Extremely Bent Cyanide Coordination at a Preorganized Dinickel Site and Assembly of a Starlike Nonanuclear Complex from the Constrained Dinickel Building Blocks

Abstract

An extremely bent cyanide coordination at a dinickel scaffold is reported. Preorganization of two nickel ions is achieved by means of a compartmental dinucleating pyrazolate ligand L-, setting up a bimetallic coordination pocket with constrained metal−metal separation. The mixed-spin dinickel(II) complex LNi2(CN)(MeCN)2 (1) has been characterized by X-ray diffraction. The MeCN bound to the high-spin nickel(II) ion can be removed or replaced by other ligands, e.g., by the cyanide ligand of a tetracyanonickelate(II) moiety to give the starlike nonanuclear complex {[LNi2(CN)]4[Ni(CN)4]}(ClO4)6 (2) that contains four of the constrained pyrazolate-based dinickel(II) fragments grouped around a central tetracyanonickelate(II) unit, as revealed by X-ray crystallography. Spectral and electrochemical properties of 1 and 2 are reported, and the formation of reduced mixed-valent NiINiII species is investigated by IR and UV/vis spectroelectrochemistry.