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 PS2H 2 (PS2H 2 = 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 PPh 3 to the solution of dinuclear 1 leads to the formation of mononuclear {FeNO} 7 [Fe(NO)(PS2)(PPh 3 )] ( 2 ) that shows electrochemical responses similar to those of 1 . One-electron reduction of 1 with Cp* 2 Co or KC 8 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 Fe II /{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).