Synthesis and reactivity of nitrido-rhenium and -osmium complexes with an oxygen tripod ligand

Abstract

Interaction of [ReNCl₃(PPh₃)₂] or [ReOCl₂(PPh₃)₃] with NaL_OEt (L_OEt = [Co(η⁵-C₅H₅){PO(OEt)₂}₃]) afforded [ReL_OEtN(PPh₃)Cl] 1 and [ReL_OEtOCl₂] 2, respectively. Reaction of 1 with AgBF₄ gave the nitridorhenium(VI) complex [ReL_OEtN(PPh₃)Cl]BF₄1·BF₄, which has a μ_eff of 1.8 μ_B. Treatment of 1 with MeOSO₂CF₃, PhCH₂Br or [Ph₃C]BF₄ afforded the respective organoimido species [ReL_OEt(NMe)(PPh₃)Cl][CF₃SO₃] 3, [ReL_OEt(NCH₂Ph)(PPh₃)Cl]Br 4, and [ReL_OEt(NCPh₃)(PPh₃)Cl] 5. Reaction of 1 with [Au(PPh₃)(CF₃SO₃)], [Ru(Et₂dtc)(PPh₃)₂(CO)(CF₃SO₃)], or [ReMeO₃] yielded the bimetallic nitrido complexes [Au(PPh₃){NReL_OEt(PPh₃)Cl}][CF₃SO₃] 6, [Ru(Et₂dtc)(PPh₃)(H₂O)(CO){NReL_OEt(PPh₃)Cl}][CF₃SO₃] 7 or [ReMeO₃{NReL_OEt(PPh₃)Cl}] 8, respectively. Treatment of [NBu₄ⁿ][OsNCl₄] with NaL_OEt gave [OsL_OEtNCl₂] 9. The average Os–O, Os–Cl and Os–N distances in 9 are 2.066, 2.289 and 2.58(1) Å, respectively. Reaction of 9 with PPh₃ afforded the osmium(IV) phosphoran iminate species [OsL_OEt(NPPh₃)Cl₂] 10, which has a μ_eff of 2.0 μ_B. The average Os–O, Os–Cl and Os–N distances in 10 are 2.099, 2.342, 1.893(5) Å, respectively, the Os–N–P angle being 137.5(3)°. The formal potentials of the L_OEt–Re and –Os complexes have been determined by cyclic voltammetry. On the basis of the Re^VI–Re^V formal potential, the π-donor strength was found to decrease in the order N³⁻ > [NAu(PPh₃)]²⁻ > NMe²⁻.