ic0702567_si_009.cif (10.44 kB)

Dinitrosyl Iron Complexes (DNICs) Containing S/N/O Ligation:  Transformation of Roussin's Red Ester into the Neutral {Fe(NO)2}10 DNICs

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posted on 11.06.2007, 00:00 by Ming-Li Tsai, Chung-Hung Hsieh, Wen-Feng Liaw
Addition of the Lewis base [OPh]- to the THF solution of Roussin's red ester [Fe(μ-SC6H4-o-NHCOPh)(NO)2]2 (1) and [Fe(μ-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 σ-donating and π-accepting PPh3 ligand triggered the reductive elimination of bridged thiolates of complex 1 to yield the neutral {Fe(NO)2}10, [(PPh3)2Fe(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(μ-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)2Fe(PPh3)2]. A straightforward reaction of complex 6 and 4 equiv of [N3]- conducted in THF led to the anionic {Fe(NO)2}9, [(N3)2Fe(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.