Crystal structure of nitrido[5,10,15,20-tetrakis(4-methylphenyl)porphyrinato]manganese(V)

In the title compound the Mn Nnitride distance is 1.516 (4) Å. The Mn atom is displaced from the plane defined by the four equatorial nitrogen atoms toward the nitride ligand by 0.3162 (6) Å.

The title compound, [Mn(C 48 H 36 N 4 )(N)], is a manganese(V) complex with the transition metal in a square-pyramidal coordination geometry and a nitride as the axial ligand. The complex resides on a crystallographic inversion center and only one half of it is symmetry independent. The Mn V atom and the nitride N atom are equally disordered across the inversion center. The Mn N distance is 1.516 (4) Å . The Mn V atom is displaced from the plane defined by the four equatorial nitrogen atoms toward the nitride ligand by 0.3162 (6) Å .

Chemical context
Tetrapyrrole ligands have been used as a supporting ligand to stabilize high-valent, manganese compounds with manganese in 5-coordination and nitride ligands with short Mn N bond lengths. These complexes are characterized by Mn N distances of approximately 1.5 Å and the central metal displaced from the plane of the four equatorial N atoms toward the nitride ligand by up to 0.55 Å . In the course of our studies of Mn complexes we prepared and isolated the title complex, 5,10,15,20-tetrakis-tetratolylporphyrinatonitridomanganese(V) (I), and conducted its structural characterization to investigate how its geometry compares to that of its congeners.

Structural commentary
In the crystal structure of the title complex (I) (Fig. 1), the central Mn V atom possesses a square-pyramidal geometry. The equatorial plane is formed by the four nitrogen atoms of the porphyrin whereas the apical position is occupied by the nitride ligand. The complex resides on a crystallographic inversion center and only one half of it is symmetry independent. The Mn1 atom and nitride ligand atom N1 are equally disordered over two positions. This crystallographic behavior (disorder about an inversion center) was also observed in the case of (II). Whereas both complexes exhibit inversion symmetry, the Mn-N distances in them are not equal pairwise (as one would expect based on the fact that only one half of the complex is unique) because the Mn V atom is displaced from the equatorial plane not perpendicularly to it but at a small angle. Thus, the Mn-N distances in (I) range from 1.958 (2) to 2.070 (2) Å and between 1.983 (2) and 2.060 (2) Å in (II). The selected geometrical parameters for (I)-(VI) are presented in Table 1. A somewhat counterintuitive trend correlates the average Mn-N(eq) distance and the displacement of the Mn from the equatorial plane: the shorter the Mn-N(eq) distance, the larger the displacement. The correlation between the Mn-N(eq) distances and Mn N distance is not consistent, but in general the shorter the Mn-N(eq) distances, the longer the Mn N bond length, as might be expected. We have also conducted a CSD search for Mn V complexes with manganese in six-coordination and with a nitride ligand and found seven relevant compounds, but none of them was a porphyrin or a porphyrin derivative. The intention was to determine whether the expected metal-ligand bond lengthening occurs as the metal coordination number increases. It was found that for the five-coordinate (I)-(VI) the average Mn N distance is 1.54 (5) Å , whereas for the seven six-coordinate complexes this distance is 1.527 (10) Å . A molecular drawing of (I) shown with displacement parameters at the 50% probability level. All H atoms and the disordered mates of atoms Mn1 and N1 are omitted. [Symmetry operator (1): Àx + 1, Ày + 1, Àz.]

Figure 2
A packing diagram of (I) shown along the [001] direction. All H atoms are omitted.
Thus, the difference in the nature of the ligands (porphyrin vs tetra-azacyclo-tetradecane) accounts for the prediction 'reversal'.

Supramolecular features
Whereas there are possible weak non-classical interactions such as C-HÁ Á Á and C-HÁ Á ÁN(nitride) ( Table 2), nostacking interactions are detected. The molecules pack forming porphyrin/tolyl layers along the [100] direction with a 14.2619 (10) Å separation between identical layers (Fig. 2). The dihedral angle between the adjacent porphyrin core planes within the same layer is 30.037 (4) .
where TTP is the dianion of meso-tetratolylporphyrin (2.08 g, 2.65 mmol) was dissolved in methanol and eluted down an alumina column with methanol. The methanol was removed and the product redissolved in 400 ml dichloromethane. This solution was treated with 12 ml of an ammonia solution made by diluting 2 ml of concentrated ammonia with 10 ml of water and allowed to stir for fifteen minutes. A 10% sodium hypochlorite solution (6 ml) was added and the reaction was stirred an additional 15 minutes, resulting in a red solution. The solution was then washed with two 100 ml portions of water to remove the excess ammonia and hypochlorite and the sodium chloride formed during the reaction. The filtrate was placed on a neutral alumina column and the product was eluted with dichloromethane. Unreacted manganese(III) porphyrin can be recovered by eluting with methanol. The product was dried under reduced pressure. UV-vis ( max 535, 421 nm) are in excellent agreement with those obtained by Buchler et al. (1982)

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. All hydrogen atoms were included in the structure-factor calculation at idealized positions and were allowed to ride on the neighboring atoms with relative isotropic displacement coefficients.