Functionalized nickel(II)-iron(II) dithiolates as biomimetic models of [NiFe]-Hases.

To develop the structural and functional modeling chemistry of [NiFe]-Hases, a series of new biomimetics for the active site of [NiFe]-Hases have been prepared by various synthetic methods. Treatment of the mononuclear Ni complex (pnp)NiCl (pnp = (PhPCH)NPh) with (dppv)Fe(CO)(pdt) (dppv = 1,2-(PhP)CH, pdt = 1,3-propanedithiolate) and KPF gave the dicarbonyl complex (pnp)Ni(pdt)Fe(CO)(dppv) (1). Further treatment of 1 and (dppe)Ni(pdt)Fe(CO)(dppv) (dppe = 1,2-(PhP)CH) with the decarbonylation agent MeNO and pyridine afforded the novel sp C-Fe bond-containing complexes [(pnp)Ni(SCHCHCHS)Fe(CO)(dppv)]PF ([2]PF) and [(dppe)Ni(SCHCHCHS)Fe(CO)(dppv)]BF ([3]BF). More interestingly, the first -carboxylato complexes [(pnp)Ni(pdt)Fe(CO)(-OCR)(dppv)]PF ([4]PF, R = H; [5]PF, R = Me; [6]PF, R = Ph) could be prepared by reactions of [1]PF with the corresponding carboxylic acids RCOH in the presence of MeNO, whereas further reactions of [4]PF-[6]PF with aqueous HPF and 1.5 MPa H gave rise to the μ-hydride complex [(pnp)Ni(pdt)Fe(CO)(μ-H)(dppv)]PF ([7]PF). Except for H activation by -carboxylato complexes [4]PF-[6]PF to give a μ-hydride complex ([7]PF), the sp C-Fe bond-containing complex [2]PF was found to be a catalyst for proton reduction to H under CV conditions. Furthermore, the chemical reactivity of the μ-hydride complex [7]PF displayed in the e transfer reaction with FcPF in the presence of CO, the H evolution reaction with the protonic acid HCl, and the H transfer reaction with -methylacridinium hexafluorophosphate ([NMA]PF) was systematically studied. As a result, a series of the expected products such as H, ferrocene, the dicarbonyl complex 1, the μ-chloro complex [(pnp)Ni(pdt)Fe(CO)(μ-Cl)(dppv)]PF ([8]PF), the -MeCN-coordinated complex (pnp)Ni(pdt)Fe(CO)(-MeCN)(dppv) (9) and the H transfer product AcrH were produced. While all the newly prepared model complexes were structurally characterized by spectroscopic methods, the molecular structures of some of their representatives were confirmed by X-ray crystallography.