Stable Cu(I) Complexes with Thioamidoguanidine Possessing Halide-Bridge Structure

Treatment of an aryl-sec-alkyl unsymmetrical
thiourea
(Tu) with CuIIX2 (X = I, Br) transform the thiourea
(Tu) into a thioamidoguanidino (Tag) moiety with concomitant reduction
of CuII to CuI, which forms a [Cu2I(μ2-X)2Tag2] (X
= I (for A) and X = Br (for B)) complex.
Meanwhile, the treatment of same unsymmetrical thiourea (Tu) with
CuIX (X = Br) forms a stable cluster with a [CuI3(μ2-S)4Tu4X3] core (C). Single crystal X-ray diffraction
revealed that compounds A and B exhibit
1D chain with a Cu2(μ2-X)2 core,
whereas compound C is a CuI3S4Br3 cluster. Compound A is centrosymmetric
due to the trans orientation of two Tag units whereas compound B is ascentric due to the cis orientation of two Tag units.
In compound A, the Cu2I2 core is
perfectly rhomboidal where the iodine atoms are trans oriented. However
in compound B, the Cu2Br2 core
is not perfectly rhomboidal (bowl shaped) and the bromine atoms are
cis oriented. It is interesting to note that although the Tag moiety
in compounds A and B contain two morpholine-O
atoms; only one of the morpholine-O atoms (O2) is involved in the
generation of three-dimensional network. The CuI3S4Br3 cluster in compound C contains
one tri- and two tetra-coordinated CuI centers. The CuI cluster in C contains a Cu2(μ2-S)2 rhomboidal plane exhibiting a chair and a
boat form containing the CuI3S3 unit.
In compounds A and B, the two CuI centers are μ2-X bridged and have a μ1-S linkage, whereas in compound C the linkages
are opposite having four μ2-S bridges and three μ1-Br linkages.