Dissertation

|3.3 NN-NHC-Ligand bbip: Toward Second Generation Catalysts|
3.3.3 Structural Characterization of ip-Type Ligands
Slow recrystallization yielded suitable crystals for X-ray diffraction experiments of all prepared
organic compounds in this series of imidazophenanthroline derivatives (see figure 83). The
relevant distances and angles are gathered in table 12 on page 119.
Figure 83: Molecular structures of the prepared imidazophenanthroline derivatives: protonated ip
(left), bip (center) and bbip (right). Selected bond lengths and angles can be found in table 12.
The structural features observed for the organic compounds combine both, the general patterns of
phenanthrolines and those of the benzimidazole derivatives, respectively. Therefore, it is useful to
focus on the two coordination sites for the structural characterization of the new ip-type ligands
(the same numbering scheme was applied to all ip-type ligands in this thesis). With respect to the
phenanthroline coordination site, all ligands exhibit a number of typical similarities which can
be found in other phenanthroline derivatives as well (see chapter 3.1.1). As expected, the N,N’-
coordination environment with respect to the bond lengths and angles remains unaffected by the
changes at the imidazole part of the ligands.
Thus, the N1-C12 bond lengths and N2-C11 bond lengths are generally equidistant in this series
and vary only in the range between 1.352(2) Å and 1.367(9) Å. The C11-C12 distances vary
between 1.454(10) Å and 1.468(4) Å respectively without significant deviations. Furthermore,
minor variations in the C1-N1-C12 and the C10-N2-C11 bond angles between 117.2(2)° and
118.38(15)° were found in all ip derivatives. Between the N1-C12-C11 and the N2-C11-C12 bond
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