Self-assembled Transition Metal Coordination Frameworks of ...

Chapter 3
3.3.3.1. Crystal structure of [Ni(HL’)]4(PF6)4- '/zCH3CH;OH- 2.8H;O (Ia)
The molecular structure of square grid complex (la) is given in Fig. 3.20 and
the coordination core about the Ni(II) centers with the atom numbering scheme is
given in Fig. 3.21. Selected bond lengths and bond angles are summarized in Table
3.7. The [Ni(HL')]44+ cation has four Ni(II) centers, organized by four
monodeprotonated ligands I-I2L', as a molecular square. Each metal center is
octahedrally coordinated by making use of atoms like one of the pyridyl nitrogen, it’s
nearby azomethine nitrogen and thiolate sulfur atoms of two perpendicular (HL')'
ligands. These two (HL')' ligands bind to Ni(II) in the mer configuration, with pairs of
sulfur atoms and pyridyl N atoms each bearing a cis relationship and the azomethine
N atoms keep a trans configuration, as found in related octahedral Ni(II)
thiocarbohydrazone [8,l6] and mononuclear thiosemicarbazone complexes [25,44].
As a result four fused five membered chelate rings share each metal center. The sulfur
atoms share a position of adjacent Ni(II) octahedra (Fig. 3.21) and thus connect the
centers to build a symmetrical molecular square (Fig. 3.22). The adjacent Ni---Ni
"distances are ~4.7 A {they vary from 4.679(2) A for Ni(l)---Ni(2) to 4.797(2) A for
Ni(2)---Ni(3)} and the angles subtended at the sulfur atoms Ni—S—Ni varies from
l65.30(l7)° for Ni(3)—S(4)—N(4) to 168.7l(17)° for Ni(l)—S(3)—Ni(4). The Ni---Ni
distances across the diagonals of the square are 6.749(2) A for Ni(l)--jNi(3) and
6.692(2) A for Ni(2)---Ni(4) and the Ni—Ni—Ni angles are ~90° {these vary from
88.73(4)° for Ni(2)—Ni(3)—Ni(4) to 90.82(4)° for Ni(l)—Ni(2)—Ni(3)}. The four Ni
atoms are in a plane with a maximum mean plane deviation of 0.0525(l7) A for Ni(l).
The sulfur atoms S(2) and S(4) are above and S(l) and S(3) are below this plane by
~0.2 A.
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