Investigation of phenyl derivatives of group IV elements using carbon-13 NMR spectroscopy

The tetraphenyl–metal, hexaphenyl–dimetal, and triphenylchloro–metal derivatives of the Group IV elements were examined using ¹³C NMR methods. Chemical shifts and metal–carbon coupling constants were obtained for all compounds studied.     

Furan derivatives of group IV elements (review)

Published data and the results of personal investigations on the methods of synthesis, chemical and physical properties, and biological activity of the furan derivatives of silicon, germanium, tin, lead, titanium, and zirconium are summarized.Latvian Institute of Organic Synthesis, Riga, Latvia, Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1587–1690, December, 1995 Original article submitted June 3, 1995.     

Hypercoordination in triphenyl oxinates of the group 14 elements

The triphenyl oxinates of the group 14 elements (M = Si, Ge, Sn, and Pb) contain the 8-hydroxyquinoline ligand (HOx), which can function in either a bidentate or monodentate fashion. The compounds Ph₃MO_x were prepared by reaction of the triphenylmetal chloride with HOx in the presence of an HCl scavenger triethylamine or, sodium acetate, and in the case of lead, with the sodium salt of 8-hydroxyquinoline. The interaction of the nitrogen with the central atom was studied through the use of the NMR chemical shifts of the central metal atom and the ¹⁵N atom of the ligand. The chemical shifts of the central metal provided evidence that the triphenylgermanium and silicon oxinates are uncoordinated while the triphenyltin and lead oxinates are five-coordinate. These conclusions are confirmed by molecular modeling, ¹⁵N chemical shifts and the metal-¹³C one bond coupling constants at the ipso carbon. The NMR data provides evidence that the strength of the interaction of the nitrogen with the metal increases from silicon and germanium to lead. Two peaks in the 5-coordinate region of the ²⁰⁷Pb NMR spectra can be rationalized with the postulate that strong interaction with lead produces two geometrical isomers. Two peaks were also present in the 5-coordinate region of the ¹¹⁹Sn NMR spectra at low temperatures indicating a rapid exchange between the two geometrical isomers at room temperature.     

Photoelectron spectroscopy of f-element organometallic compounds II. Tricyclopentadienyl derivatives of uranium(IV) and thorium(IV)

The photoelectron spectra of some cyclopentadienyI derivatives of uranium(IV) and thorium(IV), namely (C₅H₅)₃ ThCl, (C₅H₅)₃ UCl, (C₅ H₄ CH₃)₃ ThCl, (C₅ H₄ CH₃)₃ UCl, (C₅ H₄ CH₃)₃ UBr and (C₅ H₄ CH₃ )₃ UBH₄, are reported the metal 5f ionization has been detected in all the uranium derivative spectra and a simple molecular orbital scheme qualitatively accounts for the number and position of the observed low energy bands.     

Furan derivatives of group III elements

Methods for the synthesis of the furan derivatives of boron, aluminum, and thallium, the results from their physicochemical investigation, and their chemical transformations are summarized.Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 867–881, July, 1995. Original article submitted April 3, 1995.     

Nuclear magnetic resonance spectra of furan derivatives of IV B group elements (review)

Electronic and steric effects in furan derivatives were studied by the method of ¹H, ¹³C, ¹⁷O, and ²⁹Si NMR spectroscopy. The characteristic features of the influence of substituents on the screening and spin-spin interaction of ring nuclei in -substituted derivatives of furan in the presence of a second -substituent have been noted.Dedicated to Prof. A. R. Katritsky on his 65th birthday.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 879–890, July, 1993.     

Organometallic bis(p-hydroxyphenyl) derivatives of group IV elements and related compounds

Dimethyl- and diphenylbis(p-hydroxyphenyl) Group IV metal compounds have been synthesized. Scope and limitations of the following methods were investigated: (a) reaction of the halogen-metal exchange product of p-bromophenol and n-butyllithium with organometallic dihalides; (b) protection of the phenolic group with trimethyl or benzyl groups and subsequent hydrolysis or hydrogenolysis.     

