Synthesis of di-, tri-, tetra- and pentacyclic arene complexes of ruthenium(II):[Ru(η6-polycyclic arene)-(1-5-η5-cyclooctadienyl)]PF6 and their reactions with NaBH4
The phenanthrene complex of ruthenium(II), [Ru(eta(6)-phenanthrene)(1,5-eta(5)-cyclooctadienyl)]PF6 (2c), is prepared by the reaction of Ru(eta(4)-1,5-COD)(eta(6)-1,3,5-COT) (1) with phenanthrene and HPF6 in 65% yield. Similar treatments with di- tri-, tetra- and pentacyclic arenes give corresponding polycyclic arene complexes, [Ru(eta(6)-polycyclic arene)(1-5-eta(5)-cyclooctadienyl)]PF6 [polycyclic arene = naphthalene (2b), anthracene (2d), triphenylene (2e), pyrene (2f) and perylene (2g)] in 46-90% yields. The molecular structure of the perylene complex 2g is characterized by X-ray crystallography. Reaction of 2c with NaBH4 gives a mixture of the 1,5- and 1,4-COD complexes of ruthenium(0), Ru(eta(6)-phenanthrene)(eta(4)-1,5-COD) (3c) and Ru(eta(6)-phenanthrene)(eta(4)-1,4-COD) (4c) in 76% in 1:8 molar ratio. The arene exchange reactions among cationic complexes [Ru(eta(6)-arene)(1-5-eta(5)-cyclooctadienyl)]PF6 (2) showed the coordination ability of arenes in the following order: benzene similar to triphenylene > phenanthrene > naphthalene > perylene similar to pyrene > anthracene, suggesting the benzo fused rings, particularly those of acenes, decreasing thermal stability of the arene complex. (c) 2007 Elsevier B.V. All rights reserved.