Diiron Azamonothiolates via Scission of Dithiadiazacyclooctanes by Iron Carbonyls.

The reaction of Fe3 (CO)12 with the dithiadiazacyclooctanes [SCH2 N(R)CH2 ]2 affords Fe2 [SCH2 N(Me)CH2 ](CO)6 (R = Me, Bn). The methyl derivative 1Me was characterized crystallographically (Fe-Fe = 2.5702(5) Å). Its low symmetry is verified by variable temperature13 C 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 1Me resists protonation, it readily undergoes substitution by tertiary phosphines, first at the S(CH2 )Fe(CO)3 center, as verified crystallographically for Fe2 [SCH2 N(Me)CH2 ](CO)5 (PPh3 ). Substitution by the chelating diphosphine dppe (Ph2 PCH2 CH2 PPh2 ) gave Fe2 [SCH2 N(Me)CH2 ](CO)4 (dppe), resulting from substitution at both the S(CH2 )Fe(CO)3 and S(NMe)Fe(CO)3 sites.