Diiron Azamonothiolates via Scission of Dithiadiazacyclooctanes by Iron Carbonyls

Abstract

The reaction of Fe₃(CO)₁₂ with the dithiadiazacyclooctanes [SCH₂N(R)CH₂]₂ affords Fe₂[SCH₂N(Me)CH₂](CO)₆ (R = Me, Bn). The methyl derivative 1^Me was characterized crystallographically (Fe-Fe = 2.5702(5) Å). Its low symmetry is verified by variable temperature ¹³C NMR spectroscopy which revealed that the turnstile rotation of the S(CH₂)Fe(CO)₃ and S(NMe)Fe(CO)₃ centers are subject to very different energy barriers. Although 1^Me resists protonation, it readily undergoes substitution by tertiary phosphines, first at the S(CH₂)Fe(CO)₃ center, as verified crystallographically for Fe₂[SCH₂N(Me)CH₂](CO)₅(PPh₃). Substitution by the chelating diphosphine dppe (Ph₂PCH₂CH₂PPh₂) gave Fe₂[SCH₂N(Me)CH₂](CO)₄(dppe), resulting from substitution at both the S(CH₂)Fe(CO)₃ and S(NMe)Fe(CO)₃ sites.