Preparation and reactivity of half-sandwich organic azide complexes of osmium

Abstract

Organic azide complexes [Os(η⁵-C₅H₅)(κ¹-N₃R)(PPh₃){P(OR1)₃}]BPh₄ (1, 2) [R = CH₂C₆H₅ (a), CH₂C₆H₄-4-CH₃ (b), CH(CH₃)C₆H₅ (c), C₆H₅ (d); R1 = Me (1), Et (2)] were prepared by allowing bromo-compounds [OsBr(η⁵-C₅H₅)(PPh₃){P(OR1)₃}] to react first with AgOTf and then with an excess of azide in toluene. Benzylazide complexes reacted in solution leading to imine derivatives [Os(η⁵-C₅H₅){κ¹-NHC(R2)Ar}(PPh₃){P(OR1)₃}]BPh₄ (3, 4) [R2 = H (a, b), CH₃ (c); Ar = C₆H₅, C₆H₄-4-CH₃; R1 = Me (3), Et (4)]. Phenylazide, on the other hand, reacted in solution affording the dinuclear dinitrogen complex [{Os(η⁵-C₅H₅)(PPh₃)[P(OMe)₃]}₂(μ-N₂)](BPh₄)₂ (5). Depending on the nature of the R substituent, the reaction of the p-cymene complex [OsCl₂(η⁶-p-cymene)(PPh₃){P(OEt)₃}] with RN₃ yielded imine [OsCl(η⁶-p-cymene){κ¹-NHC(H)Ar}{P(OEt)₃}]BPh₄ (6) (Ar = C₆H₄-4-CH₃) and amine derivatives [OsCl(η⁶-p-cymene)(κ¹-NH₂C₆H₅){P(OEt)₃}]BPh₄ (7). The complexes were characterised spectroscopically (IR, ¹H, ³¹P, ¹⁵N NMR) and by the X-ray crystal structure determination of [{Os(η⁵-C₅H₅)(PPh₃)[P(OMe)₃]}₂(μ-N₂)](BPh₄)₂ (5).