Synthesis, characterisation, and magnetic properties of a permethylindenyl manganocene

The heptamethylindenyl ligand (C₉Me₇^-; Ind*) has been used to synthesise the manganese complex, (η⁵-Ind*)₂Mn, by lithiation of the proligand and subsequent salt metathesis with MnCl₂. The solid state molecular structure indicates a low-spin (S = ½) ground state for the Mn²⁺ metal centre at 100 K. Solution EPR spectroscopy, solid state magnetic susceptibility measurements, and computational studies suggest the complex undergoes a thermally accessible spin-crossover to a high-spin (S = 5/2) state.