Synthesis, structure, and reactions of a new dimer of molybdenocene, and related bi- and tri-nuclear compounds; molecular structures of [H(η5-C5H5)2Mo(µ-σ:η5-C5H4)Mo(η5-C5H5)], [(η5-C5H5)(OC)Mo(µ-η5:σ-C5H4)Mo(CO)2(η5-C5H5)], and [{Mo(η5-C5H5)}2(µ-η5-C5H4-η5-C5H4)H3]PF6

Abstract

Convenient syntheses of the black dimer [H(η⁵-C₅H₅)₂Mo(µ-σ:η⁵-C₅H₄)Mo(η⁵-C₅H₅)](2) and the compound [(η⁵-C₅H₅)(OC)Mo(µ-η⁵:σ-C₅H₅)Mo(CO)₂(η⁵-C₅H₅)](5) are described. Compound (2) is a precursor for a number of new and known binuclear molybdenocene derivatives, including cis- or trans-[{Mo(η⁵-C₅H₅)H}₂(µ-σ:η⁵-C₅H₄)₂], [{Mo(η⁵-C₅H₅)H}₂(µ-η⁵-C₅H₄-η⁵-C₅H₄)], [{Mo(η⁵-C₅H₅)}₂(µ-H)(µ-O)(µ-η⁵-C₅H₄-η⁵-C₅H₄)]PF₆, and [{Mo(η⁵-C₅H₅)}₂(µ-H)(µ-OH)(µ-η⁵-C₅H₄-η⁵-C₅H₄)][PF₆]₂. Due to the variety of structural isomers found in this series of dimers, (2) and (5) were characterised by X-ray diffraction methods. The crystal structure of the trihydride [{Mo(η⁵-C₅H₅)}₂(µ-η⁵-C₅H₄-η⁵-C₅H₄)H₃]PF₆(9) is also reported. Compound (2) is monoclinic, space group P2₁/c, with a= 13.674(7), b= 8.012(7), c= 15.37(1)Å, β= 108.69(6)°, and Z= 4. Refinement converged at R= 0.062, R′= 0.090 for 2 149 observed reflections [l > 3σ(l)]. The Mo–Mo distance is 3.189(1)Å. The carbonyl dimer (5) is monoclinic, space group P2₁/n, with a= 8.644(2), b= 15.336(2), c= 12.203(6)Å, β= 92.59(3)°, and Z= 4. The final R value was 0.033 (R′= 0.045) for 3 574 observed reflections. The Mo–Mo distance is 3.089(1)Å. Both (2) and (5) contain a cyclopentadienediyl bridge. Crystals of (9) are orthorhombic, space group Pbcn, with a= 13.030(1), b= 13.302(3), c= 11.446(2)Å, and Z= 4. Refinement with 1 284 observed reflections resulted in R= 0.034, R′= 0.037. A fulvalene ligand bridges the two Mo atoms, which are separated by 3.227(1)Å. The black dimer (2) reacts with aqueous hydrochloric acid to give [Mo(η⁵-C₅H₅)₂Cl₂], providing a convenient laboratory-scale synthesis of this useful compound. The compound [{MO(η⁵-C₅H₅)}₂(µ-O–MoO₃)(µ-η⁵-C₅H₄-η⁵-C₅H₄)]·2Me2SO, which contains a unique µ-O–MoO₃ group, is also described.