Side-on Bound Diazene and Hydrazine Complexes of Ruthenium

The reaction of cis-[RuCl₂(PP)₂] (PP = depe, dmpe) with hydrazine afforded end-on bound ruthenium(II) hydrazine complexes. Treatment of the hydrazine complexes with strong base afforded the side-on bound ruthenium(0) diazene complexes cis-[Ru(η²-NHNH)(PP)₂]. Treatment of cis-[Ru(η²-NHNH)(depe)₂] with weak acid under chloride-free conditions afforded the side-on bound hydrazine complex cis-[Ru(η²-N₂H₄)(depe)₂]²⁺. These are the first reported side-on bound diazene and hydrazine complexes of ruthenium, and they have been characterized by NMR spectroscopy (¹H, ³¹P, ¹⁵N) and by X-ray crystallography. The interconversion between the ruthenium diazene and the ruthenium hydrazine by acid−base treatment was reversible.