Characterization of the Carbonyl Metalates [Mn ₂ (CO) ₈ ] ²⁻ and [W ₂ (CO) ₈ ] ⁴⁻ Featuring <i>M</i> = <i>M</i> Double Bonds

The crystal structures of [Rb[2.2.2]crypt] 2 [Mn 2 (CO) 8 ] ⋅ 4NH 3 and [K[18]crown‐6] 2 K 2 [W 2 (CO) 8 ] ⋅ 14NH 3 are reported, containing the first homoleptic dinuclear carbonyl metalates featuring metal−metal double bonds. [Mn 2 (CO) 8 ] 2− and [W 2 (CO) 8 ] 4− are isostructural and isoelectronic to the elusive [Fe 2 (CO) 8 ]. Quantum chemical calculations and QTAIM analysis confirm the metallic bonding character, as well as differences in terminal and bridging carbonyl ligands.