The synthesis and characterization of Re 3(μ-H) 3(CO) 9 − n(PMe 3) n(μ 3-η 2:η 2:η 2-C 60) ( n = 2, 3) complexes

Abstract

Treatment of Re 3(μ-H) 3(CO) 9(μ 3-η 2:η 2:η 2-C 60) ( 1) with 2.2 equiv. of Me 3NO in the presence of excess PMe 3 in chlorobenzene (CB) gave the bisphosphine-substituted complex 1,2-Re 3(μ-H) 3(CO) 7(PMe 3) 2(μ 3-η 2:η 2:η 2-C 60) as two diastereomers, 2a (major, 38%) and 2b (minor, 11%). The corresponding reaction of 1 with 3.3 equiv. of Me 3NO, produced the trisphosphine-substituted isomeric product 1,2,3-Re 3(μ-H) 3(CO) 6(PMe 3) 3(μ 3-η 2:η 2:η 2-C 60) 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 μ 3-η 2:η 2:η 2-C 60 ligand with one axial and one equatorial PMe 3 ligand on adjacent rhenium atoms, whereas that for 3b exhibits pseudo- Cs symmetry with an additional equatorial PMe 3 on the third rhenium atom. Molecular structures for 2b and 3a are proposed by axial PMe 3 ligand placement and subsequent equatorial PMe 3 placement, based on earlier observations of facile ligand site-exchange in closely related systems and were verified by 1H NMR spectroscopic method.