Synthesis, characterisation and reactivity of hydrazine complexes of iron(II)

Abstract

Hydrazine complexes [Fe(R1NHNH2)(R2CN)L4][BPh4]2 1–3 and [FeH(R1NHNH2)L4]BPh4 4 [R1 = H, Me, Ph, 4-MeC6H4, 4-ClC6H4, 4-O2NC6H4 or Me2NNH2; R2 = 4-MeC6H4, Me or Ph; L = P(OEt)3, P(OMe)3 or PPh(OEt)2] were prepared by reacting nitrile complexes [Fe(R2CN)2L4][BPh4]2 and [FeH(R2CN)L4]BPh4 with an excess of the appropriate hydrazine. Their formulation and geometry in solution were established by infrared and 1H and 31P NMR spectroscopy. Amidrazone derivatives [Fe{η2-NHC(R2)NR1NH2}L4][BPh4]2 [R2 = 4-MeC6H4, Me or Ph; R1 = H or Me; L = P(OEt)3 or P(OMe)3] were obtained by allowing nitrilehydrazine complexes to react in solution and their formation, involving a nucleophilic attack of the hydrazine on the cyanide carbon atom of the R2CN ligand, is also discussed. Reaction of the arylhydrazine complexes 1–4 with Pb(O2CMe)4 at –30 °C in CH2Cl2 resulted in selective oxidation of the arylhydrazine ligand affording the aryldiazene [Fe(R1NNH)(R2CN)L4][BPh4]2 and [FeH(R1NNH)L4]BPh4 10 [R1 = aryl; L = P(OEt)3 or P(OMe)3] derivatives. Treatment of the arylhydrazine [Fe(R1NHNH2)(R2CN){P(OEt)3}4][BPh4]2 1 (R1 = Ph or 4-MeC6H4) with an excess of NEt3 resulted in a complicated reaction giving the five-co-ordinate aryldiazenido derivatives [Fe(R1N2){P(OEt)3}4]BPh4.