Synthesis, characterization, and crystal structures of N-functionalized diiron azadithiolate complexes related to the active site of [FeFe]-hydrogenases

A series of N-functionalized diiron azadithiolate complexes, [(µ-SCH2)2NCH2CO2Me]Fe2(CO)5 L [L = CO (1); PPh3 (2); Ph2PCH2PPh2 (3)], as active site models of [FeFe]-hydrogenases has been prepared and characterized. While 1 was prepared by a sequential reaction of (µ-HS)2Fe2(CO)6 with two equiv. of aqueous HCHO, followed by treatment of (µ-HOCH2S)2Fe2(CO)6 with one equiv. of H2NCH2CO2Me in 46% yield; 2 and 3 were prepared by a carbonyl substitution reaction of 1 with PPh3 or Ph2PCH2PPh2 in the presence of Me3NO · 2H2O in 90% and 85% yields, respectively. The crystal structures of 1 and 2 revealed that the substituent attached to the bridgehead nitrogen occupies an equatorial position and the PPh3 ligand resides in an axial position of the square pyramid of Fe2.