Theodore F. Schaaf

Metal-silicon bonded compounds XVII. A 199Hg Ft NMR study of some silylmercury derivatives and selected organomercury compounds☆

Abstract The 199Hg NMR spectra were determined for a series of silylmercury derivatives of the form Hg(SiRR′R″)2 by Fourier transform techniques. A linear correlation between the chemical shift, δ(199Hg), and the sum of the orbital electronegativities on silicon is reported for symmetric species. The chemical shifts are also linearly dependent on the lowest energy UV absorption maximum for these derivatives. These observations are discussed in terms of the current theories dealing with chemical shifts of heavy nuclei. The 199Hg-29Si coupling constants have been tabulated with evindence presented indicating that these are dominated by the Fermi contact interaction. It has been found that these are dependent on the same energy terms as observed for the chemical shift. Limited studies are reported on solvent, concentration, and temperature dependence of the δ(199Hg) for these derivatives.

Metal-silicon bonded compounds : X. The molecular structures of 2,2,4,4,6,6,8,8-octamethyl-2,4,6,8-tetrasila-1,5-mercuracyclooctane and bis(triphenylsilyl) mercury

Abstract The crystal and molecular structure determinations of 2,2,4,4,6,6,8,8-octamethyl-2,4,6,8-tetrasila-1,5-mercuracyclooctane. Hg 2 Si 4 C 10 H 28 (I) and of bis-(triphenylsilyl)mercury, (Ph 3 Si) 2 Hg (II), are reported. The structures have been determined from single-crystal X-ray data collected by counter methods. Both molecules crystalize in the space group P 1 with one centrosymmetric molecule per unit cell. Each structure contains linear SiHgSi groups, with mercury-silicon distances of 2.490(4) A in I and 2.503(4) A II. In compound I the SiHgSi groups are linked by methylene bridges which form an eight member ring in the chair conformation. The cell dimensions for compound I are a 6.277(2), b 8.408(2), c 9.274(4) A, α 92.75(3), β 94.79(3) and γ 100.14(2)° with R 1 0.062 for 1809 observed reflections. The cell dimensions for compound II are a 9.999(4), b 11.727(8), c 7.654(5) A, α 99.87(5), β 115.35(4) and γ 98.41(4)°, with R 1 0.081 for 2394 observed reflections.

A PMR investigation of the self exchange of bis(trimethylsilyl)-, bis(trimethylgermyl)-, bis(trimethylstannyl)-, bis(methyldichlorosilyl)- and (trimethylsilyl)propynylmercury

PMR studies of the self-exchange of (Me3Si)2Hg and of (Me3Ge)2Hg have shown that these reactions proceed by a second order process with Arrhenius activation energies of 11.3±0.4 and 11.1±0.6 kcal/mole for the trimethylsilyl derivative in xylene and triethylamine respectively, and with 12.1±0.4 kcal/mole for the trimethyl-germyl derivative in toluene. Attempts to study the exchange of (Me3Si)2Hg in 4-methylpyridine and tributylphosphine were unsuccessful because of irreversible decomposition reactions. Quantitative results for the self-exchange of (Me3Sn)2Hg were unobtainable because of the rapid decomposition of this material above −20°, but the collapse of the 199Hg−1H satellites indicate that rapid exchange occurs. (MeCl2Si)2Hg was shown not to undergo rapid self-exchange although it does undergo exchange with (Me3Si)2Hg in less than 1 min. The rate of group exchange decreases in the order: The mixed compound Me3SiHg-CC-CH3 was shown to have rapid exchange of the propynyl group unlike bis(propynyl)mercury which does not undergo exchange readily.

Organosilylmercurials, a mass spectral study

Abstract The mass spectra of a number of organosilylmercurials and related compounds have been examined. Although the spectra are dominated by mercury free fragments, all compounds showed parent molecular ions and most showed other mercury containing fragments. Extrusion of mercury was found to be the most important fragmentation process and was supported by metastable peaks in several examples. Bis(triethylsilyl)mercury showed a metastable peak for the formation of Et 3 Si + from the parent molecular ion. This was the only other example of the fragmentation of a parent molecular ion supported by a metastable fragment. The effect of substitution of longer chain alkyl, alkene, phenyl, and chlorine groups on bis(trimethylsilyl)mercury are reported and discussed.

Metal—silicon bonded compounds: XIV. The electronic spectra of silicon—mercury derivatives

The ultraviolet and visible spectra of compounds of the general formula Hg(SiCl3-xRx)2 where R  Me, Ph are reported. In addition spectra have been obtained on the compounds Hg(GeMe3)2, Hg[Si(SiMe3)3]2 and the cyclic compound HgSi(Me2)CH2SiMe2HgSiMe2CH2SiMe2. In cyclohexane all compounds show three characteristic bands, two at ≈4 eV and on at ≈6 eV. Extended Huckel calculations have been used to obtain a qualitative energy level scheme and to make tentative assignments for the transitions. The 4 eV transitions have been assigned to transitions from the ground state, 1A1, to be 1B1 and 1A2 states respectively and the 6 eV transition to a transition to an excited 1A1 state. The orbitals involved are principally centered on the mercury atom with their energies perturbated by the attached silicon moieties.