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

Coordination nickel-bridged fullerene polymer [{Ni­(Me3P)2}­(μ-η2,η2-C60)]∞ (1) has been obtained via reduction of a NiII(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 1. According to optical and electron paramagnetic resonance spectra, fullerenes are neutral in 1 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.