Inorganic Chemistry, Vol.46, No.12, 5110-5117, 2007
Dinitrosyl iron complexes (DNICs) containing S/N/O ligation: Transformation of Roussin's red ester into the neutral {Fe(NO)(2)}(10) DNICs
Addition of the Lewis base [OPh](-) to the THF solution of Roussin's red ester [Fe(mu-SC6H4-o-NHCOPh)(NO)(2)](2) (1) and [Fe(mu-SC6H4-o-COOH)(NO)(2)](2) (2), respectively, yielded the EPR-active, anionic {Fe(NO)(2)}(9), [(SC6H4-o-NCOPh)Fe(NO)(2)](-) (3) with the anionic [SC6H4-o-NCOPh](2-) ligand bound to the {Fe(NO)(2)} core in a bidentate manner (S,N-bonded) and [(SC6H4-o-COO)Fe(NO)(2)](-) (4) with the anionic [SC6H4-o-COO](2-) ligand bound to the {Fe(NO)(2)} core in a bidentate manner (S,O-bonded), characterized by IR, UV-vis, EPR, and single-crystal X-ray diffraction. In contrast to the bridged-thiolate cleavage yielding the neutral {Fe(NO)(2)}(9), [(SC6H4-o-NHCOPh)(Im)Fe(NO)(2)] (Im = imidazole), by addition of 2 equiv of imidazole to complex 1 observed in the previous study, the addition of the stronger sigma-donating and pi-accepting PPh3 ligand triggered the reductive elimination of bridged thiolates of complex 1 to yield the neutral {Fe(NO)(2)}(10), [(PPh3)(2)Fe(NO)(2)]. These results unambiguously illustrate one aspect of how the nucleophile L (L = imidazole, PPh3, [OPh](-)) functions to control the reaction pathways (bridged-thiolate cleavage, reductive elimination, and deprotonation) upon the reaction of complex 1 and the nucleophile L. The EPR-active, dimeric {Fe(NO)(2)}(9) dinitrosyl iron complex (DNIC) [Fe(mu-SC7H4SN)(NO)(2)](2) (6), with S and N atoms of the anionic [-SC7H4SN-](-) (2-benzothiozolyl thiolate) ligands bound to two separate {Fe(NO)(2)}(9) cores, was also synthesized from reaction of bis(2-benzothiozolyl) disulfide and [(NO)(2)Fe(PPh3)(2)]. A straightforward reaction of complex 6 and 4 equiv of [N-3](-) conducted in THF led to the anionic {Fe(NO)(2)}(9), [(N-3)(2)Fe(NO)(2)](-) (7). Conclusively, the EPR-active, {Fe(NO)(2)}(9) DNICs can be classified into the anionic {Fe(NO)(2)}(9) DNICs with S/N/O ligation, the neutral {Fe(NO)(2)}(9) DNIC with one thiolate and one neutral imidazole ligation, and the cationic {Fe(NO)(2)}(9) DNICs with the neutral N-/P-containing coordinated ligands.