Ru₂(CO)₄{OOC(CH₂)<i>_n</i>CH₃}₂L₂ sawhorse-type complexes containing μ₂-η²-carboxylato ligands derived from saturated fatty acids

The thermal reaction of Ru₃(CO)₁₂ with the saturated fatty acids (heptanoic, nonanoic, decanoic, tridecanoic, tetradecanoic, heptadecanoic, octadecanoic) in refluxing tetrahydrofuran, followed by addition of triphenylphosphine (PPh₃) or pyridine (C₅H₅N), gives the dinuclear complexes Ru₂(CO)₄{OOC(CH₂)<i>_n</i>CH₃}₂L₂ (<b>1</b>: n = 5, <b>2</b>: n = 7, <b>3</b>: n = 8, <b>4</b>: n = 11, <b>5</b>: n = 12, <b>6</b>: n = 15, 7: n = 16; <b>a</b>: L = NC₅H₅, <b>b</b>: L = PPh₃). The single crystal structure analysis of <b>1b</b>, <b>2a</b>, <b>3a</b>, <b>4a</b> and <b>5a</b> reveals a dinuclear Ru₂(CO)₄ sawhorse structure, the diruthenium backbone being bridged by the carboxylato ligands, while the two L ligands occupy the axial positions at the ruthenium atoms. In <b>2a</b>, π-π stacking interactions between adjacent pyridyl units of symmetry related molecules prevail, while in the longer alkyl chain derivatives <b>3a</b>, <b>4a</b> and <b>5a</b>, additional van der Waals and electrostatic interactions between the alkyl chains take place as well in the packing arrangement of the molecules, thus giving rise to layers of parallel alkyl chains in the crystal.