309965-01-3Relevant academic research and scientific papers
Successive O-H and sp3 C-H bond activation of ortho-substituted phenols by a ruthenium(0) complex
Hirano, Masafumi,Kurata, Naoki,Komiya, Sanshiro
, p. 18 - 26 (2008/10/08)
Successive O-H and sp3 C-H bond activation of ortho-substituted phenols has been achieved by the reactions of Ru(1,5-cyclooctadiene)(1,3,5-cyclooctatriene) (1) with 2,6-xylenol and 2-allylphenol in the presence of PMe3 giving oxaruthenacycle complexes such as cis-Ru[OC6H3(2-CH2)(6-Me)](PMe 3)4 (4) or Ru[OC6H4(2-η3-C3H 4)](PMe3)3 (5), respectively. They are formed by the initial protonation of Ru(1-2-η2:5-6-η 2-cycloocta-1,5-diene)(1-4-η 4-cycloocta-1,3,5-triene)(PMe3) by phenols giving cationic (η5-cyclooctadienyl)ruthenium(II) complexes [Ru(η5-C8H11)(PMe3) 3]+[OAr]-·(HOAr)n [Ar = C6H3Me2-2,6 (2a), C6H4(2-CH2CH=CH2) (2b), C6H4{2-(E)-CH-CHMe} (2c), Ph (2d); C6H4Me-2 (2e); C6H4(2-CHMe2) (2f), and C6H4(2-CMe3) (2g)] followed by sp3 C-H bond cleavage reaction. The molecular structure of 2c reveals that the cyclooctadienyl group coordinates to the ruthenium center by an η5-fashion, where one equivalent of (E)-2-propenylphenol is associated with aryloxo anion. Further treatment of 2a and 2c with PMe3 results in the formation of oxaruthenacycle complexes to give 4 and 5, respectively. These facts clearly demonstrate that this sp3 C-H bond cleavage reaction occurs at a divalent ruthenium center. On the other hand, reactions of 2d-g afford (hydrido)(aryloxo)ruthenium(II) complexes, cis-Ru(H)(OAr)(PMe3)4 [Ar = Ph (6a), C6H4Me-2 (6b), C6H4(2-CHMe2) (6c), C6H4(2-CMe3) (6d)].
