Studies on Chemical Reactivity and Electrocatalysis of Two Acylmethyl(hydroxymethyl)pyridine Ligand-Containing [Fe]-Hydrogenase Models (2-COCH-6-HOCHCHN)Fe(CO)L (L = η-SCOMe, η-2-SCHN).

On the basis of preparation and characterization of [Fe]-Hase models (2-COCH-6-HOCHCHN)Fe(CO)L (A, L = η-SCOMe; B, L = η-2-SCHN), 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 EtN in MeCN to give the η-SCOMe-coordinated acylation product (2-COCH-6-MeCOCHCHN)Fe(CO)(η-SCOMe) (1), treatment of A with excess HBF·EtO in MeCN gave the cationic MeCN-coordinated complex [(2-COCH-6-HOCHCHN)Fe(CO)(MeCN)](BF) (2). In addition, when 2 was treated with 1 equiv of 2,6-(p-4-MeCH)CHSK or PPh in CHCl to give the thiophenolato- and PPh-substituted derivatives (2-COCH-6-HOCHCHN)Fe(CO)[2,6-(p-MeCH)CHS] (3) and [(2-COCH-6-HOCHCHN)Fe(CO)(PPh)](BF) (4), treatment of B with 1 equiv of PMe or P(OMe) in THF afforded the phosphine- and phosphite-substituted complexes (2-COCH-6-HOCHCHN)(η-2-SCHN)Fe(CO)L (5, L = PMe; 6, L = P(OMe)). Interestingly, in contrast to A, when B reacted with excess HBF·EtO in MeCN to afford the BF adduct [2-COCH-6-HO(BF)CHCHN]Fe(CO)(η-2-SCHN) (7), reaction of B with 1 equiv of p-MeCHCOCl in the presence of EtN in MeCN gave not only the expected 2-acylmethyl-6-p-toluoyloxomethylpyridine-containing complex (2-COCH-6-p-MeCHCOCHCHN)Fe(CO)(η-2-SCHN) (8), but also gave the unexpected 2-toluoyloxovinyl-6-toluoyloxomethylpyridine-containing complex (2-p-MeCHCOCH-6-p-MeCHCOCHCHN)Fe(CO)(η-2-SCHN) (9). While the possible pathways for the novel reactions leading to complexes 1, 2, and 7-9 are suggested, the structures of complexes B, 1-4, and 6-9 were unambiguously confirmed by X-ray crystallography. In addition, model complexes A and B have been found to be catalysts for proton reduction to H from TFA under CV conditions.