Phosphine-modified thioester derivatives are shown to serve as efficient precursors to phosphine-stabilized ferrous acyl thiolato carbonyls, which replicate key structural features of the active site of the hydrogenase Hmd. The reaction of Ph2PC6H4C(O)SPh and sources of Fe(0) generates both Fe(SPh)(Ph2PC6H4CO)(CO) 3 (1) and the diferrous diacyl Fe2(SPh) 2(CO)3(Ph2PC6H4CO) 2, which carbonylates to give 1. For the extremely bulky arylthioester Ph2PC6H4C(O)SC6H 3-2,6-(2,4,6-trimethylphenyl)2, oxidative addition is arrested and the Fe(0) adduct of the phosphine is obtained. Complex 1 reacts with cyanide to give Et4N[Fe(SPh)(Ph2PC6H 4CO)(CN)(CO)2] (Et4N). 13C and 31P NMR spectra indicate that substitution is stereospecific and cis to P. The IR spectrum of - in vCN and vCO regions very closely matches that for HmdCN. XANES and EXAFS measurements also indicate close structural and electronic similarity of Et 4N to the active site of wild-type Hmd. Complex 1 also stereospecifically forms a derivative with TsCH2NC, but the adduct is more labile than Et4N. Tricarbonyl 1 was found to reversibly protonate to give a thermally labile derivative, IR measurements of which indicate that the acyl and thiolate ligands are probably not protonated in Hmd.
ASJC Scopus subject areas
- Colloid and Surface Chemistry