Reductive activation of N₂ using a calcium/potassium bimetallic system supported by an extremely bulky diamide ligand

An extremely bulky xanthene bridged diamide ligand (^TCHPNON = 4,5-bis(2,4,6-tricyclohexylanilido)-2,7-diethyl-9,9-dimethyl-xanthene) has been developed and used to prepare two monomeric diamido-calcium complexes [(^TCHPNON)Ca(D)_n] (D = THF, n = 2, 3; D = toluene, n = 1, 4). Reduction of 4 with 5% w/w K/KI under an N₂ atmosphere gave the first well-defined, hetero-bimetallic s-block complex of activated dinitrogen, [{K(^TCHPNON)Ca}₂(μ-η²:η²-N₂)] 5, presumably via a transient calcium(I) intermediate.