Reactions of some decaosmium clusters with electrophilic and nucleophilic reagents: X-ray structure analyses of [N(PPh3)2][Os10C(CO)24(µ-I)], [Os10C(CO)24(µ-I)2], [N(PPh3)2]2[Os10C(CO)22(NO)I], [Os10C(CO)23{P(OMe)3}(µ-I)2] and of two isomers of [Os10C(CO)21{P(OMe)3}4]

Abstract

The carbido-dianion [Os₁₀C(CO)₂₄]^2–(1) reacts with halogens X₂ to give firstly [Os₁₀C(CO)₂₄(µ-X)]^–, and then [Os₁₀C(CO)₂₄(µ-X)₂](X = Cl, Br, or I). The dianion (1) is regenerated on treatment of [Os₁₀C(CO)₂₄(µ-X)]^– or [Os₁₀C(CO)₂₄(µ-X)₂] with the nucleophiles X^–, OH^–, PR₃(R = OMe or C₆H₅), C₅H₅N, MeCN, or CO in polar solvents (tetrahydrofuran, methanol, acetone, or dichloromethane). Treatment of [Os₁₀C(CO)₂₄(µ-I)₂](3) with [N(PPh₃)₂][NO₂] in dichloromethane gives the nitrosyl dianion [Os₁₀C(CO)₂₂(NO)I]^2–(4). With an excess of P(OMe)₃ in xylene, complex (3) gives a mixture of products from which the phosphite-containing clusters [Os₁₀C(CO)₂₃{P(OMe)₃}(µ-I)₂](5) and [Os₁₀C(CO)₂₁{P(OMe)₃}₄](6) were separated and identified. The neutral species (5) was shown to react with an iodide ion, in a similar manner to the reaction shown by (3), to sequentially remove the bridging iodine ligands with formation of the dianion [Os₁₀C(CO)₂₃{P(OMe)₃}]^2–(5b). An isomer of the cluster (6), compound (6a), was prepared by the reaction of [Os₁₀H₂C(CO)₂₄] with P(OMe)₃ in xylene. Crystal-structure analyses of complexes [N(PPh₃)₂][Os₁₀C(CO)₂₄(µ-I)], (3), (4), (5), (6), and (6a) are reported and the possible mechanisms for their formation together with a discussion of the factors affecting the reactivity of the Os₁₀ series to nucleophiles are reported.