Rhenium(I) Tricarbonyl Complexes of <i>meso</i>-Tetraaryl-21,23-diheteroporphyrins
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Abstract
The
dithia/diselena <i>meso</i>-tetraarylporphyrins have a lesser
tendency to form metal complexes because of the larger size of the
heteroatom(s), which shrinks the cavity size, and the heteroatoms
also have poor coordinating ability to bind metal ions. The first
example of a rhenium(I) tricarbonyl complex of 21,23-diselenaporphyrin
was synthesized by treating 5,10,15,20-tetra-<i>p</i>-tolyl-21,23-diselenaporphyrin
with Re(CO)<sub>5</sub>Cl in chlorobenzene at reflux temperature and
its structural properties were compared with our earlier reported
rhenium(I) complex of tetraaryl-21,23-dithiaporphyrin. The crystal
structures of rhenium(I) complexes of diheteroporphyrins revealed
that the Re<sup>I</sup> ion binds to both the Se/S atoms and one of
the N atoms of the porphyrin core along with three terminal carbonyl
groups in an octahedral fashion. The rhenium(I) complexes of 21,23-diheteroporphyrins
are stabilized by a large counterion, the trichloro-bridged dirhenium(I)
ion. We also present a detailed account of the spectral and redox
properties of rhenium(I) tricarbonyl complexes of 21,23-diheteroporphyrins
