Stable Bimetallic Fe II /{Fe(NO) 2 } 9 Moiety Derived from Reductive Transformations of a Diferrous-dinitrosyl Species.

A dimeric dithiolate-bridged species, [Fe(NO)(PS2)]2 ( 1 ) containing two {FeNO}7 units, can be isolated by treating [Fe(CO)2 (NO)2 ] with PS2H2 (PS2H2 = bis(2-dimercaptophenyl)phenylphosphine). Crystallographic studies reveal the syn-configuration of NO units and the bridging thiolates in the butterfly shape of the 2Fe2S core. Addition of PPh3 to the solution of dinuclear 1 leads to the formation of mononuclear {FeNO}7 [Fe(NO)(PS2)(PPh3 )] ( 2 ) that shows electrochemical responses similar to those of 1 . One-electron reduction of 1 with Cp*2 Co or KC8 results in the isolation of thiolate-bridged bimetallic DNIC, [(PS2)Fe(μ-PS2)Fe(NO)2 ]- ([ 3 ]- ), confirmed by several spectroscopies including single-crystal X-ray diffraction studies. The bimetallic DNIC [ 3 ]- is a rare example obtained from the one-electron reduction of a dinuclear Fe-NO {FeNO}7 model complex. With the assistance of redox behaviors of 2 , electrochemical studies imply that the reduction of 1 leads to the formation of a mononuclear {FeNO}8 [Fe(NO)(PS2)(THF)]- intermediate, which involves disproportionation or NO- transfer to yield [ 3 ]- . Based on IR data and magnetic properties, the electronic structure of [ 3 ]- can be described as a FeII /{Fe(NO)2 }9 state. Isolation of the {Fe(NO)2 }9 moiety coordinated by the Fe ancillary complex lends strong support to the NO scrambling behavior in the effectiveness of the activity of flavodiiron nitric oxide reductases (FNORs).