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. 2020 Aug 28;10(53):32069-32077.
doi: 10.1039/d0ra04344c. eCollection 2020 Aug 26.

Heterodinuclear nickel(ii)-iron(ii) azadithiolates as structural and functional models for the active site of [NiFe]-hydrogenases

Li-Cheng Song  1   2 , Bei-Bei Liu  1 , Wen-Bo Liu  1 , Zheng-Lei Tan  1
Affiliations

Heterodinuclear nickel(ii)-iron(ii) azadithiolates as structural and functional models for the active site of [NiFe]-hydrogenases

Li-Cheng Song et al. RSC Adv. .

Abstract

To develop the biomimetic chemistry of [NiFe]-H2ases, the first azadithiolato-bridged NiFe model complexes [CpNi{(μ-SCH2)2NR}Fe(CO)(diphos)]BF4 (5, R = Ph, diphos = dppv; 6, 4-ClC6H4, dppv; 7, 4-MeC6H4, dppv; 8, CO2CH2Ph, dppe; 9, H, dppe) have been synthesized via well-designed synthetic routes. Thus, treatment of RN[CH2S(O)CMe]2 with t-BuONa followed by reaction of the resulting intermediates RN(CH2SNa)2 with (dppv)Fe(CO)2Cl2 or (dppe)Fe(CO)2Cl2 gave the N-substituted azadithiolato-chelated Fe complexes [RN(CH2S)2]Fe(CO)2(diphos) (1, R = Ph, diphos = dppv; 2, 4-ClC6H4, dppv; 3, 4-MeC6H4, dppv; 4, CO2CH2Ph, dppe). Further treatment of 1-4 with nickelocene in the presence of HBF4·Et2O afforded the corresponding N-substituted azadithiolato-bridged NiFe model complexes 5-8, while treatment of 8 with HBF4·Et2O resulted in formation of the parent azadithiolato-bridged model complex 9. While all the new complexes 1-9 were characterized by elemental analysis and spectroscopy, the molecular structures of model complexes 6-8 were confirmed by X-ray crystallographic study. In addition, model complexes 7 and 9 were found to be catalysts for H2 production with moderate i cat/i p and overpotential values from TFA under CV conditions.

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Conflict of interest statement

There are no conflicts of interest to declare.

Figures

Fig. 1
Fig. 1. Active site of [NiFe]-H2ases.
Fig. 2
Fig. 2. Models of [NiFe]-H2ases reported in this article.
Scheme 1
Scheme 1. Synthesis of precursor complexes 1–4.
Scheme 2
Scheme 2. Synthesis of targeted models 5–8.
Scheme 3
Scheme 3. Synthesis of targeted model 9.
Fig. 3
Fig. 3. Molecular structure of model complex 6 with ellipsoids drawn at a 50% probability level. All hydrogen atoms and the anion BF4− are omitted for clarity.
Fig. 4
Fig. 4. Molecular structure of model complex 7 with ellipsoids drawn at a 50% probability level. All hydrogen atoms and the anion BF4− are omitted for clarity.
Fig. 5
Fig. 5. Molecular structure of model complex 8 with ellipsoids drawn at a 50% probability level. All hydrogen atoms and the anion BF4− are omitted for clarity.
Fig. 6
Fig. 6. Cyclic voltammograms of 7 and 9 (1.0 mM) in 0.1 M n-Bu4NPF6/MeCN at a scan rate of 0.1 V s−1. Arrows indicate the starting potential and scan direction.
Fig. 7
Fig. 7. Cyclic voltammograms of 7 (1.0 mM) with TFA (0–10 mM) in 0.1 M n-Bu4NPF6/MeCN at a scan rate of 0.1 V s−1.
Fig. 8
Fig. 8. Cyclic voltammograms of 9 (1.0 mM) with TFA (0–10 mM) in 0.1 M n-Bu4NPF6/MeCN at a scan rate of 0.1 V s−1.
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