High-spin iron(III) complexes: structural, spectroscopic, and photochemical studies

Reaction of FeCl3 with one equivalent of acac (acac = pentane-2,4-dionate) and KTpMe2 (TpMe2 = hydrotris(3,5-dimethyl-pyrazol-1-yl)borate) yielded TpMe2Fe(acac)Cl (3), which upon reaction with methanolic solution of sodium azide resulted in the formation of a six coordinate compound TpMe2Fe(acac)N3 (4) with a single azide. When the reaction of FeCl3 and KTpMe2 was performed with two equivalents of sodium azide and one equivalent of 3,5-dimethylpyrazole (PzMe2H), a six coordinate cis azide compound [TpMe2Fe(PzMe2H)(N3)2] (5) was obtained. These compounds were characterized by spectroscopic methods and single crystal X-ray crystallography. Electrochemical studies of 5 show that it can be irreversibly reduced at relatively lower potential than 4. The photolysis of 5 was performed at 77 K at different wavelengths (480, 419, and 330 nm) showing that 5 was photoreduced to a high-spin Fe(II) species instead of photooxidized to Fe(V).