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

Abstract

The water-soluble ruthenium(II) mononuclear complexes [CpRu(CO) 2 NH 2 R]BF 4 (Cp = η 5 -C 5 H 5 ; R = C 6 H 11 (1), C 6 H 5 (2), CH 2 C 6 H 5 (3), CH(CH 3 )C 6 H 5 (4), CH 2 (C 6 H 4 O)CH 3 (5), CH 2 (C 6 H 4 )CN ( 6), C 6 H 2 (CH 3 ) 3 (7), CH 2 CHCH 2 (8), CH(CH 3 ) 2 ( 9)) were synthesized from the reaction of the organometallic Lewis acid [CpRu(CO) 2 ]BF 4 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, 1 H and 13 C NMR spectroscopy, and elemental analysis. Spectral data show that the amines are σ-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 NH 2 CH 3 ]BF 4 ( 10) and the dinuclear complex [CpRu-(CO) 2 NH 2 (CH 2 ) 6 NH 2 (CO) 2-RuCp][BF 4 ] 2 (11) demonstrated excellent catalytic activity in the oxidation of styrene using NaIO 4 as the co-oxidant with over 95% conversion and benzaldehyde yields, respectively, in some cases.

Crystal structure of (η 6-benzene)-(N-(2,6-dimethylphenyl)-1-(pyridin-2-yl)methanimine-κ2 N,N′)ruthenium(II) perchlorate monohydrate, C20H20Cl2N2O5Ru

“…The N-Ru-N bond angle is 76.90(5)°. The N-Ru-Cl bond angles range was 82.05(3)-88.41(3)°like in related compounds [7][8][9][10]. The water and the perchlorate anion are both involved in O-H· · · O hydrogen bonds.…”

Crystal structure of chlorido-(N-(2,5-dichlorophenyl)-1-(pyridin-2-yl)methanimine-κ2 N,N′)(η 6-1-isopropyl-4-methyl benzene) ruthenium (II) tetrafluoroborate, C22H22Cl3N2BF4Ru

“…They stabilize and protect the metal centre and thereby prevent rapid oxidation of the Ru(II) to Ru(III) [4]. The title compound is part of our continuing studies of half-sandwich ruthenium(II) complexes [5][6][7][8], in which the cationic species of the complex feature the known "pseudooctahedral three-legged piano stool" structure. As expected, the ruthenium centre is coordinated to the N,N′-bidentate ligand through the nitrogen atoms and the chlorido ligand and the three atoms serve as the base of the piano stool.…”

Selective Oxidation of Styrene on Nanostructured Cerium Vanadate Catalyst

“…16 Therefore, converting styrene into any value-added material is highly advantageous. In the past, numerous works reported for the oxidation of styrene with a ligand-based catalyst, 17 a nonmetallic catalyst, 18 a metallic catalyst, 19 and molecular sieves. 20 Cancino et al demonstrated a Cu-based homogeneous catalyst with 61% styrene conversion and 26% benzaldehyde selectivity.…”