Polyhedral rearrangements in undeca- and dodeca-nuclear Group 1B metal osmium clusters

Abstract

The series of heteronuclear clusters [Os₁₀C(CO)₂₄{M(PR₃)}₂][M = Au, PR₃= PMe₂Ph (2a); M = Ag, PR₃= PPh₃(2d)], [Os₁₀C(CO)₂₄{Au(PEt₃)}{Ag(PPh₃)}](2e), [Os₁₀C(CO)₂₄{Au(PMe₂Ph)}₃][ClO₄](3), and [Os₁₀C(CO)₂₄{M(PR₃)}]^–[M = Au, PR₃= PMe₂Ph (4a); M = Ag, PR₃= PPh₃(4d); M = Cu, PR₃= PPh₃(4e)] have been prepared and shown to undergo molecular rearrangement in solution; two isomeric forms of (2a), (2e), and (4a) have been identified and their interconversion is considered to involve a cap ⇆ edge bridge ⇆ cap (c.e.c.) pathway. The reactivity of [Os₁₀C(CO)₂₄{M(PR₃)}]^–(M = Cu, Ag, or Au) with isolobal moieties such as H⁺ and [Cu( NCMe)]⁺ has been explored, and found to yield the mixed metal clusters [Os₁₀C(CO)₂₄{M(PR₃)}{Cu(NCMe)}][M = Au, PR₃= PPh₃(5a), or PEt₃(5b); M = Ag, PR₃= PPh₃(5c)] and [Os₁₀(H)C(CO)₂₄{M(PPh₃)}][M = Au (6a), Ag (6b), or Cu (6c)]. The reaction of (6a) or (6b) with AgClO₄yields the known eicosaosmium cluster [Os₂₀M(C)₂(CO)₄₈]^2–[M = Au (7a) or Ag (7b)]. These dianionic clusters have been found to be readily reduced by sodium diphenylketyl, to yield the trianionic species [Os₂₀M(C)₂(CO)₄₈]^3–[M = Au (8a) or Ag (8b)].