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

Abstract

Treatment of an aryl-sec-alkyl unsymmetrical thiourea (Tu) with Cu(II)X(2) (X = I, Br) transform the thiourea (Tu) into a thioamidoguanidino (Tag) moiety with concomitant reduction of Cu(II) to Cu(I), which forms a [Cu(2)(I)(μ(2)-X)(2)Tag(2)] (X = I (for A) and X = Br (for B)) complex. Meanwhile, the treatment of same unsymmetrical thiourea (Tu) with Cu(I)X (X = Br) forms a stable cluster with a [Cu(I)(3)(μ(2)-S)(4)Tu(4)X(3)] core (C). Single crystal X-ray diffraction revealed that compounds A and B exhibit 1D chain with a Cu(2)(μ(2)-X)(2) core, whereas compound C is a Cu(I)(3)S(4)Br(3) 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 Cu(2)I(2) core is perfectly rhomboidal where the iodine atoms are trans oriented. However in compound B, the Cu(2)Br(2) 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 Cu(I)(3)S(4)Br(3) cluster in compound C contains one tri- and two tetra-coordinated Cu(I) centers. The Cu(I) cluster in C contains a Cu(2)(μ(2)-S)(2) rhomboidal plane exhibiting a chair and a boat form containing the Cu(I)(3)S(3) unit. In compounds A and B, the two Cu(I) centers are μ(2)-X bridged and have a μ(1)-S linkage, whereas in compound C the linkages are opposite having four μ(2)-S bridges and three μ(1)-Br linkages.