Reactivity of Thiolate and Hydrosulfide with a Mononuclear {FeNO} 7 Complex Featuring a Very High N-O Stretching Frequency.

Synthesis, characterization, electronic structure, and redox reactions of a mononuclear {FeNO} 7 complex with a very high N-O stretching frequency in solution are presented. Nitrosylation of [(L KP )Fe(DMF)] 2+ ( 1 ) (L KP = tris((1-methyl-4,5-diphenyl-1H-imidazol-2-yl)methyl)amine) produced a five-coordinate {FeNO} 7 complex, [(L KP )Fe(NO)] 2+ ( 2 ). While complex 2 could accommodate an additional water molecule to generate a six-coordinate {FeNO} 7 complex, [(L KP )Fe(NO)(H 2 O)] 2+ ( 3 ), the coordinated H 2 O in 3 dissociates to generate 2 in solution. The molecular structure of 2 features a nearly linear Fe-N-O unit with an Fe-N distance of 1.744(4) Å, N-O distance of 1.162(5) Å, and <Fe-N-O angle of 178.3°, while that of 3 features a slightly bent Fe-N-O unit with an Fe-N distance of 1.750(5) Å, N-O distance of 1.157(6) Å, and <Fe-N-O angle of 173.3°. Complex 2 displays a very high N-O stretching frequency of 1844 cm - 1 in dichloromethane and readily dissociates NO when dissolved in coordinating solvents such as acetonitrile or N , N -dimethylformamide. Investigation of the reduction of 2 by FTIR-SEC and EPR spectroscopy shows the generation of a {Fe(NO) 2 } 9 species, and the results have been corroborated by electronic structure calculations. Furthermore, the reaction of 2 with bezenethiolate (PhS - ) and hydrosulfide (HS - ) allowed the unambiguous characterization of a dinitrosyl iron complex (DNIC), [Fe(SPh) 2 (NO) 2 ] 1 - , and an unprecedented complex, [{(L KP )Fe(DMF)} 2 {Fe 6 S 6 (NO) 6 }] 2+ , featuring an iron-sulfur prismane dianion.