Beryllium–beryllium double-π bonds in the octahedral cluster of Be2(μ2-X)4 (X = Li, Cu, BeF)

Abstract

Metal–metal double-π bonding in s-block metals has not been reported until now. The octahedral clusters of Be₂(μ₂-X)₄ only possessing degenerate Be–Be double-π bonds were first achieved by an innovative concerted electron-donating strategy from the vertical plane of the Be–Be midpoint using four s¹-type electron-donating ligands. Moreover, this novel strategy is universal and independent of electronegativity. Three typical clusters were discussed herein including Be₂(BeF)₄, Be₂Li₄ and Be₂Cu₄. Especially, WBI_Be–Be in Be₂Li₄ reached up to 1.96. The significant π-bonding character was confirmed by various bond analysis strategies.