A Novel Acylmethylpyridinol Ligand Containing Dinuclear Iron Complex Closely Related to [Fe]-Hydrogenase

Abstract

On synthesizing the PMB-protected mononuclear iron complexes [2-C(O)CH 2 -6-PMBOC 5 H 3 N]Fe(CO) 3 I (6) and [2-C(O)CH 2 -6-PMBOC 5 H 3 N]Fe-(CO) 2 (2-SC 5 H 4 N) (7), the novel acylmethylpyridinol ligand containing dinuclear iron complex [2-C(O)CH 2 -6-HOC 5 H 3 N]Fe 2 (CO) 4 [2′-C(O)CH 2 -6′-OC 5 H 3 N](2-SC 5 H 4 N) ( 9), which is closely related to the active site of [Fe]-hydrogenase, has been prepared unexpectedly via removal of the PMB protecting group from 7 under the action of excess trifluoroacetic acid. The [Fe]-hydrogenase-related complex 9 and its precursor complexes 6 and 7 have been fully characterized by elemental analysis, spectroscopy, and X-ray crystallography.

Several New [Fe]Hydrogenase Model Complexes with a Single Fe Center Ligated to an Acylmethyl(hydroxymethyl)pyridine or Acylmethyl(hydroxy)pyridine Ligand

“…As shown in Scheme 5, the PMB-protected 27 with Br 2 and I 2 in 34% and 45% yields, respectively. The five-membered FeSC 2 N ferracycle-containing complexes 8a,b were further obtained by reaction of 7a with 6a or 7b with 6b in 73% and 92% yields, respectively.…”

“…27 It is believed that the unexpected production of E is most likely due to the high instability of the four-membered FeSCN ferracycle in complex D relative to the corresponding FeSC 2 N five-membered ferracycle in complexes 9a,b. Therefore, the four-membered FeSCN ferracycle in one molecule of D could be opened by nucleophilic attack at its Fe center by the hydroxy group oxygen atom of another molecule of D and then via the intramolecular coordination of the 27 The targeted model complexes 9a,b have been characterized by elemental analysis, IR, 1 H NMR, and 13 C{ 1 H} NMR spectroscopy. The IR spectra of 9a,b displayed two absorption bands in the range 2027−1966 cm −1 for their terminal CO ligands and one absorption band at 1654 and 1625 cm −1 for their acyl groups, which are very close to those of both previously reported terminal CO-and acylmethylpyridinecontaining model complexes.…”

“…The IR spectra of 9a,b displayed two absorption bands in the range 2027−1966 cm −1 for their terminal CO ligands and one absorption band at 1654 and 1625 cm −1 for their acyl groups, which are very close to those of both previously reported terminal CO-and acylmethylpyridinecontaining model complexes. 21,24,27 The 1 H NMR spectra of 9a,b showed two doublets at 3.83 and 4.30 or 3.92 and 4.35 ppm for the two diastereotopic H atoms in their acylmethyl groups, whereas the 13 C{ 1 H} NMR spectra displayed one signal at 267.4 or 264.5 ppm for their acyl C atoms, respectively. These NMR data are also very close to those of both terminal CO-and acylmethylpyridine-containing model complexes.…”

Novel reactions of homodinuclear Ni2complexes [Ni(RNPyS4)]2with Fe3(CO)12to give heterotrinuclear NiFe2and mononuclear Fe complexes relevant to [NiFe]- and [Fe]-hydrogenases

“…12,19,20 Guided by the well-elucidated active site structures of [NiFe]-and [Fe]-hydrogenases, synthetic chemists have designed and synthesized many transition-metal complexes as models for the active sites of [NiFe]-hydrogenases and [Fe]-hydrogenase. 20,[43][44][45][46][47][48][49][50][51][52][53] Recently, we launched a study on reactions of Fe 3 (CO) 12 with the [RN Py S 4 ]-type ligand-containing homodinuclear Ni 2 complexes [Ni(RN Py S 4 )] 2 (RN Py S 4 = 2,6-bis-(mercaptophenylthiomethyl)-4-R-pyridine; R = H, 54 MeO, Cl, Br, i-Pr), aimed to prepare a new type of [Ni(RN Py S 4 )] unit-containing [NiFe]-hydrogenase model complexes. This is because such model complexes are expected to be more stable than those [NiS 4 ] unit-containing model complexes 30,33 due to one additional coordination of the pyridine N atoms to their Ni atoms.…”

Reactions of dinuclear Ni2complexes [Ni(RNPyS4)]2(RNPyS4= 2,6-bis(2-mercaptophenylthiomethyl)-4-R-pyridine) with Fe(CO)3(BDA) (BDA = benzylidene acetone) leading to heterodinuclear NiFe and mononuclear Fe complexes related to the active sites of [NiFe]- and [Fe]-hydrogenases

“…[11][12][13] Since the active site structures of [NiFe]-and [Fe]-hydrogenases were successfully determined by X-ray crystallography, synthetic chemists have designed and synthesized many transition-metal complexes as models for the active sites of [NiFe]-hydrogenases and [Fe]-hydrogenase. [41][42][43][44][45][46][47][48][49][50][51][52] Recently, we reported a novel type of reactions of the [RN Py S 4 ] ligand-containing homodinuclear complexes [Ni(RN Py S 4 )] 2 (RN Py S 4 ¼ 2,6-bis(2-mercaptophenylthiomethyl)-4-R-pyridine, R ¼ H, MeO, Cl, Br, i-Pr) with homotrinuclear carbonyl complex Fe 3 (CO) 12 ; as a result, the reactions gave not only the [RN Py S 4 ] ligand-containing heterotrinuclear [NiFe]-hydrogenase model complexes NiFe 2 (RN Py S 4 )(CO) 5 , but also mononuclear [Fe]-hydrogenase model complexes Fe(RN Py S 4 )(CO). 53 To examine the inuence of the other iron carbonyl complex upon this type of reactions and to prepare the more natural heterodinuclear [Fe]-hydrogenase model complexes Fe(RN Py S 4 )CO 3 have been prepared by the studied reactions.…”