Tricarbonyl[tris(1-methyl-1H-imidazol-2-yl-κN 3)methanol]manganese(I) trifluoromethanesulfonate

In the title compound, [Mn(C13H16N6O)(CO)3](CF3O3S), the MnI atom has a slightly distorted octahedral geometry. The three CO ligands have C—Mn—C angles in the range 89.44 (10)–92.31 (9)°, while the three N atoms of the tripodal ligand form significantly smaller N—Mn—N angles of 82.76 (2)–85.51 (6)°. The three N atoms of the tripodal ligand and the three carbonyl ligands coordinate facially. In the crystal, the trifluoromethanesulfonate counter anion is connected by a medium-strength O—H⋯O hydrogen bond to the hydroxyl group of the manganese complex.


Comment
The chemistry of manganese carbonyl complexes is of significant interest for at least two reasons. On the one hand there is a long standing interest in simple organometallic Mn(CO) 3 complexes, reflected by more than 2200 structures reported in the CCDC. On the other hand they are known to undergo a plethora of photochemical reactions, e.g. photochemical mediated cycloaddition reactions yielding complex organic ligand systems coordinated to a manganese center (e.g. Kreiter et al., 1994Kreiter et al., , 1995. Recently, manganese tricarbonyl complexes of tripodal N,N,N-ligands, like tris-(imidazolyl)carbinols (Breslow et al., 1983;Tang et al. 1978), have been shown to be photoinduced CO-releasing molecules (photoCORMs). The CO-release characteristics, e.g. the rate and half-life time for the release, are dependent on the ligands used to stabilize the Mn(CO) 3 core (Huber et al., 2012;Berends & Kurz, 2012;Brückmann et al., 2011;Kunz et al., 2009;Niesel et al., 2008). The manganese complex cation shows N,N,N-coordination in the solid state, which has also been observed for the corresponding rhenium(I) complex, in which the carbinol OH has been methylated (Herrick et al., 2008). The spectroscopic data in solution (IR and NMR, Huber et al., 2012) of the title compound are in accord with C 3v symmetry and therefore with the N,N,N-coordination found in the solid state. This indicates that coordination of the carbinol OH group is not favored, as found in other carbinol ligands (Stamatatos et al., 2009;Herrick et al., 2008).
The asymmetric unit of the title structure, consisting of a complex manganese cation and the trifluoromethanesulfonate counteranion, is shown in Fig. 1. The coordination polyhedron around the central manganese(I) atom is slightly distorted from octahedral symmetry. All Mn-N and Mn-C distances are in the expected range for a manganese(I) tricarbonyl complex. The three angles between the three CO ligands are near 90°, which is typical for the Mn(CO) 3 fragment (e.g. Kreiter et al., 1995). The three angles N-Mn-N are significantly smaller than 90° (82.76 (2)

Refinement
All H-atom positions were identified in difference Fourier maps. In the later stages of refinement the H atoms of the methyl groups and the H atoms of the rings of the tripodal ligand were refined using a riding model. The U iso values of the methyl H atoms were set to 1.5 times the equivalent isotropic displacement parameter of the C atom they are attached to.
The U iso values of the H atoms at the rings of the tripodal ligand were refined freely. The coordinates and the U iso value of the H atom of the carbinol function were refined freely.  The asymmetric unit of the title compound.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq