The synthesis and characterization of Re3(μ-H)3(CO)9 − n(PMe3)n(μ3-η2:η2:η2-C60) (n = 2, 3) complexes

Treatment of Re3(μ-H)3(CO)9(μ3-η2:η2:η2-C60) (1) with 2.2 equiv. of Me3NO in the presence of excess PMe3 in chlorobenzene (CB) gave the bisphosphine-substituted complex 1,2-Re3(μ-H)3(CO)7(PMe3)2(μ3-η2:η2:η2-C60) as two diastereomers, 2a (major, 38%) and 2b (minor, 11%). The corresponding reaction of 1 with 3.3 equiv. of Me3NO, produced the trisphosphine-substituted isomeric product 1,2,3-Re3(μ-H)3(CO)6(PMe3)3(μ3-η2:η2:η2-C60) as two diastereomers, 3a (major, 37%) and 3b (minor, 15%). Complexes 2a–3b have been characterized by spectroscopic methods and elemental analyses. Single crystal X-ray diffraction studies were carried out for 2a and 3b. The hydrides were confirmed by 1H NMR spectroscopic method and directly located only for 3a by X-ray diffraction. The molecular structure of 2a confirms a face-capping μ3-η2:η2:η2-C60 ligand with one axial and one equatorial PMe3 ligand on adjacent rhenium atoms, whereas that for 3b exhibits pseudo-Cs symmetry with an additional equatorial PMe3 on the third rhenium atom. Molecular structures for 2b and 3a are proposed by axial PMe3 ligand placement and subsequent equatorial PMe3 placement, based on earlier observations of facile ligand site-exchange in closely related systems and were verified by 1H NMR spectroscopic method.