Molecular rearrangements of diynes coordinated to triosmium carbonyl clusters: reactions of [Os3(μ-H)2(CO)10] and [Os3(CO)10(MeCN)2] with 1,4-dipyridylbuta-1,3-diyne

Abstract

Reaction of [Os₃(μ-H)₂(CO)₁₀] with 1,4-dipyridylbuta-1,3-diyne yields two clusters, [Os₃(μ-H)(CO)₁₀{μ-η¹:η¹-(C₈H₅N)–C–(C₅H₄N)}] 1 and [Os₃(μ-H)(CO)₁₀-{μ₃-η¹:η¹:η¹-(C₅H₄N)–C–C(C₈H₆N)}] 2, in which the diyne has rearranged to form a substituted indolizine ring system. Complex 1 converts slowly to 2 at room temperature, and may be decarbonylated to yield [Os₃(μ-H)(CO)₉{μ-η¹:η²:η¹-(C₈H₅N)–C–(C₅H₄N)}] 3. An analogous reaction involving [Os₃(CO)₁₀(MeCN)₂] generates three products, [Os₃(μ-H)(CO)₁₀{μ-η¹:η¹-(NC₅H₃)–C₂C₂–(C₅H₅N)}] 4 and [{Os₃(μ-H)(CO)₁₀}₂{μ-η¹:η¹-(NC₅H₃)–C₂–}₂] 5, both coordinated via orthometallated pyridyl rings, and a minor product [{Os₃(CO)₁₀}₂{μ₃-η¹:η¹:η¹-C₂-(NC₅H₄)}₂] 6, coordinated via μ-carbene and σ-N interactions, the linking ligand retaining its central CC bond. Complex 4 reacts with [Os₃(μ-H)₂(CO)₁₀] to form the linked cluster [{Os₃(μ-H)(CO)₁₀}₂{μ-η¹:η¹,μ-η¹:η¹-(C₈H₅N)–C–(C₅H₃N)}] 7, also forming an indolizine ring system. The structures of 1–3, 6, 6·2[CH₂Cl₂] and 7 have been established by X-ray crystallography.