Reduction of azobenzene by neodymium(II), dysprosium(II), and thulium(II) diiodides

The diiodides of divalent neodymium (1), dysprosium (2), and thulium (3) LnI2 readily reduce azobenzene under ambient conditions to give binuclear complexes [LnI(THF)2]2(N2Ph2)2 (Ln=Nd (4), Dy (5), Tm (6)). Magnetic measurements and X-ray structural analyses of 5 and 6 revealed that the bridging N2Ph2 ligands are dianions bounded to the trivalent lanthanoid. The complexes displayed photochromic properties. Ytterbium iodide YbI2(THF)2 reacts with N2Ph2 at 80 °C yielding the known [YbI(THF)3]2(N2Ph2)2 (7).