A new target for synthesis of sandwiched beryllium, magnesium, and calcium dimers: C5H7–M–M–C5H7 and C4H4P–M–M–C4H4P

Group 2 bis-element sandwiches formed by homoleptic open sandwiches with formula C5H7–M–M–C5H7 and C4H4P–M–M–C4H4P (M = Be, Mg, and Ca) have been studied at the B3LYP/cc-PVDZ and BP86/6-311G(d,p) levels of theory. The predicted M–M bond distances are much shorter than in the equivalent isolated M–M dimer and indicate substantial Be–Be, Mg–Mg, and Ca–Ca bonding. An NBO analysis shows that each M–M unit contains a single covalent bond and that the unit is linked to the open pentadienyl and phospholyl ring via ionic bonds. We thus predict that these new compounds are viable synthetic targets.