Reactions and properties of the dinuclear molybdenum complex [(η5-C5H3)2(CMe2)(SiMe2)]Mo2(CO)6

Reactions of the title complex (1), which features the rigid doubly-bridged biscyclopentadienyl ligand and the unusually long Mo–Mo bond in the structure, with a variety of classic substrates are explored. Complex 1 reacts with I2 in CH2Cl2 to give the expected Mo–Mo cleaved product [(η5-C5H3)2(CMe2)(SiMe2)]Mo2(CO)6I2 (2A) with a Mo–Mo distance of 5.329 Å. While the same reaction in benzene forms the product 2B, which has the same structural formula as 2A but a different conformation, in which the Mo–Mo distance is 6.442 Å. Reaction of 1 with Ph2E2 (E = S, Se) in refluxing toluene or under UV irradiation yields products with the carbonyls completely removed, [(η5-C5H3)2(CMe2)(SiMe2)]Mo2(EPh)2(μ-EPh)2 (3a–b). Reaction of 1 with [Et2NC(S)S]2 results in the di-substituted product [(η5-C5H3)2(CMe2)(SiMe2)]Mo2(CO)4(Et2NC(S)S)2 (4). Reaction of 1 with C2Ph2 affords the acetylene-bridged derivative [(η5-C5H3)2(CMe2)(SiMe2)]Mo2(CO)4(μ-C2Ph2) (5). Reaction of 1 with an excess of PPh3 in refluxing toluene only provides the mono-substituted derivative [(η5-C5H3)2(CMe2)(SiMe2)]Mo2(CO)5(PPh3) (6), while the reaction of 1 with excess P(OPh)3 under the same conditions produces not only the mono-substituted derivative [(η5-C5H3)2(CMe2)(SiMe2)]Mo2(CO)5(P(OPh)3) (7), but also the di-substituted derivative [(η5-C5H3)2(CMe2)(SiMe2)]Mo2(CO)4(P(OPh)3)2 (8). The reactivity and properties of the doubly-bridged molybdenum complex 1 and the corresponding non-bridged and singly-bridged analogs are compared. The molecular structures of 2A, 2B, 3a, 5 and 8 have been determined by single crystal X-ray diffraction.

Graphical abstractThermal or photochemical reactions of the title compound with a series of classic substrates, including I2, Ph2E2, [Et2NC(S)S]2, C2Ph2 and PR3, are reported. Among all the results obtained, two are especially noteworthy. The first is that the di-iodo complexes 2A and 2B have the same structural formula ([(η5-C5H3)2(CMe2)(SiMe2)]Mo2(CO)6I2) but different conformations. The second is that the detailed structure for a [Cp′Mo(SPh)2]2 type compound, [(η5-C5H3)2(CMe2)(SiMe2)]Mo2(EPh)2(μ-EPh)2 (3a), has been determined for the first time.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Complexes 2A and 2B have the same structural formula ([(η5-C5H3)2(CMe2)(SiMe2)]Mo2(CO)6I2) but different conformations. ► The structurally novel product (CMe2)(SiMe2)[(η5-C5H3)Mo(SPh)]2(μ-SPh)2 was obtained. ► The reactivity of title compound with non- and singly-bridged analogs was compared. ► The molecular structures of five compounds were determined by X-ray diffraction.