Synthesis and characterization of bis(pentadienyl)ruthenium compounds

Article abstract of DOI:10.1021/om50003a026

The syntheses of bis(2,4-dimethylpentadienyl)ruthenium and bis(2,3,4-trimethylpentadienyl)ruthenium are reported. Characterization was achieved by using infrared, ¹H NMR, ¹³C NMR, and mass spectroscopy, as well as elemental analysis. In both cases, variable-temperature ¹H NMR data reveals an unsymmetric ground state with respective barriers to ligand oscillation of 9.73 and 10.16 kcal/mol. A single-crystal X-ray diffraction study of Ru(2,3,4-C₈H₁₃)₂ has also been undertaken. The space group is C_i¹-P1 (No. 2) with a = 9.213 (4) A, b = 11.486 (4) ?, c = 7.811 (4) ?, α = 101.20 (4)°, β = 114.97 (3)°, γ = 91.89 (3)°, Z = 2, and D_calcd = 1.46 g/cm³. The final R factor was 0.059 for the 2158 independent observed reflections. Despite the fact that two nearly eclipsing CH₃?CH₃ interactions result, the complex still adopts the gauche-eclipsed conformation in preference to the anti conformation. The complex is characterized by average Ru-C and C-C bond distances of 2.188 (3) and 1.428 (5) ?, respectively. A number of comparisons are made between these structural data and that of ruthenocene as well as other metal pentadienyl and bis(cyclo-η⁵-dienyl)metal complexes.