Surprising Condensation Reactions of the Azadithiolate Cofactor

Azadithiolate, a cofactor found in all [FeFe]‐hydrogenases, is shown to undergo acid‐catalyzed rearrangement. Fe 2 [(SCH 2 ) 2 NH](CO) 6 self‐condenses to give Fe 6 [(SCH 2 ) 3 N] 2 (CO) 17 . The reaction, which is driven by loss of NH 4 + , illustrates the exchange of the amine group. X‐ray crystallography reveals that three Fe 2 (SR) 2 (CO) x butterfly subunits interconnected by the aminotrithiolate [N(CH 2 S) 3 ] 3− . Mechanistic studies reveal that Fe 2 [(SCH 2 ) 2 NR](CO) 6 participate in a range of amine exchange reactions, enabling new methodologies for modifying the adt cofactor. Ru 2 [(SCH 2 ) 2 NH](CO) 6 also rearranges, but proceeds further to give derivatives with Ru‐alkyl bonds Ru 6 [(SCH 2 ) 3 N][(SCH 2 ) 2 NCH 2 ]S(CO) 17 and [Ru 2 [(SCH 2 ) 2 NCH 2 ](CO) 5 ] 2 S.