Synthesis and Characterization of New (η5-Cyclopentadienyl)dicarbonylruthenium(II) Amine Complexes: Their Application as Homogeneous Catalysts in Styrene Oxidation

The water-soluble ruthenium(II) mononuclear complexes [CpRu(CO)(2)NH2R]BF4 (Cp = eta(5)-O5H5; R = C6H11 (1), C6H5 (2), CH2C6H5 (3), CH(CH3)C6H5 (4), CH2(C6H4O)CH3 (5), CH2(C6H4)CN (6), C6H2(CH3)(3) (7), CH2CHCH2 (8), CH(CH3)2 (9)) were synthesized from the reaction of the organometallic Lewis acid [CpRu(CO)(2)]BF4 with amine ligands at room temperature. These complexes are reported for the first time and have been fully characterized by IR, high-resolution mass spectrometry, H-1 and C-13 NMR spectroscopy, and elemental analysis. Spectral data show that the amines are sigma-bonded to the metal center via the nitrogen atom. The crystal structures of complexes 3 and 8 were determined by single-crystal X-ray crystallography. The 4-methoxybenzylamine, 4-aminomethylbenzonitrile and allylamine groups preferentially bind to the metal center via the amine nitrogen. The ruthenium complexes 1, 3-6, 9, and [CpRu(CO)(2)NH2CH3]BF4 (10) and the dinuclear complex [CpRu(CO)(2)NH2(CH2)(6)NH2(CO)(2-)RuCp][BF4](2) (11) demonstrated excellent catalytic activity in the oxidation of styrene using NaIO4 as the co-oxidant with over 95% conversion and benzaldehyde yields, respectively, in some cases.