Reactivity studies on [Cp'Fe(μ-I)]: nitrido-, sulfido- and diselenide iron complexes derived from pseudohalide activation.

The iron half-sandwich [Cp'Fe(μ-I)] (Cp' = 1,2,4-(MeC)CH, ) reacts with the pseudohalides NCO, SCN, SeCN and N to give [Cp'Fe(μ-NCO)] (), [Cp'Fe(μ-S)] (), [Cp'Fe(μ-Se)] () and [Cp'Fe(μ-N)] (), respectively. Various spectroscopic techniques including X-ray diffraction, solid-state magnetic susceptibility studies and Fe Mössbauer spectroscopy were employed in the characterization of these species. Mössbauer spectroscopy shows a decreasing isomer shift with increasing formal oxidation state, ranging from Fe(ii) to Fe(iv), in complexes to . The sulfido-bridged dimer exhibits strong antiferromagnetic coupling between the Fe(iii) centers. This leads to temperature-independent paramagnetism (TIP) at low temperature, from which the energy gap between the ground and the excited state can be estimated to be 2 = 700 cm. The iron(iv) nitrido complex [Cp'Fe(μ-N)] () shows no reactivity towards H (10 atm), but undergoes clean reactions with CO (5 bar) and XylNC (Xyl = 2,6-MeCH) to form the diamagnetic isocyanate and carbodiimide complexes [Cp'Fe(CO)(NCO)] () and [Cp'Fe(CNXyl)(NCNXyl)] (), respectively. All compounds were fully characterized, and density functional theory (DFT) computations provide useful insights into their formation and the electronic structures of complexes and .