Hydrophilic quaternary ammonium-group-containing [FeFe]H2ase models prepared by quaternization of the pyridyl N atoms in pyridylazadiphosphine- and pyridylmethylazadiphosphine-bridged diiron complexes with various electrophiles. Issue 4 (10th January 2019)

• Record Type: Journal Article
• Authors: Song, Li-Cheng; Feng, Li; Guo, Yuan-Qiang
• Is Part Of: Dalton transactions. Volume 48:Issue 4(2018)
• Page Start: 1443
• Page End: 1453
• Publication Date: 2019-01-10
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c8dt04211j
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The first aromatic quaternary ammonium-group-containing [FeFe]H2 ase models have been prepared and some of them found to be catalysts for H2 production under CV conditions. Abstract : The first aromatic quaternary ammonium-group-containing [FeFe]H2 ase models have been prepared by a simple and convenient two-step method in high yields. Thus, on the basis of preparation of the N -pyridylazadiphosphine-bridged diiron complex (μ-PDT)Fe2 (CO)4 [μ-3-(Ph2 P)2 NC5 H4 N] (A ) by CO substitution of parent complex (μ-PDT)Fe2 (CO)6 with N -pyridylazadiphosphine 3-(Ph2 P)2 NC5 H4 N in refluxing xylene, further quaternization of the pyridyl N atom in complexA with electrophile 1, 3-propanesultone, 1, 3, 2-dioxathiolane-2, 2-dioxide, or 4-bromobutyric acid in refluxing MeCN afforded the pyridyl quaternary ammonium-group-containing models (μ-PDT)Fe2 (CO)4 [μ-3-(Ph2 P)2 NC5 H4 NR] (1, R = (CH2 )3 SO3 ;2, R = (CH2 )2 OSO3 ) and (μ-PDT)Fe2 (CO)4 [μ-3-(Ph2 P)2 NC5 H4 N(CH2 )3 CO2 H]Br (3 ). Similarly, the N -pyridylmethylazadiphosphine-bridged diiron complex (μ-PDT)Fe2 (CO)4 [μ-3-(Ph2 P)2 NCH2 C5 H4 N] (B ) could be prepared by CO substitution of parent complex (μ-PDT)Fe2 (CO)6 with N -pyridylmethylazadiphosphine 3-(Ph2 P)2 NCH2 C5 H4 N in refluxing xylene, while further quaternization of the pyridylmethyl N atom in complexB with 1, 3-propanesultone and 3-bromo-1-propanol in MeCN at reflux resulted in formation of the pyridylmethyl quaternary ammonium-group-containing models (μ-PDT)Fe2 (CO)4 [μ-3-(Ph2 P)2 NCH2 C5 H4 N(CH2 )3 SO3 ] (4 ) and (μ-PDT)Fe2 (CO)4 [μ-3-(Ph2 P)2 NCH2 C5 H4 N(CH2 )3 OH]Br (5 ), respectively. All new complexesA, B, and1–5 were characterized by elemental analysis and various spectroscopies, while the molecular structures of complexesA, B, 2 and5 were further confirmed by X-ray crystallography. The electrochemical study on hydrophilic models1 and3 in MeCN and the MeCN/H2 O mixed solvent indicated that the reduction potentials were shifted to less-negative potentials as the water content increased; such an observation implies that both1 and3 are easily reduced in the mixed MeCN/H2 O solvent than in MeCN. In addition, the electrocatalytic study demonstrated that both1 and3 can serve as electrocatalysts for H2 production from acetic acid with higher i cat / i p and TONs in MeCN/H2 O than in MeCN.