The structure of a triclinic crystalline form of l,2,3,4,5,6,7,8-octaethylporphinatonickel(II) has been determined from three-dimensional X-ray counter data. The crystals, grown from a pyridine-dioxane solution, have the space group PI with a unit cell of a = 9.924 (3) Á, b -10.564 (3) A, c = 7.617 (2) A, a = 97.66 (2)°, ß = 109.47 (3)°, and y = 92.35 (3)°w ith one molecule per unit cell. The observed and calculated densities are 1.31 (1) and 1.322 g/cm3, respectively. The structure was solved by Fourier methods and refined by least-squares techniques to a final conventional R factor of 0.045 (based on F) for the 2080 reflections having I > 3 . The metalloporphyrin is a centrosymmetric square-planar complex with Ni-N bond lengths of 1.957 (2) and 1.959 (2) Á. The macrocycle is effectively planar with an angle between the planes of adjacent pyrrole rings of 2.1°. There are marked differences between the structure in the triclinic crystalline form and in the tetragonal crystalline form of the same complex, particularly in the degree of nonplanarity of the porphinato core. Packing calculations seem to indicate the tetragonal modification is the lower energy form.Recently the structure determination of a tetragonal form of 1,2,3,4,5,6,7,8-octaethylporphinatonickel-(II) (NiOEP) has been published.1 There are two unusual features about this square-planar complex.The Ni-N distance is the shortest M-N bond yet reported for a metalloporphyrin, and the macrocycle is highly distorted, having in effect D2d symmetry. The angle between planes of adjacent pyrrole rings is 32.8°. Hoard2 has made extensive use of the data on this complex to examine the correlation between M-N distances and the geometry of the macrocycle in metalloporphyrins.The crystals of tetragonal NiOEP were grown from a mixture of benzene, nitromethane, and dichloromethane.More recently in an attempt to prepare a high spin Ni(II) complex, NiOEP was dissolved in a 1:1

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Supplementary Material Available: Listings of torsion angles in the coordinated P(/-Bu)3 ligand (Table V), typical values for the distances and angles in coordinated P(r-Bu)3 (Table VI), anisotropic temperature factors (Table VIII), interatomic distances and bond angles in the phosphine (Table IX), the average geometry of coordinated P(r-Bu)3 (Table X), and observed and calculated structure factors (Table XI) (27 pages). Ordering information is given on any current masthead page.

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