Syntheses and molecular structures of 6-halogeno-pyridin-2-olate complexes with the diruthenium(2+) core

The complexes [Ru 2 (CO) 5 (μ-FpyO) 2 ] 2 ( 1 ), [Ru 2 (CO) 4 (μ-ClpyO) 2 ] 2 ( 2 ), and [Ru 2 (CO) 4 (μ-BrpyO) 2 ] 2 ( 3 ) were prepared from Ru 3 (CO) 12 and 6-fluoro-2-hydroxypyridine (FpyOH), 6-chloro-2-hydroxypyridine (ClpyOH) and 6-bromo-2-hydroxypyridine (BrpyOH), respectively, in hot toluene. Compounds 1 – 3 are coordination dimers with a cyclo -RuORuO motif. By carrying out the reaction in hot methanol, the dinuclear complexes [Ru 2 (CO) 4 (μ-ClpyO) 2 (CH 3 OH)] ( 4 ) and [Ru 2 (CO) 4 (μ-BrpyO) 2 (CH 3 OH)] ( 5 ), respectively, were obtained. Treatment of 2 and 3 with triphenylphosphane provided the complexes [Ru 2 (CO) 4 (μ-ClpyO) 2 (PPh 3 )] ( 6 ) and [Ru 2 (CO) 4 (μ-BrpyO) 2 (PPh 3 )] ( 7 ), respectively. The solid-state structures of complexes 1 , 2 , 4 , 6 , and 7 were determined by single crystal X-ray diffraction. In all cases, a head–head coordination of the two 6-halopyridinolate ligands at the Ru 2 2 + core was found. In all chlorine- or bromine-containing complexes, the axial coordination site at the ruthenium atom neighbored by two Cl or Br atoms remains unoccupied due to steric shielding by the halogen atom. In the fluoropyridinolate complex 1 , the same coordination site is occupied by a carbonyl ligand.