Optical spectra, electronic structure and aromaticity of benzannulated N-heterocyclic carbene and its analogues of the type CH(NR)E: (E = Si, Ge, Sn, Pb).

A series of benzannulated N-heterocyclic compounds containing divalent 14 group atoms, CH(NR)E, E = C, Si, Ge, Sn, Pb, have been studied by various experimental (vibrational and UV-vis spectroscopy) and theoretical (NICS, ISE, ACID) techniques. The methods used confirm 10 π-electron delocalization (aromaticity) in these heterocycles, however, the aromaticity sequences estimated by the criteria based on different physical properties do not coincide.

One-electron-mediated rearrangements of 2,3-disiladicarbene.

A disiladicarbene, (Cy-cAAC)2Si2 (2), was synthesized by reduction of Cy-cAAC:SiCl4 adduct with KC8. The dark-colored compound 2 is stable at room temperature for a year under an inert atmosphere. Moreover, it is stable up to 190 °C and also can be characterized by electron ionization mass spectrometry.

A new stable monomeric lead(ii) dithiolate Pb(SCH(2)CH(2)NMe(2))(2): an interplay between a dynamic "flip-flop" process in solution and conformational isomerism in the solid-state.

The structure and dynamic behaviour of monomeric lead(ii) dithiolate Pb(SCH(2)CH(2)NMe(2))(2) are studied by multi-nuclear NMR, IR and Raman spectroscopy in solution, as well as variable-temperature Raman spectroscopy and X-ray diffraction analysis in the solid-state, revealing an unusual dynamic "flip-flop" process in solution and reversible conformational isomerism of the chelated five-membered rings in the solid-state.

Two modifications formed by "sulflower" C16S8 molecules, their study by XRD and optical spectroscopy (Raman, IR, UV-Vis) methods.

Sublimation of sulflower, octathio[8]circulene C 16S 8 ( 1), on heating under high vacuum ( approximately 10 (-5) Torr) leads to successive formation of two modifications: a white film ( 1W) and a red polycrystalline solid ( 1R). When kept at room temperature for several weeks, 1W spontaneously turns pink, reflecting the monotropic phase transition 1W --> 1R. The accurate molecular and crystal structure of 1R has been studied using low-temperature (100 K) high-resolution single crystal X-ray analysis.

Can Sn(OCH2CH2NMe2)2 behave as a stannylene? Equatorial-axial isomerism in the tin(II)-iron(0) complex (Me2NCH2CH2O)2Sn-Fe(CO)4.

Equatorial-axial isomerism of the tin(II)-iron(0) complex (Me2NCH2CH2O)2Sn-Fe(CO)4 (), which indicates that the free Sn(OCH2CH2NMe2)2 () ligand can behave as a stannylene, has been revealed and studied by NMR and IR spectroscopy in solution as well as by Raman spectroscopy and X-ray diffraction analysis in the solid-state.

The Raman spectrum and aromatic stabilization in a cyclic germylene.

For the stable germylene, N,N'-di-tert-butyl-1,3-diaza-2-germacyclopent-4-en-2-ylidene, 2, the Raman line for the cyclic C=C stretching mode is strongly enhanced and shifted to longer wavelength, compared with that in reference compounds. The enhancement and frequency shift are even greater than those found for the corresponding stable silylene 1. These results, along with NMR evidence and theoretical calculations, suggest that the aromatic electron delocalization is even greater in the germylene than that in the silylene.

Probing the structure of the silylene complex (Cy3P)2Pt=SiMes2.; UV-Vis and pre-resonance Raman investigations.

The UV-Vis, pre-resonance Raman and IR spectra of the complex (Cy3P)2Pt=SiMes2 (1) were obtained as well as Raman spectra of some model compounds. The experimental data and the results of normal coordinate calculations show that the stretching vibration of the Si?Pt bond in 1 is not localized, the nuSi=Pt internal coordinate makes significant contribution to two normal modes with frequencies at 465 and 612cm-1, whose Raman intensity is enhanced by pre-resonance.

Synthesis and properties of stereoregular cyclic polysilanols: cis-[PhSi(O)OH](4), cis-[PhSi(O)OH](6), and tris-cis-tris-trans-[PhSi(O)OH](12).

New stereoregular cyclic polysilanols of the general formula [PhSi(O)OH]n (n = 6 and 12) have been selectively obtained in high yields by the reaction of cagelike oligophenylmetallasiloxanes with dilute solutions of hydrochloric acid at low temperatures. An alternative method was used to prepare cis-[PhSi(O)OH](4) from sodium phenylsiloxanolate, cis-[(Na(+))(4)[PhSi(O)O(-)](4)].(1-butanol)(x).