nacnac)(X)Al-Be(X)(tmeda)]. For sake of comparison, isostructural Mg-Al and Zn-Al analogues of these complexes, viz. [(^Dip Nacnac)(X)Al-M(X)(tmeda)] (M=Mg or Zn, X=I or Br) have been prepared and structurally characterized. DFT calculations reveal all compounds to have high s-character metal-metal bonds, the polarity of which is consistent with the electronegativities of the metals involved. Preliminary reactivity studies of [(^Dip Nacnac)(Br)Al-Be(Br)(tmeda)] are reported.

Keywords: DFT calculations; aluminum; beryllium; low oxidation state; metal-metal bonding.