A cyanide-bridged 1-D helical chain involving both four- and six-coordinate nickel(II)

Abstract

A cyanide-bridged coordination polymer, {[Ni(tren)][Ni(CN)₄]} _n (tren = tris(2-aminoethyl)amine), has been synthesized by self-assembly of cis-[Ni(tren)]²⁺ and [Ni(CN)₄]²⁻ building blocks. In the molecular structure, the paramagnetic cis-[Ni(tren)]²⁺ cations are bridged by diamagnetic [Ni(CN)₄]²⁻ anions through two cis-cyanides to form a 1-D helical chain of {[Ni(tren)][Ni(CN)₄]} _n . The compound crystallizes with a centrosymmetrical space group, P2₁ /n, in which the helical chains are packed in alternating right- and left-handed chiralities with a helical pitch of 10.2566(3) Å (equal to the length of the b-axis), leading to the formation of a racemic compound. The crystal packing is stabilized by moderately strong hydrogen-bonding between primary amines of tren and nitrogens of terminal cyanide.

Keywords:

• Synthesis
• Crystal structure
• Cyano-bridged nickel(II) complex
• 1-D Helical chain
• Thermal study

Acknowledgments

The author thanks Prof. Pradyot Banerjee, Indian Association for the Cultivation of Science, Kolkata, for useful suggestions during the course of this work.