Iron-nitrosyl complex containing S-bonded monosulfinate [PPN][(NO)Fe(S,SO2-C6H4)(S,S-C6H4)] (3) has been isolated from sulfur oxygenation of complex [PPN][(NO)Fe(S,S-C6H4)2] (2) which is obtained from addition of NO molecule to [PPN][(C4H8O)Fe(S,S-C6H4)2] (1) in organic solvents. This result reveals that binding of NO to the iron center promotes sulfur oxygenation of iron dithiolates by dioxygen and stabilizes the S-bonded sulfinate iron species. Analysis of the bond angles for complexes 2 and 3 reveals that iron is best described as existing in a distorted trigonal bipyramidal coordination environment surrounded by one NO, three thiolates, and one sulfinate in complex 3, whereas the distorted square pyramidal geometry is adopted in complex 2. Complex 3 further reacts in organic solvents with molecular oxygen in the presence of [PPN][NO2] to produce the dinuclear bis(sulfinate) complex [PPN]2[(NO)Fe(SO2,SO2-C6H4)(S,S-C6H4)]2 (4). Complex 3 showed reaction with PPh3 in THF/CH2Cl2 to yield complex 2 and Ph3PO. Upon photolysis of CH2Cl2 solution of complex 3 under N2 purge at ambient temperature, the UV-vis and IR spectra consistent with the formation of complex 2 demonstrate that complex 2 and 3 are photochemically interconvertible. Obviously, complex 3 is thermally quite stable but is photochemically active toward [O] release. Also described are the X-ray crystal structures of 3 and 4.
The use of lateral substitution on the aromatic rings of the diacid component of diacid/bispyridyl AABB supramolecular LC polymers is effective at retarding crystallization presumably by introducing a 'carbuncle' along the chain which interferes with the requisite efficient close packing of molecular units. We have examined both one and two chloro groups per ring and have observed a glass transition and fiber formation in the least crystalline complex.
Mononuclear, distorted square planar [Ni(II)(ER)(P(o-C(6)H(4)S)(2)(o-C(6)H(4)SH))](-) (ER = SePh (1), 2-S-C(4)H(3)S (2)) with a S-H proton directly interacting with both nickel and sulfur atoms were prepared by reaction of [Ni(CO)(SePh)(3)](-)/[Ni(CO)(2-S-C(4)H(3)S)(3)](-) and P(o-C(6)H(4)SH)(3), individually. The presence of combinations of intramolecular [Ni-S...H-SR]/[Ni...H-SR] interactions was verified in the solid state by the observation of an IR nu(SH) stretching band (2273 and 2283 cm(-)(1) (KBr) for complexes 1 and 2, individually) and (1)H NMR spectra (delta 8.079 (d) (CD(2)Cl(2)) and 8.39 (d) (C(4)D(8)O) ppm (-SH) for complexes 1 and 2, respectively) and subsequently confirmed by X-ray diffraction study. The exo-thiol proton (o-C(6)H(4)SH) in complexes 1 and 2 was identified as a D(2)O exchangeable proton from NMR and IR studies and was quantitatively removed by Lewis base Et(3)N to yield Ni(II) dimer [Ni(II)(P(o-C(6)H(4)S)(3))](2)(2)(-) (5). Instead of the ligand-based oxidation to form dinuclear Ni(II) complexes and dichalcogenide, oxidation of THF-CH(3)CN solution of complexes 1 and 2 by O(2) resulted in the formation of the mononuclear, distorted trigonal bipyramidal [Ni(III)(ER)(P(o-C(6)H(4)S)(3))](-) (ER = SePh (3), 2-S-C(4)H(3)S (4)) accompanied by byproduct H(2)O identified by (1)H NMR, respectively. The 4.2 K EPR spectra of complexes 3 and 4 exhibiting high rhombicities with three principal g values of 2.304, 2.091, and 2.0 are consonant with Ni(III) with the odd electron in the d(z)(2) orbital. Complex 3 undergoes a reversible Ni(III/II) process at E(1/2) = -0.67 V vs Ag/AgCl in MeCN.
The pentacoordinate, 16-electron FeII complex [PPN][Fe(CO)2(CN)(S,NH-C6H4)] (1), stabilized by
strong S, N π-donation of chelating [S,NH-C6H4]2- ligand, was prepared by the reaction of 2-aminophenyl
disulfide and [PPN][Fe(CO)4(CN)]. Protonation of complex 1 by electrophiles (2-mercaptopyrimidine and
2-aminophenylthiol) yielded hexacoordinate iron(II)−thiolate cyanocarbonyl complexes [PPN][Fe(CO)(CN)(S-C4H3N2)2] (5) and [PPN][Fe(CO)2(CN)(S-C6H4NH2)(S,NH2-C6H4)] (3), respectively. The IR spectrum of
complex 5 in the aprotic solvent CH3CN displayed a weak ν(CN) band at 2090 cm-1 and a strong ν(CO) band
at 1945 cm-1. Chemical oxidation of complex 5 in CH3CN at − 20 °C with [Cp2Fe][PF6] displayed absorption
bands at 2096 and 1962 cm-1 which were assigned to the ν(CN) and ν(CO) vibrational frequencies respectively
of the thermally unstable neutral FeIII(CO)(CN)(S-C4H3N2)2. Complex 5 was reobtained upon addition of [PPN][BH4] to FeIII(CO)(CN)(S-C4H3N2)2 in CH3CN at −20 °C. The first dinuclear Fe(II)−thiolate cyanocarbonyl
compound [PPN]2[(CN)(CO)2Fe(μ-S,S-C6H4)]2 (4), the promising structural and functional model compound
of the dinuclear iron active sites of [Fe]-only hydrogenases isolated from D. desulfuricans and C.
pasteurianum,
was prepared by reacting 1,2-benzenedithiol with complex 1 in THF at −10 °C. The X-ray structural analysis
shows that complex 4 possesses crystallographically imposed centrosymmetry. Two six-coordinate Fe(II) centers
are connected via two thiolate bridges, and both CN- ligands point into the antiparallel direction. The IR
spectrum of complex 4 in the aprotic solvent CH2Cl2 revealed a weak absorption band for the CN- ligands at
2101 cm-1, and two strong absorption bands for the CO groups at 2013 and 1960 cm-1. When the CH2Cl2
solution of complex 4 was exposed to 13CO at 0 °C, absorbances at 1968 and 1915 cm-1 appeared within 10
min. Reappearance of the 2013 and 1960 cm-1 bands on the removal of the 13CO and replacement with 12CO
atmosphere demonstrated reversibility of the CO ligand lability of complex 4. The vibrational spectroscopies
of the Fe(CO)2(CN) and Fe(CO)(CN) fragments (ν(CN) ranges from 2094 to 2105 cm-1, ν(CO) ranges from
1928 to 2013 cm-1) found in complexes 1, 3, 4, and 5 may be regarded as spectroscopic references of [Fe]
hydrogenases in the various enzymatic states.
The five-coordinate, sixteen-electron manganese(I) complex of some biological relevance, [Mn(CO)3(S-C6H4-NH)]-, stabilized by S,N π-donation of the bidentate [S-C6H4-NH]2-, was prepared by employing the dichalcogen synthetic technology.
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