Construction de complexes tétranucléaires de ruthénium à ossature planaire par condensation de deux unités diruthénium à l'aide de ligands pontants: Synthèse et structure moléculaire de [Ru 4 (CO) 8 {μ 2 ‐P(Cy) 2 } 4 ] et de [Ru 4 (CO) 8 {μ 4 ‐P(Cy)} 2 {μ 2 ‐P(Cy) 2 } 2 ] (Cy = cyclohexyl)

Assembly of Tetranuclear Ruthenium Complexes with Planar Metal Core by Condensation of Two Diruthenium Units Using Bridging Ligands: Synthesis and Molecular Structure of [Ru 4 (CO) 8 {μ 2 ‐P(Cy) 2 } 4 ] and [Ru 4 (CO) 8 {μ 4 ‐P(Cy)} 2 {μ 2 } 2 ](Cy = Cyclohexyl) The dinuclear complexes [Ru 2 (CO) 6 {μ‐P(Cy) 2 } 2 ] ( 1 ) or [Ru 2 (CO) 4 {μ‐(HCO 2 )} 2 {P(Cy) 2 H} 2 ] ( 2 ) react in THF solution at 160° to give the tetranuclear complexes [Ru 4 (CO) 8 {μ 2 ‐P(Cy) 2 } 4 ] ( 3 ) and [Ru 4 (CO) 8 {μ 4 ‐P(Cy)} 2 {μ 2 ‐P(Cy) 2 } 2 ] ( 4 ), as well as the trinuclear complex [Ru 3 (CO) 7 (μ 2 ‐H){μ 2 ‐P(Cy) 2 } 3 ] ( 5 ). If the reaction is performed at 200°, the bicapped tetranuclear species 4 is obtained in a higher yield, whereas 3 and 5 are formed in trace amounts only. The phenyl derivatives [Ru 2 (CO) 6 {μ‐P(Ph) 2 } 2 ] ( 6 ) or [Ru 2 (CO) 4 {μ‐(EtCO 2 )} 2 {P(Ph) 2 H} 2 ] ( 7 ) react in a similar manner to give only the complex [Ru 4 (CO) 8 {μ 4 ‐P(Ph)} 2 {μ 2 ‐P(Ph) 2 } 2 ] ( 8 ), analogous to 4 . The molecular structure of 3 consists of a planar framework of four Ru‐atoms, each Ru—Ru bond being bridged by a μ 2 ‐dicyclohexylphosphino ligand. The complex 4 represents a planar rectangular Ru core, both faces being capped by μ 4 ‐cyclohexylphosphinidene ligands and two opposite edges being bridged by μ 2 ‐dicyclohexylphosphino ligands.