I. A. Garbuzova

VIBRATIONAL SPECTRA OF DISILENES. NORMAL COORDINATE ANALYSIS AND IDENTIFICATION OF THE V(SI=SI) STRETCHING VIBRATION

Abstract Experimental vibrational spectra are reported for three carbon-substituted disilenes along with data on normal coordinate analysis of several simplified disilene models. Calculations show that there is no normal mode in the disilene spectrum which is well-localized in the Si=Si bond. The Si=Si and Si-C stretching coordinates are heavily mixed. Their in-phase combination results in a normal mode with frequency in the region 450–550 cm −1 which manifests itself as a Raman line of variable intensity (the so-called v (Si=Si)). Their out-of-phase combination gives a mode in the region of about 700 cm −1 which shows itself as an intense Raman line (the so-called v S (Si-C)). Vibrations of an aromatic ring, if present in a disilene molecule, can also couple with the v (Si-Si). Particular eigenvector elements of the two modes in question and thus their potential energy distributions strongly depend on the structure and symmetry of a given disilene molecule. However, the contribution of the Si=Si stretching coordinate to the normal coordinate with frequency in the region 450–550cm −1 is always significant, justifying the designation of this mode as the v (Si=Si).

C-N migration of allyl- and propargyloxycarbonyl groups

Reactions of triisopropylphosphine with allyl-and propargyl-2-cyanoacrylates give corresponding 1,3-zwitterions. Under the action of phenyl-or 1-naphthylisocyanates the zwitterions exert C-N migration of allyl-or propargyloxycarbonyl groups affording carbamates. Atropisomerism at room temperature was established for the carbamate formed from 1-naphthylisocyanate.

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.

STRUCTURAL AND SPECTROSCOPIC STUDY OF CHELATE CARBONYL AND PHOSPHORYL ANTIMONY(V) COMPLEXES

Chelate complexes of antimony tetrachloride with dibenzoylmethane and (benzoylchloro-methyl)diphenylphosphine oxide were stndicd by X-ray diffraction, I R, and Raman spectroscopy. The antimony atom has a slightly distorted octahedral coordination in the complexes. The bond lengths in the chelate cycles are evidence for an appreciable electron delocalization in the O-C-C-C-0 and O-C-C-P-0 chains. Unlike the C3O2Sb chelate cycle, the chelate cycle with the phosphorus atom is nonplanar. The assignment of the stretching vibrations frequencies of the C-O, P-0, C-C, Sb-O, and Sb-CI bonds was presumably made on the basis of the IR and Raman spectral data.

Synthesis of yttrium, lanthanum, neodymium, praseodymium, and lutetium alkoxides and acetylacetonates

A convenient and practical method is proposed for the synthesis of lanthanide and yttrium alkoxides. The method involves dissolving the metals or their hydrides in a solution of dry HCl in the corresponding alcohol, with subsequent dehalogenation of the LnCl3 solution by an equivalent amount of alkali metal (Na, Li), The rareearth alkoxides are easily converted into acetylacetonates Ln(acac)3 by the action of acetylacetone.

Complexes of copper(I) halides with bis (trimethylsilyl) acetylene

Conclusions1.The authors have synthesized 1∶1 complexes of bis (trimethylsilyl) acetylene with copper(I) chloride and bromide, and investigated their vibrational spectra.2.Using x-ray diffraction analysis they have determined the dimer structure of the complex [(Me3SiC≡CSiMe3)·CuCl]2.

Vibrational Spectra and Rotational Isomerism of Polydialkoxyphosphazenes

FT-IR and Raman spectra of polydialkoxyphosphazenes (PDAP) — [P(OC m H2m + 1)2 = N] n — with m = 1–9 in the temperature interval from — 100 to + 100 °C were studied. It is shown that the temperature-dependent conformational changes occur in amorphous and mesomorphic phases due to internal rotation about P-O, C-O and C-C bonds in the side chains. The main chain does not change its form (presumably helix structure).

Normal coordinate analysis of disilenes and diphosphenes. The ν(SiSi) and ν(PP) stretching vibrations

Abstract Normal coordinate analysis (NCA) of some disilene and diphosphene molecules has been performed and compared with NCA of corresponding alkenes. For various models of disilenes containing the C 2 SiSiC 2 moiety, NCA shows that SiSi and SiC stretching coordinates are heavily mixed, their in-phase combination resulting in a normal mode in the region 450–550 cm −1 , while their out-of-phase combination is in the region 600–750 cm −1 . In contrast, the results of NCA for diphosphenes show that the vibration at ≈ 600 cm −1 is well localized, being predominantly νPP stretch (≈ 90% in PED).

Vibrational spectra and structure of caprolactamates of group II metals

Differences between the IR and Raman spectra of the dicaprolactamates of Mg, Ca, and Ba indicate differences in their structures. Barium dicaprolactamate has an ionic structure, while the dicaprolactamates of Mg and Ca are partially covalent and have one-dimensional chain structures with various types of NCO group (terminal, bridge). In solution the dicaprolactamates of Mg and Ca are associated on account of the formation of bridged NCO groups. It was shown that the vibration frequencies of the bridged NCO groups lie in the range 1580–1620 cm−1, and those of the terminal groups in the range 1550–1580 cm−1.

Vibrational spectra and the structures of alkali metal caprolactamates

Based on analysis of the IR and Raman spectra of Na and K caprolactamates it has been established that these exist not in two forms (lactamic and lactimic), as previously proposed, but rather in one form, intermediate in structure between these two forms, in which the negative charge is delocalized uniformly across the amide bond. It has also been shown that spectral bands at ∼1560 and ∼1400 cm−1 for these salts correspond to the antisymmetric and symmetric stretching vibrations of this bond.