The first acylmethyl(hydroxymethyl)pyridine ligand-containing [Fe]hydrogenase model complexes 2-4 have been synthesized starting from the nucleophilic substitution reaction of 2-(4-MeC(6)H(4)SO(3)CH(2))-6-HOCH(2)C(5)H(3)N with Na(2)Fe(CO)(4). While the reaction course for producing complex 3 via the highly unstable intermediate complex 1 is monitored by in situ IR spectroscopy, the isolated model complexes 2-4 are fully characterized.

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.

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-COCH 2 -6-HOCH 2 C 5 H 3 N]Fe(CO) 2 G (1, G = PhCO 2 ; 2, PhCOS; 3, PhCS 2 ; 4, 2-S-6-MeC 5 H 3 N), were prepared by a "one-pot" method involving reaction of 2-TsO-6-HOCH 2 C 5 H 3 N (Ts = 4-MeC 6 H 4 SO 2 ) with Na 2 Fe(CO) 4 followed by treatment of the resulting Fe(0) intermediate [Na(2-CH 2 -6-HOCH 2 C 5 H 3 N)Fe(CO) 4 ] (M1) with (PhCO 2 ) 2 , (PhCOS) 2 , (PhCS 2 ) 2 , and (2-S-6-MeC 5 H 3 N) 2 in 49−72% yields, respectively. The second type of 2-acylmethyl-6-hydroxypyridine-containing complexes, (2-COCH 2 -6-HOC 5 H 3 N)Fe(CO) 2 (2-SCO-6-RC 5 H 3 N) (9a, R = MeO; 9b, R = PhS), could be prepared via a multiple-step synthetic method. This method involves (i) treatment of 2-ClCO-6-RC 5 H 3 N (R = MeO, PhS) with NaSH followed by acidification with diluted HCl to give 2-HSCO-6-RC 5 H 3 N (5a, R = MeO; 5b, R = PhS); (ii) further treatment of 5a,b with KOH to afford 2-KSCO-6-RC 5 H 3 N (6a, R = MeO; 6b, R = PhS); (iii) treatment of 2-TsOCH 2 -6-PMBOC 5 H 3 N (PMB = 4-MeOC 6 H 4 CH 2 ) with Na 2 Fe(CO) 4 followed by treatment of the resulting Fe(0) intermediate [Na(2-CH 2 -6-PMBOC 5 H 3 N)Fe(CO) 4 ] (M2) with Br 2 or I 2 to produce (2-COCH 2 -6-PMBOC 5 H 3 N)Fe(CO) 3 X (7a, X = Br; 7b, X = I); (iv) further treatment of 7a,b with 6a,b to yield (2-COCH 2 -6-PMBOC 5 H 3 N)Fe(CO) 2 (2-S-6-RC 5 H 3 N) (8a, R = MeO; 8b, R = PhS); and (v) finally, removal of the PMB groups from 8a,b under the action of deprotecting reagent CF 3 CO 2 H/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.