Diberyllocene, a stable compound of Be(I) with a Be–Be bond

Abstract

The complex diberyllocene, CpBeBeCp (Cp, cyclopentadienyl anion), has been the subject of numerous chemical investigations over the past five decades yet has eluded experimental characterization. We report the preparation and isolation of the compound by the reduction of beryllocene (BeCp 2 ) with a dimeric magnesium(I) complex and determination of its structure in the solid state by means of x-ray crystallography. Diberyllocene acts as a reductant in reactions that form beryllium-aluminum and beryllium-zinc bonds. Quantum chemical calculations indicate parallels between the electronic structure of diberyllocene and the simple homodiatomic species diberyllium (Be 2 ).

Heteronuclear and Homonuclear Bimetallic Metallocenes of Alkaline Earths and Zinc

“…The ground-breaking synthesis in 2004 of a dizinc metallocene Cp*ZnZnCp* (Cp* = C 5 Me 5 – ) by Carmona and co-workers and the 2023 synthesis of CpBeBeCp by Boronski, Aldridge, and co-workers both represent fundamental advances in metallocene chemistry (Figure ) that have stimulated a great deal of interest. Isolation of Cp*ZnZnCp* heralded the introduction of a covalent metal–metal bonding that has opened diverse research opportunities in organometallic chemistry.…”

“…They found the most stable species to be the bimetallic motif, with larger metal chains preferentially losing a metal atom to form a smaller metallocene, except in the case of Be, which shows reasonable stability for all metal chains considered. This culminated in their prediction that CpBeBeCp (or Cp*BeBeCp*) should be more stable than Cp*ZnZnCp*, which was very recently realized with the isolation of CpBeBeCp …”

“…28 Chains of multidecker metallocenes were predicted to form one-dimensional (1D) nanowires, 29,30 which were recently synthesized by Huttmann et al 31 Kraus et al 32 However, stacking metallocenes is not the only method for extending their structures. The ground-breaking synthesis in 2004 of a dizinc metallocene Cp*ZnZnCp* (Cp* = C 5 ) by Carmona and co-workers 33 and the 2023 synthesis of CpBeBeCp by Boronski, Aldridge, and co-workers 34 both represent fundamental advances in metallocene chemistry (Figure 1) that have stimulated a great deal of interest. Isolation of Cp*ZnZnCp* heralded the introduction of a covalent metal−metal bonding that has opened diverse research opportunities in organometallic chemistry.…”

“…This culminated in their prediction that CpBeBeCp (or Cp*BeBeCp*) should be more stable than Cp*ZnZnCp*, which was very recently realized with the isolation of CpBeBeCp. 34 Covalent metal−metal bonding is a rapidly developing field, driven by the search for new and unusual metal−metal bonding. For alkaline earths, the field started with the seminal breakthrough in 2007 when Jones isolated a low-valent Mg(I) complex of β-diketiminato (nacnac) ligands that exhibited covalent Mg−Mg bonds.…”

“…Boronski et al 55 have isolated a complex with the first Be−Al bond and more recently the first Be−Be (CpBeBeCp) and Be−Zn (CpBeZn( Dipp nacnac)) bonds. 34 The CpBeBeCp complex has reducing properties analogous to [Mg 2 (nacnac) 2 ] compounds. Braunschweig has recently isolated several Be-chalcogen compounds with Be−S, Be−Se, and Be−Te bonds.…”