Synthesis and characterization of 2-oxacycloalkylideneruthenium(II) complexes: X-ray crystal structure of the 2-oxacycloheptylidene complex [Ru{ [formula omitted]H 2}(η 5-C 9H 7)(PPh 3) 2][PF 6]·CH 2Cl 2

Abstract

The oxacyclocarbene complexes [Ru{ COCH 2(CH 2) nC H 2}(η 5-C 9H 7)LL′][PF 6]·(L=L′=PPh 3, n=1 ( 2a), 2 ( 3a), 3 ( 5a); L=L′=PMe 2Ph, n=1 ( 2b), 2 ( 3b), 3 ( 5b); LL′=dppm, n=1 ( 2c), 2 ( 3c), 3 ( 5c); L=PPh 3, L′=PMe 3, n=1 ( 2d), 2 ( 3d), 3 ( 5d)) have been prepared by reaction of [RuCl(η 5-C 9H 7)LL′] with 3-butyn-1-ol, 4-pentyn-1-ol and 5-hexyn-1-ol in refluxing ethanol and in the presence of NaPF 6. The process involves alkyne to vinylidene tautomerization to give hydroxyalkylvinylidene intermediate complexes. The vinylidene complexes [Ru{CC(H)(CH 2) 3CH 2OH}(η 5-C 9H 7)LL′][PF 6] (L=L′=PPh 3 ( 4a), L=L′=PMe 2Ph ( 4b), L=PPh 3, L′=PMe 3 ( 4d)) have been isolated from the reaction of [RuCl(η 5-C 9H 7)LL′] with 5-hexyn-1-ol. The first structure for a 2-oxacycloheptylidene complex, 5a, has been determined by X-ray diffraction methods. The molecular structure shows the typical pseudooctahedral three-legged piano-stool geometry around the ruthenium atom, which is linked to the phosphorus atoms of the triphenylphosphine ligands and to the C α of the oxacyclic carbene ligand; the coordination around the ruthenium atom is completed by a η 5-bonded indenyl ligand with the benzo ring orientated nearly trans to the carbene group (CA=16.6(6)°). The RuC1 distance, 1.89(1) Å, is somewhat shorter than that found for other oxacyclic carbene ruthenium(II) complexes. The oxacycloheptylidene ring adopts a ‘pseudochair’ conformation for the seven member ring and shows an appreciable deviation from vertical orientation (DA=29.7(5)°).