A solution and solid state study of niobium complexes University of ...

Chapter 4
Figure 4.9: A view of the planes constructed through the coordinated acetylacetonate
ligands.
Planes constructed through the four-coordinated acac ligands form a square that
encloses the niobium “cage”. Due to symmetry, the opposing planes are parallel to
each other, forming a perfect parallelogram as displayed in Figure 4.9.
The bite angles of the acac ligands are very similar at 80.03 (10) ° for O2–Nb1–O3
and 79.04 (11) ° for O7–Nb2–O8. The Nb–O bond lengt hs differ from 2.197 (2) Å for
Nb1–O2 and 2.088 (2) Å for Nb1–O3, whereas that of Nb2–O7 and Nb2–O8 is 2.091
(3) Å and 2.201 (3) Å, respectively. This is a common phenomenon for acac type of
ligands 8 , where the metal-oxygen bond of the bidentate ligand differs significantly in
bond length. The rest of the Nb–O bond lengths range from 1.817 (2) Å to 2.201 (3)
Å (Table 4.5). All the trans O–Nb–O angels deviate from 180 ° by between 9 and
19 °. The trans O–Nb1–O angles range from 161.84 (10) to 171.85 (10) ° while the
trans O–Nb2–O angles range from 162.89 (11) to 169.62 (10) °. From this it can be
seen that the trans O–Nb2–O angle around Nb2 has a smaller range than the trans
O–Nb1–O angle around Nb1 (Table 4.6).
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