Linear Coordination Fullerene C₆₀ Polymer [{Ni(Me₃P)₂}(μ‑η²,η²‑C₆₀)]_∞ Bridged by Zerovalent Nickel Atoms

Abstract

Coordination nickel-bridged fullerene polymer [{Ni­(Me₃P)₂}­(μ-η²,η²-C₆₀)]_∞ (<b>1</b>) has been obtained via reduction of a Ni^II(Me₃P)₂Cl₂ and C₆₀ mixture. Each nickel atom is linked in the polymer with two fullerene units by η²-type Ni–C­(C₆₀) bonds of 2.087(8)–2.149(8) Å length. Nickel atoms are coordinated to the 6–6 bonds of C₆₀ as well as two trimethylphosphine ligands to form a four-coordinated environment around the metal centers. Fullerene cages approach very close to each other in the polymer with a 9.693(3) Å interfullerene center-to-center distance, and two short interfullerene C–C contacts of 2.923(7) Å length are formed. Polymer chains are densely packed in a crystal with interfullerene center-to-center distances between fullerenes from neighboring polymer chains of 9.933(3) Å and multiple interfullerene C···C contacts. As a result, three-dimensional dense fullerene packing is formed in <b>1</b>. According to optical and electron paramagnetic resonance spectra, fullerenes are neutral in <b>1</b> and nickel atoms have a zerovalent state with a diamagnetic d¹⁰ electron configuration. The density functional theory calculations prove the diamagnetic state of the polymer with a singlet–triplet gap wider than 1.37 eV