| Summary: | Bibliography: p. 130-136. === The crystal and molecular structures of phenyl,
2-mercaptopyrimidine mercury(II) and phenyl,mercaptobenzene mercury(II) have been determined by the
methods of X-ray crystallography. The interaction between mercury and sulphur is investigated. This
interaction is of interest both biochemically and toxicologically. More specifically, secondary Hg---S
interactions are found to mimic that observed in NMR exchange processes, where they undergo a transition
state as a four-membered bridging intermediate. Structural correlations between compounds containing at
least one mercury - sulphur covalent bond are examined. The coordination geometry about the mercury atom
is generally found to be distorted tetrahedra or octahedra, with a very strong tendency to retain the linear
character of the R - Hg - S angle. The electronegativity of sulphur is found to be the most influential parameter
in determining the coordination geonetry of the mercury atom. The transition from four- to six-coordinated
structures is examined but did not reveal unambiguously whether this occurs by an SN3 or
(SN2)2 disubstitution process. The four-membered bridging structure formed by secondary Hg---S
interactions is investigated to determine whether minimum energy pathways are evident. However,
there is no evidence for pathways representing exchange as observed in solution.
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