Sporadic binding of perchlorate and dicyanamide ions in trinuclear CuII2NiII complexes with a reduced di-Schiff base ligand: Synthesis, structures and spectral properties

Unusual site selection of perchlorate and dicyanamide anions have been found in two new trinuclear CuII2NiII complexes with a reduced salen type Schiff base ligand. [Display omitted] •Cu(II)-Ni(II) heterometallic complexes based on “Cu(II)-metalloligand”.•“Metalloligand” was derived from a reduced Schiff base ligand.•Rare site selection of perchlorate and dicyanamide ions to the terminal Cu(II) centers.•Linear trinuclear complexes having center of inversion at the central Ni(II). Two new unusual trinuclear linear heterometallic complexes, [(CuLR)2Ni(ClO4)2{CO(CH3)2}2]·0.17H2O (1) and [(CuLR)2Ni(N3C2)2(0.5CH3OH)2] (2) have been synthesized by using [CuLR] as a “metalloligand” (where H2LR=N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine) in presence of anions perchlorate and dicyanamide, respectively. Both the complexes have been diagnosed by elemental analysis, spectroscopic investigations, and single crystal XRD study. In these complexes, the terminal “ligand complex” [CuLR] coordinates to the central nickel atom via double phenoxido oxygen atoms bridge, resulted in a linear trinuclear structures. In both structures, the anions (perchlorate for 1 and dicyanamide for 2) coordinate to the terminal Cu(II) centers of the trinuclear unit (Cu(II)-Ni(II)-Cu(II)) to complete the distorted octahedral geometry around Cu(II); whereas the central Ni(II) metal ion remains in square planar geometry. The binding of perchlorate or dicyanamide to the terminal Cu(II) instead of central Ni(II) ion is rather unusual compared to the complexes of analogous unreduced species.