Carbonyl Metalates in Liquid Ammonia: Reduction of Mn ₂ (CO) ₁₀ down to [Mn(CO) ₄ ] ³⁻

The crystal structures of three compounds derived from the reduction of Mn 2 (CO) 10 with potassium in liquid ammonia solution with and without the presence of [2.2.2]crypt ([2.2.2]crypt = 4,7,13,16,21,24‐Hexaoxa‐1,10‐diazabicyclo[8.8.8]‐hexacosane) is reported. For the formation of [K([2.2.2]crypt)] 2 [HMn(CO) 4 ] 2 NH 3 and K 3 [Mn(CO) 4 ] 2 NH 3 , liquid ammonia plays a crucial role as a solvent providing solvated electrons used for the reduction as well as for the stabilization of highly charged manganese carbonylates in ammoniate crystals. The isolation of [K([2.2.2]crypt)][Mn(CO) 4 (NH 3 )] 3 NH 3 offers an insight into a possible intermediate during the reduction from [Mn(CO) 5 ] − to [Mn(CO) 4 ] 3− via the ammonia alkali metal route.