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

We have developed two novel synthetic
methods, by which two types
of mononuclear Fe model complexes for the active site of [Fe]­hydrogenase
are successfully synthesized. The first type of 2-acylmethyl-6-hydroxymethylpyridine-containing
complexes, [2-COCH2-6-HOCH2C5H3N]­Fe­(CO)2G (1, G = PhCO2; 2, PhCOS; 3, PhCS2; 4, 2-S-6-MeC5H3N), were prepared by
a “one-pot” method involving reaction of 2-TsO-6-HOCH2C5H3N (Ts = 4-MeC6H4SO2) with Na2Fe­(CO)4 followed by
treatment of the resulting Fe(0) intermediate [Na­(2-CH2-6-HOCH2C5H3N)­Fe­(CO)4] (M1) with (PhCO2)2, (PhCOS)2, (PhCS2)2, and (2-S-6-MeC5H3N)2 in 49–72% yields, respectively.
The second type of 2-acylmethyl-6-hydroxypyridine-containing complexes,
(2-COCH2-6-HOC5H3N)­Fe­(CO)2(2-SCO-6-RC5H3N) (9a, R = MeO; 9b, R = PhS), could be prepared via a multiple-step synthetic
method. This method involves (i) treatment of 2-ClCO-6-RC5H3N (R = MeO, PhS) with NaSH followed by acidification
with diluted HCl to give 2-HSCO-6-RC5H3N (5a, R = MeO; 5b, R = PhS); (ii) further treatment
of 5a,b with KOH to afford 2-KSCO-6-RC5H3N (6a, R = MeO; 6b,
R = PhS); (iii) treatment of 2-TsOCH2-6-PMBOC5H3N (PMB = 4-MeOC6H4CH2) with Na2Fe­(CO)4 followed by treatment of
the resulting Fe(0) intermediate [Na­(2-CH2-6-PMBOC5H3N)­Fe­(CO)4] (M2) with
Br2 or I2 to produce (2-COCH2-6-PMBOC5H3N)­Fe­(CO)3X (7a,
X = Br; 7b, X = I); (iv) further treatment of 7a,b with 6a,b to yield (2-COCH2-6-PMBOC5H3N)­Fe­(CO)2(2-S-6-RC5H3N) (8a, R = MeO; 8b, R = PhS); and (v) finally, removal of the PMB groups from 8a,b under the action of deprotecting reagent
CF3CO2H/EtSH to give complexes 9a,b. All compounds 1–4 and 5a,b–9a,b with the exception of 7b are new and have been
characterized by elemental analysis, spectroscopy, and, particularly
for 1, 4, and 7a–9a, X-ray crystallography.