The Structure of Bis (t-butyl isocyanide) (tetracyanoethylene) nickel (0), Ni((CN)2C=C(CN)2)((CH3)3C—N≡C)

The structure of bis(t-butyl isocyanide)(tetracyanoethylene)nickel(0), Ni((CN)2C=C(CN)2)((CH3)3C—N≡C)2, has been determined at room temperature from three-dimensional X-ray data collected by counter methods. The structure has been refined by least-squares techniques to a final R factor on F of 3.6%, based on 1725 observations above background. The material crystallizes in space group C2h5-P21/c of the monoclinic system, with four molecules in a cell of dimensions a = 10.409 (8), b = 10.159 (8), c = 19.342 (14) Å, β = 112.33 (3)°. The observed and calculated densities are 1.24 (1) and 1.239 g/cm3, respectively. If one counts the tetracyanoethylene as a single ligand, the coordination about the Ni atom is approximately trigonal. The t-butyl isocyanide ligands have their expected geometry, and the average Ni–C distance is 1.866 (5) Å. The central two atoms of the tetracyanoethylene ligand are equidistant from the metal, with an average Ni–C bond length of 1.954 (4) Å. The C(CN)2 portions of the ligand remain planar, and the angle between the central C–C bond and the normals to the planes formed by these portions is 61.6 (5)°. The central C–C bond is 1.476 (5) Å, 0.137 (9) longer than that of 1.339 (8) Å in tetracyanoethylene, and concomitant with this lengthening the tetracyanoethylene ligand is nonplanar with the C(CN)2 groups bent away from the Ni atom. A simple correlation has been found between this bending angle and the increase of the central bond over the value in the free ligand. The central C–C vector is not coplanar with the plane formed by the Ni and the two bonding C atoms of the t-butyl isocyanide groups, but rather makes an angle of 82.2 (2)° with the normal to this plane. Alternatively, the angle between the normal to this plane and the normal to the plane formed by the Ni atom and the two central atoms of the tetracyanoethylene ligand is 23.9 (2)°. The Ni atom lies above and the four C atoms lie below the least-squares plane through these five atoms.