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]

full title: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)23P(OMe)3(μ-I)2] and of two isomers of [Os10C(CO)21P(OMe)34] 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)23P(OMe)3(μ-I)2] (5) and [Os10C(CO)21P(OMe)34] (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)23P(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.