80584-26-5Relevant academic research and scientific papers
Synthesis, characterization, and reactivity of novel organochromium(III) porphyrin complexes
Toscano, Paul J.,Brand, Holger,DiMauro, Peter T.
, p. 30 - 35 (1993)
The preparations of the organometallic porphyrin complexes (TTP)CrR (TTP is the dianion of meso-tetra-p-tolylporphyrin; R is C6H5, C6H4tBu-p, or CH2SiMe3) are described. The new
Oxygen atom transfer reactions of chromium porphyrins: An electronic rationale for Oxo transfer versus μ-Oxo product formation
Woo, L. Keith,Goll, James G.,Benreau, Lisa M.,Weaving, Rob
, p. 7411 - 7415 (2007/10/02)
Treatment of (meso-tetra-p-tolylporphyrinato)chromium(IV) oxide, (TTP)Cr=O, with (octaethylporphyrinato)- chromium(III) chloride, (OEP)Cr-Cl, in benzene results in the reversible exchange of axial ligands to form (TTP)Cr-Cl and (OEP)Cr=O. The net result is a formal one-electron redox process. This occurs with a second-order rate constant of 0.14 ± 0.01 M-1 s-1 to form an equilibrium mixture with K = 2.7 ± 0.1 at 30°C (ΔH? = 15.4 ± 0.7 kcal/mol, ΔS? = -12 ± 2 cal/(mol·K), ΔH° = -2.0 ± 0.4 kcal/mol, and ΔS° = -4.6 ± 1.2 cal/(mol·K)). Use of pivalate in place of chloride on the Cr(III) complex causes no significant change in the rate of this one-electron redox process. The sterically protected Baldwin's C2-capped (porphyrinato)chromium(III) complex, (CAP)Cr-Cl, also undergoes oxygen atom transfer with (OEP)Cr=O at a similar rate. In addition, excess chloride inhibits the rate of oxygen transfer with chlorochromium(III) complexes. These results support an inner-sphere mechanism involving a μ-oxo intermediate which is formed after an initial ligand (chloride or pivalate) dissociation from the chromium(UI) reductant.
Metal complexes with tetrapyrrole ligands. 29. Synthesis and electron spin resonance spectra and electron nuclear double resonance investigations of nitridochromium(V) porphyrins
Buchler, Johann W.,Dreher, Christine,Lay, Kiong-Lam,Raap, Adriaan,Gersonde, Klaus
, p. 879 - 884 (2008/10/08)
Mononuclear pentacoordinated nitridochromium(V) porphyrins, nitrido(tetra-p-tolylporphinato)chromium(V), CrN(TTP), and nitrido(octaethylporphinato)chromium(V), CrN(OEP), are prepared by hypochlorite oxidation of the corresponding chromium(III) porphyrins, CrOH(TTP)-2H2O and CrOH(OEP)·1/2H2O, in the presence of ammonia. These remarkably stable species are identified by UV/vis, IR, and mass spectra. An investigation of these paramagnetic compounds by ESR and ENDOR spectroscopy has furnished evidence for the CrV(d1/dxy) state of the central metal and the coordination of a single axial nitrogen. The X- and Q-band ESR as well as the 14N ENDOR spectra are identical for both CrN(TTP) and CrN(OEP): At room temperature we find an isotropic signal at g0 = 1.9825 and an isotropic 53Cr hyperfine splitting a0(53Cr) = 2.83 mT. A superhyperfine splitting a(14N) = 0.27 mT due to five apparently equivalent 14N nuclei is observed. At 77 K an anisotropic ESR signal with g⊥ = 1.9945 and g∥ = 1.9583 and anisotropic hyperfine values of a⊥(53Cr) = 2.24 mT and a∥(53Cr) = 4.01 mT have been determined. 14N ENDOR spectra measured at 3.6 K serve to discern the axial and equatorial superhyperfine splitting constants: For Npyrrole, a⊥1 = 0.36, a⊥2 = 0.14, and a∥ = 0.31 mT, and for Naxial, a⊥1 = 0.37, a⊥2 = 0.34, and a∥ = 0.13 mT. The ESR and ENDOR parameters are characteristic for a d1 system with strong spin localization in the dxy orbital and nearly no spin localization in dz2, which may be the reason for the high stability of these complexes.