Organometallic compounds having metal-metal bonds : XXV. Tetracarbonylnitrosyl-molybdenum and tungsten derivatives of the group IV elements

Tetraethylammonium salts of the anions [R₃M′M(CO)₅]^? react with NO⁺-PF₆^? to form the yellow to orange-red air stable products R₃M′M(CO)₄NO (M = Mo, R₃M′ = GePh₃, SnPh₃, SnMe₃, PbPh₃; M = W, R₃M′ = SiPh₃, SiPh₂Me, GePh₃, SnPh₃, SnMe₃, PbPh₃). Yields vary from 7 to 54% and M = Cr derivatives could not be obtained. Alternative synthetic procedures for the known complexes XW(CO)₄NO (X = Cl, Br, I) are described. IR spectroscopy established that the compounds exist as trans isomers in all cases. On the basis of carbonyl stretching force constants and NMR coupling constants, some qualitative comments are made on the bonding in the isoelectronic series [Me₃SnW(CO)₅]^?, Me₃SnW(CO)₄-NO, and Me₃SnRe(CO)₅.     

Photoelectron spectra of group V compounds. The elements: Sb4

The high-temperature He I photoelectron (PE) spectrum of gaseous Sb₄ is presented and assigned on the basis of the known PE ionisation energies of As₄ and P₄ and from SCC Xa eigenvalues and eigenvectors. Implications for the PE spectra of related antimony compounds are discussed.     

Photoelectron spectroscopy of phenyldihalophosphites

In order to explain the reactivity of aryldihalophosphites towards halophosphomum salts, photoelectron spectra of PhOPX₂ (X=F, Cl) were studied. Electron densities of boundary molecular orbitals (MO) for these compounds were calculated using the MNDO method and analyzed. Replacement of F by Cl was shown to substantially affect the orbital. When X= Cl, this MO embraces the whole of the OPX₂ moiety whereas for X=F it is localized on the P-O bond.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 323–324, February, 1993.     

Chromatography of organic derivatives of group IVB elements

Chromatographic aspects of the analysis of Group IV organometallic derivatives are reviewed. The emphasis is towards gas and liquid chromatography.     

A spectroscopic study of atomic interactions in aryl derivatives of group iv elements

Spectroscopic features (quantitative IR, Raman, and UV spectra) are discussed for group IV (M=C, Si, Ge, Sn) aryls, mainly R₃MC₆H₅ and R₃MCH₂C₆H₅, in order to distinguish features of the intramolecular interactions. Confirmation is obtained for the existing view on the electron-acceptor behavior of heteroatoms joined to aromatic rings. The effect is seen in the IR and UV spectra, which implies that the ground and excited states are perturbed. The effect of M on the ring is shown to be an over-all one; the positive (induction) component follows the electronegativity of M in a scale close to Gordy's, while the negative one increases somewhat from Si to Ge and Sn.The effects in M aryls are analogous to those in M alkenyls, in particular the - conjugation in a phenyl radical attached to Si, which is already known for M allyls.     

Photoelectron spectroscopy of chemisorbed atoms

We outline a theory of UV and higher-energy photoemission spectroscopy of chemisorbed atoms, that aims at the accurate calculation of inner electron binding energies and photoabsorption cross sections by including solid state and localized relativistic and correlation effects. It is based on an “atom on (in) solids” approach where one first extracts a surface potential and then uses it in a coupled Hartree–Fock theory to obtain self-consistently the shifts and splittings of atomic levels. A first application of this theoretical program has been carried out on Na on the Al(100) system, by calculating from first principles the binding energies of the Na 1s and 2s electrons. For a coverage of 1.23 × 10¹⁴ adatoms/cm² we find BE (1s) = 1075.2 eV and BE (2s) = 66.2 eV. Also, the Na 2p orbitals are found to split in the cylindrical symmetry by about 0.2 eV.     

Photoelectron spectroscopy of silver clusters

A comparison of x-ray photoemission from Ag clusters deposited on polygraphite and highly oriented pyrolitic graphite shows the influence of the support both on the valence band and on the core 3d level of the metal. Positive shifts have been obtained with respect to the bulk for the Fermi edge and the 3d peaks depending on the number of silver atoms deposited on the substrates. When the deposition is very small (cluster regime) the positive shifts of the binding energies are quite different for different substrates and cannot have a common origin. In contrast with recent work, we show that several effects contribute to these shifts: initial state effects like charge redistribution as well as final state effects like the hole-electron interaction.