87337-88-0Relevant articles and documents
Synthesis, characterization, and ground electronic state of the unstable monomeric manganese(IV) porphyrin complexes diazido- and bis(isocyanato)(5,10,15,20-tetraphenylporphinato)manganese(IV). Crystal and molecular structure of the bis(isocyanato) complex
Camenzind, Mark J.,Hollander, Frederick J.,Hill, Craig L.
, p. 3776 - 3784 (2008/10/08)
The complexes diazido(5,10,15,20-tetraphenylporphinato)manganese(IV), MnIVTPP(N3)2 (1), and bis(isocyanato)(5,10,15,20-tetraphenylporhinato)manganese(IV), MnIVTPP(NCO)2 (2), have been synthesized by reacting MnIVTPP(OCH3)2 with either trimethylsilyl azide or isocyanic acid (HNCO) at ～-50°C. Both 1 and 2 are thermally unstable in solution at room temperature and decompose cleanly to MnIIITPP(X) (X = N3 or NCO). Variable-temperature magnetic susceptibility measurements, EPR spectroscopy, UV/visible spectroscopy, and infrared spectra of 1 and 2 are distinct from those exhibited by formally isoelectronic Mn(III) tetraphenylporphyrin π cation radical complexes. The properties of 1 and 2 are consistent with a high-spin d3 Mn(IV) ground electronic state. The infrared spectra of 1 and 2 show unusually low asymmetric stretching frequencies for the azide (ν = 1997 cm-1) and isocyanate (ν = 2127 cm-1) axial ligands. The complexes MnIVTPP(X)2 (X = OCH3, N3, NCO) show highly anisotropic EPR spectra at 12 K that are consistent with a d3 ion possessing a large zero-field splitting parameter, |D| > 0.6 cm-1. Crystals of MnIVTPP(NCO)2·0.5C6H5CH 3 were subjected to X-ray crystallographic analysis. The complex crystallized in space group C2/c, with cell dimensions a = 21.200 (2) A?, b = 17.582 (2) A?, c = 21.999 (3) A?, β = 108.81 (1)°, Vcalcd = 7762 (3) A?3, and Z = 8. The structure was refined by least-squares techniques to a final value of R = 0.0408 (Rw = 0.0512) based on 3027 observations. The coordination about the manganese atom is pseudooctahedral with the average Mn-Npyrrole distance of 1.970 A? and the average Mn-NNCO distance of 1.926 A?. Although the Mn-N4 unit is almost planar, the porphyrin core is distorted into a saddle shape by a large degree of quasi-S4 ruffling. The average displacement of the meso carbon atoms from the N4 plane is ±0.59 A?. The torsion angle of the two NCO ligands about the NNCO(A)-NNCO(B) vector is 81.5°. The orientation of the NCO ligands and the ruffling of the porphyrin core can be attributed to crystal-packing forces.
