Consideration of spin states in determining the structure and decomposition of the transition metal pentazoles FeClN5, Fe(N5)2, Fe(H2O)4ClN5, and Fe(NH3)4ClN5

Optimised geometries and energies have been calculated for the unidentate, bidentate, and ferrocene-like structures of Fe(II) pentazoles of the form MN(5) and M'(N(5))(2), (M = FeCl, M'= Fe) using the UB3LYP DFT method with basis sets up to 6-311+G(3df) in order to study the effect of an unfilled d shell on the stability of the singlet, triplet, and quintet states; the ground state is a quintet and the quintet has a lower barrier to decomposition than the singlet.