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. © 2022 The Royal Society of Chemistry.