Authors:B. Csákvári, É. Csákvári, P. Gömöry, and A. Vértes
The donor strength of oxygen atoms in the Si−O−C and Si−O−Si groups has been studied by Mössbauer spectroscopy, using SnI4 as acceptor. At 80 K trimethylalkoxysilanes and the disiloxanes studied show characteristic isomer shifts on the basis of
which the existence of pentacovalent SnI4·D and hexacovalent SnI4·D2 may be assumed. The changes in isomer shift due to the first and second oxygen atoms are −0.60 and −0.55 mm/sec, respectively.
The coordination number is determined by the steric requirements of the donor relative to the coordination sphere of the acceptor,
provided that the donor strength is sufficiently high. No donor-acceptor interactions have been observed with compounds of
the-(OSiR2)-O-type. In the case of hexamethyldisiloxane, iodine is displaced from the coordination sphere. No quadrupole splitting has
been observed in any of the cases studied. Thus the ratio of point charges assignable to the iodine and the donor oxygen atom
is 6:1 for the trigonal bipyramidal arrangement; for a tetragonal pyramidal structure the angle between the xy plane and the
Sn−I bond is ∼35°.
Authors:Cs. Várhelyi Jr., G. Pokol, Á. Gömöry, A. Gănescu, P. Sohár, G. Liptay, and Cs. Várhelyi
chelates of the type [Ni(II)(Diox.H)2], ((Diox.H)2:
various α-dioximes) have been studied by means of FTIR, NMR, MS data
and various thermoanalytical methods (TG, DTA, DTG, DSC). In some cases kinetic
parameters of the thermal decomposition of the complexes were also calculated
using Zsak’s ‘nomogram method’. The mechanism of
the decomposition processes was characterised on the basis of mass spectra.