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.