Two molecule-bridged bis(tetracyanoiron) complexes [(NC)(4)Fe(BL)Fe(CN)(4)](n)()(-), BL = 2,2'-bipyrimidine (bpym) and 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz), were studied by EPR, UV/vis/near-IR and IR spectroelectrochemistry (n = 2-5) in aprotic media. Following these results, the Fe(2)(2.5) formulation is the correct valence description for the metal centers in the bptz-bridged trianion (K(c) = 10(14.6) in CH(3)CN), whereas the localized Fe(III)/Fe(II) formulation is appropriate for the bpym-bridged system (K(c) = 10(5.4) in CH(3)CN and 10(6.4) in CH(2)Cl(2)). In contrast to common perception, the larger tetrazine-bridged system with the longer metal-metal distance exhibits much stronger metal-metal coupling than the bpym-bridged analogue, a consequence of the very low lying pi LUMO of tetrazines with high MO coefficients at the coordinating nitrogen centers.
TAS+ salts (TAS = (Me2N)3S) of the sulfur diimide anions Me3XNSN- (X = C (1a), Si (1b)) were prepared by Si-N bond cleavage from the corresponding sulfur diimides Me3XNSNSiMe3 and TAS-fluoride ((Me2N)3S+Me3SiF2-) and characterized by X-ray crystallography and multinuclear NMR spectroscopy. According to the experimentally determined bond lengths and theoretical calculations, the Me3XNSN- anions are best described as thiazylamides Me3X-N-S identical to N rather than sulfur diimides Me3X-N=S=N. In agreement with the calculated and experimentally determined structures of the isoelectronic thionylimides RNSO, 1a adopts the Z-configuration, which is electronically favored due to anomeric effects. The electronically disfavored E-configuration of 1b in the solid state can be explained by weak anion-cation interaction.
The synthesis of m-fluorosulfinylaniline together with a tentative assignment of the vibrational, NMR and mass spectra, are reported. Quantum chemical calculations predict two stable conformers, with very similar energies, both of which possess in the liquid phase syn structure of the -N=S=O moiety (syn of the S=O double bond relative to the C-N single bond). Both conformers belong to C S symmetry group and differ by relative orientation of the fluorine atom and the NSO group. However, the FT-IR, FT-Raman and NMR spectra do not allow a distinction between these two conformers. The experimentally observed spectral data (FT-IR, FT-Raman, 1 H and 13 C and GC-Mass Spectrometry) of the title compound are compared with the spectral data obtained by quantum chemical calculations and gauge including atomic orbital (GIAO) method (DFT/B3LYP approximation using 6-311+G(df), 6-311++G(df,pd) and cc-pVTZ basis sets). Moreover, Natural Bond Orbital (NBO) analysis is applied for studying the stability of the molecule upon charge delocalization in order to provide an explanation of its electronic properties.
The molecular structure and conformational properties of ((trifluoroacetyl)imido)(trifluoromethyl)sulfur fluoride,
CF3C(O)NS(F)CF3, were determined by gas electron diffraction (GED) and vibrational spectroscopy
(IR (gas) and Raman (liquid)). Furthermore, quantum chemical calculations (HF, MP2, and B3LYP with
6-31G* basis sets) were performed. The vibrational spectra were assigned by comparison with related molecules
and calculated (HF and B3LYP) frequencies and intensities. According to the GED analysis the main conformer
(90(6)%) possesses an anti−syn structure with anti orientation of the N−C bond relative to the F−S−CF3
bisector and syn orientation of the CO bond relative to the NS bond. The second conformer (10(6)%)
possesses a syn−syn structure. The experimental Gibbs free energy difference (ΔG° = 1.3(4) kcal/mol) is
reproduced correctly by the two quantum chemical methods (1.35 kcal/mol from MP2 and 1.04 kcal/mol
from B3LYP). The conformational properties of this compound are in contrast to those of imidosulfurous
difluorides, RNSF2, and dichlorides, RNSCl2, for which only syn structures around the NS double bond
were observed.
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