The Iron Hydrido Complex [FeH(dppe) 2 ] + : Solution and Solid‐State Reactivity with Dinitrogen

The blue compound [FeH(dppe) 2 ]BPh 4 ( 1 ) (dppe = 1,2‐bis(diphenylphosphino)ethane) is investigated by optical absorption, vibrational, NMR and Mössbauer spectroscopy as well as magnetic susceptibility measurements. In the solid state, 1 is found to be paramagnetic (S=1) whereas in tetrahydrofuran (thf) solution it is diamagnetic. Importantly, 1 reacts with dinitrogen in thf solution and in the solid state to give the yellow and green dinitrogen complexes 2a and 2b , respectively, both of which have the formula [FeH(N 2 )(dppe) 2 ]BPh 4 . Apart from their colour and optical spectroscopic properties, the dinitrogen compounds 2a and 2b also differ in their magnetic, Mössbauer and vibrational properties. The N‐N stretching frequency of 2a is found at 2120 cm −1 whereas 2b exhibits an N‐N stretching vibration of 2145 cm −1 . Moreover, 2a is diamagnetic whereas 2b is paramagnetic. DFT is employed to determine the relative energies and structure of 1 and its dinitrogen adducts in the singlet and triplet state.