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Full Paper
Ruthenium Hydride Complexes with Zwitterionic Quinonoid Ligands – Isomer Separation, Structural Properties, Electrochemistry, and Catalysis
Article first published online: 13 DEC 2011
DOI: 10.1002/ejic.201101091
Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Issue
European Journal of Inorganic Chemistry
Special Issue: Coopertive & Redox Non-Innocent Ligands in Directing Organometallic Reactivity (Cluster Issue)
Volume 2012, Issue 3, pages 546–553, January 2012
Additional Information
How to Cite
Hohloch, S., Braunstein, P. and Sarkar, B. (2012), Ruthenium Hydride Complexes with Zwitterionic Quinonoid Ligands – Isomer Separation, Structural Properties, Electrochemistry, and Catalysis. Eur. J. Inorg. Chem., 2012: 546–553. doi: 10.1002/ejic.201101091
Publication History
- Issue published online: 16 JAN 2012
- Article first published online: 13 DEC 2011
- Manuscript Received: 10 OCT 2011
Funded by
- Baden-Württemberg Stiftung
- Fonds der Chemischen Industrie
- Deutsche Forschungsgemeinschaft
Keywords:
- Quinones;
- Ruthenium;
- Hydrides;
- Noninnocent ligands;
- Redox chemistry;
- Transfer hydrogenation catalysis
Abstract
Reactions of [Ru(PPh3)3(CO)(H)Cl] with the zwitterionic p-benzoquinonemonoimine-type ligands 4-(n-butylamino)-6-(n-butylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q1), 4-(isopropylamino)-6-(isopropylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q2), and 4-(benzylamino)-6-(benzylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q3) in the presence of a base led to the formation of mononuclear complexes [Ru(PPh3)2(CO)(H)(Q1–H)] (1a and 1b), [Ru(PPh3)2(CO)(H)(Q2–H)] (2a and 2b), and [Ru(PPh3)2(CO)(H)(Q3–H)] (3a and 3b), respectively. The positional isomers (a and b) that were formed in each case were separated by preparative TLC. The structural characterization of 2a and 3a·MeCN helped to identify the isomers, and established the distorted octahedral coordination geometry around the ruthenium center. The bond lengths in the complexes are consistent with localization of the double bonds in Q2–H and Q3–H in both their monodeprotonated and metal-coordinated forms. The Ru–C–O(carbonyl) bond angle is almost linear. Cyclic voltammetry of the complexes showed one oxidation and one reduction process. These are predominantly centered on the quinonoid ligands, which shows their redox-noninnocent character. Studies of transfer hydrogenation with 2a as a precatalyst showed that, in the presence of KOH, acetophenone could be converted to 1-phenylethanol within 10 h in over 90 % yield.