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Synthesis, Reactivity, and Structure of Strictly Homologous 18 and 19 Valence Electron Iron Nitrosyl Complexes
Author(s) -
Sellmann Dieter,
Blum Nicole,
Heinemann Frank W.,
Hess Bernd A.
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010504)7:9<1874::aid-chem1874>3.0.co;2-2
Subject(s) - antibonding molecular orbital , unpaired electron , chemistry , crystallography , valence (chemistry) , valence electron , molecular orbital , density functional theory , pyridine , atom (system on chip) , reactivity (psychology) , ligand (biochemistry) , electron , computational chemistry , molecule , atomic orbital , medicinal chemistry , physics , organic chemistry , biochemistry , alternative medicine , receptor , pathology , quantum mechanics , computer science , embedded system , medicine
The 18 and 19 valence electron (VE) nitrosyl complexes [Fe(NO)(′pyS 4 ′)]BF 4 ([ 1 ]BF 4 ) and [Fe(NO)(′pyS 4 ′)] ( 2 ) have been synthesized from [Fe(′pyS 4 ′)] x (′pyS 4 ′ 2− =2,6‐bis(2‐mercaptophenylthiomethyl)pyridine(2−)) and either NOBF 4 or NO gas. Complex [ 1 ]BF 4 was also obtained from [Fe(CO)(′pyS 4 ′)] and NOBF 4 . The cation [ 1 ] + is reversibly reduced to give 2 . Oxidation of 2 by [Cp 2 Fe]PF 6 afforded [Fe(NO)(′pyS 4 ′)]PF 6 ([ 1 ]PF 6 ). The molecular structures of [ 1 ]PF 6 and 2 were determined by X‐ray crystallography. They demonstrate that addition of one electron to [ 1 ] + causes a significant elongation of the Fe‐donor atom bonds and a bending of the FeNO angle. Density functional calculations show that the unpaired electron in 2 occupies an orbital, which is antibonding with respect to all Fe‐ligand interactions. As expected from qualitative Molecular Orbital (MO) theory, it has a large contribution from a π* type NO orbital. The ν (NO) frequency decreases from 1893 cm −1 in [ 1 ]BF 4 to 1648 cm −1 in 2 (in KBr). The antibonding character of the unpaired electron explains the ready reaction of 2 with excess NO to give [Fe(NO) 2 (′pyS 4 ′)] ( 3 ), the facile NO/CO exchange of 2 to afford [Fe(CO)(′pyS 4 ′)], and the easy oxidation of 2 to [ 1 ] + .