SYNTHESIS, STRUCTURE, AND LIGAND DYNAMICS OF (MU-H)(MU-3-ETA-2-CH3C=NCH2CH3)RU3(CO)9

The reaction of triethylamine with Ru₃(CO)₁₂ in refluxing hexanes catalyzed by Fe₂(CO)₄(SEt)₂(PPh₃)₂ is shown to yield the complex (¼-H)Ru₃(CO)₉¼₃-n₂-CH₃C==NCH₂CH₃) as the major product (30%). An X-ray crystallographic investigation of I reveals that the organic ligand is parallel to one edge of the metal triangle and acts as a five-electron donor. The hydride was located; it symmetrically bridges the two metal atoms parallel to the C-N vector and is in the plane of the metal triangle. Compound I crystallizes in the PI space group with a = 8.396 (2) Å, b = 15.198 (3) Å, c = 8.093 (2) Å, a = 102.95 (2)°, ² = 108.63 (2)°, and y = 90.33 (2)°. Least-squares refinement based on 2867 observed reflections led to a final R value of 3.3% (Rv = 4.4%). The variable-temperature and ¹³C NMR spectra reveal that the organic ligand is fluxional, undergoing restricted oscillatory motion which is coupled to hydride edge hopping and axial- radial exchange on two of the three ruthenium atoms.