The Cyanurate Ribbon in Structural Coordination Chemistry: An Aggregate Structure That Persists across Different Coordination Environments and Structural Types

A series of nine coordination compounds is described, in which a
common supramolecular structure, a
ribbon of cyanurates, persists across variations in the metal center,
coordination geometry, coordination environment,
and crystal type. The syntheses and solid-state structures, as
determined by single-crystal X-ray diffraction, are
described for six of the complexes,
trans-[Cu(cyan-κN)2(H2O)2]·2Na(cyan)·4H2O
(1),
trans-[Cu(cyan-κN)2(NH3)2]
(5),
trans-[Cu(cyan-κN)2(NH3)2]trans-[Cu(cyan-κO2)2(NH3)4]
(6),
trans-[Ni(cyan-κN)2(NH3)4]
(7), (OC-6-33)-[Ni(cyan-κN)2(NH3)2(H2O)2]
(8), and
[Cu(cyan-κN)(PPh3)2]·2CDCl3
(9). The results are discussed together with
the
previously reported structures of the other three complexes,
[M(cyan-κN)(H2O)5](cyan)·2H2O
(M = Mn (2), Co (3),
Ni (4)). In all cases, the ribbon of cyanurates is
propagated through a recognition interaction involving a pair
of
hydrogen bonds between adjacent cyanurates, with a topological pattern
of the type

(8).
In eight of the nine
cases, the ribbon is linear, but for compound 5, which is
the first product of the reaction from which compound
6
is derived, the ribbon is crenelled. An unsuccessful attempt to
synthesize a product without the cyanurate ribbon in
the solid state is described. The possibility that the cyanurate
ribbon represents a traditional self-assembly in some
of these systems but not in others is discussed. It is concluded
that the formation of the cyanurate ribbon is a
determinative factor in the solid-state structural coordination
chemistry of the cyanurates of metals of the first
transition
series.