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Improved catalytic activity of ruthenium–arene complexes in the reduction of NAD+
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Soldevila-Barreda, Joan J., Bruijnincx, Pieter C. A., Habtemariam, Abraha, Clarkson, Guy J., Deeth, Robert J. and Sadler, P. J. (2012) Improved catalytic activity of ruthenium–arene complexes in the reduction of NAD+. Organometallics, Vol.31 (No.16). pp. 5958-5967. doi:10.1021/om3006307
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WRAP_Sadler_496_Organometallics2012-31-5958-5967-joan- deposit.pdf - Accepted Version Download (1603Kb) | Preview |
Official URL: http://dx.doi.org/10.1021/om3006307
Abstract
A series of neutral Ru-II half-sandwich complexes of the type [(eta(6)-arene)Ru(N,N')Cl] where the arene is para-cymene (p-cym), hexamethylbenzene (hmb), biphenyl (bip), or benzene (bn) and N,N' is N-(2-aminoethyl) -4-(trifluoromethyl)benzenesulfonamide (TfEn), N-(2-aminoethyl)-4-toluenesulfonamide (TsEn), or N-(2-aminoethyl)-methylenesulfonamide (MsEn) were synthesized and characterized. X-ray crystal structures of [(p-cym)Ru(MsEn)Cl] (1), [(hmb)Ru(TsEn)Cl] (5), [(hmb)Ru(TfEn)Cl] (6), [(bip)Ru(MsEn)Cl] (7), and [(bip)Ru(TsEn)Cl] (8) have been determined. The complexes can regioselectively catalyze the transfer hydrogenation of NAD(+) to give 1,4-NADH in the presence of formate. The turnover frequencies (TOF) when the arene is varied decrease in the order bn > bip > p-cym > hmb for complexes with the same N,N' chelating ligand. The TOF decreased with variation in the N,N' chelating ligand in the order TfEn > TsEn > MsEn for a given arene. [(bn)Ru(TfEn)Cl] (12) was the most active, with a TOP of 10.4 h(-1). The effects of NAD(+) and formate concentration on the reaction rates were determined for [(p-cym)Ru(TsEn)Cl] (2). Isotope studies implicated the formation of [(arene)Ru(N,N')(H)] as the rate-limiting step. The coordination of formate and subsequent CO2 elimination to generate the hydride were modeled computationally by density functional theory (DFT). CO2 elimination occurs via a two-step process with the coordinated formate first twisting to present its hydrogen toward the metal center. The computed barriers for CO2 release for arene = benzene follow the order MsEn > TsEn > TfEn, and for the Ms En system the barrier followed bn < hmb, both consistent with the observed rates. The effect of methanol on transfer hydrogenation rates in aqueous solution was investigated. A study of pH dependence of the reaction in D2O gave the optimum pH* as 7.2 with a TOF of 1.58 h(-1) for 2. The series of compounds reported here show an improvement in the catalytic activity by an order of magnitude compared to the ethylenediamine analogues.
| Item Type: | Journal Article | ||||
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| Subjects: | Q Science > QD Chemistry Q Science > QP Physiology |
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| Divisions: | Faculty of Science > Chemistry | ||||
| Library of Congress Subject Headings (LCSH): | NAD (Coenzyme), Hydrogenation, Catalysis, Ruthenium compounds, Aromatic compounds, Complex compounds, Reduction (Chemistry) | ||||
| Journal or Publication Title: | Organometallics | ||||
| Publisher: | American Chemical Society | ||||
| ISSN: | 0276-7333 | ||||
| Official Date: | 27 August 2012 | ||||
| Dates: |
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| Volume: | Vol.31 | ||||
| Number: | No.16 | ||||
| Page Range: | pp. 5958-5967 | ||||
| DOI: | 10.1021/om3006307 | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Access rights to Published version: | Restricted or Subscription Access |
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