Synthesis and reactivity of hydrazine complexes of iridium(III)

Abstract

Hydride complexes IrHCl₂[PPh(OEt)₂]L₂1, 3 and IrHCl₂[P(OEt)₃]L₂2, 4 (L = PPh₃ or AsPh₃) were prepared by substituting one phosphine or arsine ligand in IrHCl₂L₃ with the appropriate phosphite. Treatment of hydrides 1–4 first with triflic acid (CF₃SO₃H) and then with hydrazines gave [IrCl₂(RNHNH₂){PPh(OEt)₂}L₂]BPh₄5, 7 and [IrCl₂(RNHNH₂){P(OEt)₃}L₂]BPh₄6, 8 (R = H, Me, Ph or C₆H₄NO₂-4). Hydride–hydrazine complexes [IrH₂(RNHNH₂)(PPh₃)₃]BPh₄9 and [IrHCl(RNHNH₂)(PPh₃)₂]BPh₄10 (R = H, Me or Ph) were also prepared by allowing IrH₃(PPh₃)₃ or IrH₂Cl(PPh₃)₃ to react sequentially first with CF₃SO₃H or HBF₄·Et₂O and then with the appropriate hydrazine. All complexes were fully characterised by IR and NMR spectroscopy and their geometry in solution was also established. Oxidation with Pb(OAc)₄ at −30 °C of arylhydrazines [IrCl₂(ArNHNH₂)L′L₂]BPh₄5–8 [L′ = PPh(OEt)₂ or P(OEt)₃; Ar = Ph] afforded stable aryldiazene derivatives [IrCl₂(ArNNH){PPh(OEt)₂}L₂]BPh₄11, 13 and [IrCl₂(ArNNH){P(OEt)₃}L₂]BPh₄12, 14. By contrast, treatment with Pb(OAc)₄ at −30 °C of methylhydrazine complexes [IrCl₂(MeNHNH₂)L′L₂]BPh₄ gave hydrides IrHCl₂L′L₂. Aryldiazene complexes [IrCl₂(ArNNH)L′L₂]BPh₄11–14 and [{IrCl₂L′L₂}₂(μ-HNNAr–ArNNH)](BPh₄)₂15–18 [Ar = Ph or C₆H₄Me-4; Ar–Ar = 4,4′-C₆H₄–C₆H₄ or 4,4′-(2-Me)C₆H₃–C₆H₃(Me-2)] were also prepared by allowing hydride species IrHCl₂L′L₂1–4 to react with the appropriate aryldiazonium cations in acetone at −80 °C. Their characterisation by IR and NMR spectroscopy (with ¹⁵N isotopic substitution) is discussed.