 In line with the general method, bis(trimethylsilyl)amides of transition metals are prepared by a reaction between the metal halides (typically chlorides) and sodium bis(trimethylsilyl)amide, some variation does exist however, for instance the synthesis of blue Ti(N(SiMe3)2)3 using the soluble precursor TiCl3(Et3N)3.The melting and boiling points of the complexes decrease across the series, with Group 12 metals being sufficiently volatile to allow purification by distillation.Iron complexes are notable for having been isolated in both the ferrous (II) and ferric (III) oxidation states.