Synthesis and properties of the bis(µ-thiosulphato-S)-bis(dinitrosylferrate)(2–) anion. Crystal and molecular structure of bis[bis(triphenylphosphoranylidene)-ammonium] bis(µ- thiosulphato-S)-bis(dinitrosylferrate)

Abstract

Salts of the bis(µ-thiosulphato-S)-bis(dinitrosylferrate)(2–) anion [Fe₂(S₂O₃)₂(NO)₄]^2– can be prepared by reaction of iron(II)/thiosulphate mixtures either with nitric oxide or with sodium nitrite: the preparation using nitrite provides a convenient route to the ¹⁵N labelled anion [Fe₂(S₂O₃)₂(¹⁵NO)₄]^2–. The anion reacts readily with thiols RSH to provide good yields of [Fe₂(SR)₂(NO)₄]. Crystals of [N(PPh₃)₂]₂[Fe₂(S₂O₃)₂(NO)₄] are triclinic, a= 10.999(5), b= 12.748(4), c= 14.020(7)Å, α= 67.13(4), β= 83.31(4), γ= 93.87(3)°, space group P with Z= 1: the structure was solved using diffractometer data and refined to an R value of 0.034. The anion lies across a centre of inversion, and hence adopts the trans conformation. The ¹⁵N n.m.r. spectrum of [Fe₂(S₂O₃)₂(¹⁵NO)₄]^2– shows the presence of only the trans conformer in solution, and that upon exposure to air [Fe₂(S₂O₃)₂(¹⁵NO)₄]^2– is readily converted into [Fe₄S₃(¹⁵NO)₇]^–.