On the unprecedented level of dinitrogen activation in the calix[4]arene complex of Nb(III)

The calix[4]arene niobium(iii) complex ([L]Nb-NN-Nb[L] where [L] = p-tert-butylcalix[4]arene), reported to bind N2 in a μ2-linear dimeric capacity and to activate the N2 triple bond to 1.39 Å, corresponding to the longest N2 bond known in the end-on co