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Studies on Chemical Reactivity and Electrocatalysis of Two Acylmethyl(hydroxymethyl)pyridine Ligand-Containing [Fe]-Hydrogenase Models (2-COCH2‑6-HOCH2C5H3N)Fe(CO)2L (L = η1‑SCOMe, η1‑2-SC5H4N)

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journal contribution
posted on 30.11.2017, 13:03 by Li-Cheng Song, Liang Zhu, Fu-Qiang Hu, Yong-Xiang Wang
On the basis of preparation and characterization of [Fe]-H2ase models (2-COCH2-6-HOCH2C5H3N)­Fe­(CO)2L (A, L = η1-SCOMe; B, L = η1-2-SC5H4N), the chemical reactivities of A and B with various electrophilic and nucleophilic reagents have been investigated, systematically. Thus, when A reacted with 1 equiv of MeCOCl in the presence of Et3N in MeCN to give the η2-SCOMe-coordinated acylation product (2-COCH2-6-MeCO2CH2C5H3N)­Fe­(CO)22-SCOMe) (1), treatment of A with excess HBF4·Et2O in MeCN gave the cationic MeCN-coordinated complex [(2-COCH2-6-HOCH2C5H3N)­Fe­(CO)2­(MeCN)]­(BF4) (2). In addition, when 2 was treated with 1 equiv of 2,6-(p-4-MeC6H4)2­C6H3SK or PPh3 in CH2Cl2 to give the thiophenolato- and PPh3-substituted derivatives (2-COCH2-6-HOCH2C5H3N)­Fe­(CO)2[2,6-(p-MeC6H4)2­C6H3S] (3) and [(2-COCH2-6-HOCH2­C5H3N)­Fe­(CO)2­(PPh3)]­(BF4) (4), treatment of B with 1 equiv of PMe3 or P­(OMe)3 in THF afforded the phosphine- and phosphite-substituted complexes (2-COCH2-6-HOCH2C5H3N)­(η1-2-SC5H4N)­Fe­(CO)2L (5, L = PMe3; 6, L = P­(OMe)3). Interestingly, in contrast to A, when B reacted with excess HBF4·Et2O in MeCN to afford the BF3 adduct [2-COCH2-6-HO­(BF3)­CH2C5H3N]­Fe­(CO)2­(η1-2-SC5H4N) (7), reaction of B with 1 equiv of p-MeC6H4COCl in the presence of Et3N in MeCN gave not only the expected 2-acylmethyl-6-p-toluoyloxomethylpyridine-containing complex (2-COCH2-6-p-MeC6H4CO2­CH2C5H3N)­Fe­(CO)22-2-SC5H4N) (8), but also gave the unexpected 2-toluoyloxovinyl-6-toluoyloxo­methylpyridine-containing complex (2-p-MeC6H4CO2C2H-6-p-MeC6H4CO2­CH2C5H3N)­Fe­(CO)22-2-SC5H4N) (9). While the possible pathways for the novel reactions leading to complexes 1, 2, and 79 are suggested, the structures of complexes B, 14, and 69 were unambiguously confirmed by X-ray crystallography. In addition, model complexes A and B have been found to be catalysts for proton reduction to H2 from TFA under CV conditions.