- A rare μ-hydroxo-bridged species. Synthesis, structure, and properties of μ-hydroxo(tetraphenylporphyrinatomanganese(III))(phthalocyaninato-(azido) chromium(III)), [(TPP)Mn-O(H)-CrPc(N3)]
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A novel ditetrapyrrolic, heteroleptic, and heterometallic (Mn-Cr) μ-hydroxo-bridged complex has been prepared, and its structural and general properties have been studied. The species μ-hydroxo(tetraphenylporphyrin- atomanganese(III))(phthalocyaninato(azido)chromium(III)), [(TPP)Mn-O(H)- CrPc(N3)], isolated as a chloronaphthalene (CINP) solvate, has been structurally characterized by single-crystal X-ray work. The two (TPP)Mn and CrPc(N3) fragments are held together by the bridging μ-hydroxo ion with long Mn-O [1.993(5) A] and Cr-O [1.976(5) A] bond distances and a Mn-O(H)-Cr angle of 163.7(3)°. The five-coordinate Mn center in the (TPP)Mn fragment is displaced from the TPP rigorously planar central N 4 core by 0.128 A, and the environment is typical of a Mn III high-spin site. The six-coordinate CrIII in the CrPc(N3) moiety lies practically in the plane of the phthalocyanine macrocycle (displacement toward the azido group: 0.054 A). The average Mn-Npyr and Cr-Npyr bond distances are 2.011(6) and 1.982(6) A, respectively, and the Mn-Cr bond distance is 3.929(2) A. The porphyrin and phthalocyanine rings are in an almost eclipsed position [5.16(2)°], and the mean planes of the two macrocycles form a dihedral angle of 5.79(4)°. Crystal data for [(TPP)Mn-O(H)-CrPc(N3)] ·2CINP, C76H45CrMnN15O·2C 10H7Cl: a = 16.645(3) A, b = 17.692(4) A, c = 25.828(5) A, α = 90°, β= 98.79(3)°, γ= 90°, space group P21/c (No. 14), V = 7517(3) A3, Z= 4, R1 = 0.086, and wR2 = 0.267. IR-and UV-vis-near-IR spectral and room temperature magnetic susceptibility data of the [Mn-Cr] species are also presented.
- Donzello, Maria Pia,Bartolino, Laura,Ercolani, Claudio,Rizzoli, Corrado
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p. 6988 - 6995
(2008/10/09)
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- Metal Complexes with Tetrapyrrole Ligands XXXIII. Preparation of Azidochromium(III)-, Azidomanganese(III)-, and Azidoiron(III) Porphyrins and their Photolysis to Terminal or Bridged Nitridometal Porphyrins
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Azidometal(III) porphyrins, e.g.M(TTP)N3 1 Aa - 1 Ca (M = Cr, Mn, Fe), are transformed into nitrido complexes on irradiation with ultraviolet light.Thus, Cr(III) or Mn(III) complexes, e.g.Cr(TTP)N3 or Mn(TTP)N3, yield Cr(V) and Mn(V) complexes with terminal nitride ligands, e.g.Cr(TTP)N (1 Ab) or Mn(TTP)N (1 Bb) with concomitant liberation of 1 mol of N2.However, the Fe(III) complex Fe(TTP)N3 produces the mixed-valence μ-nitrido-bis complex, 2N (1 Cg) and about 1.2 mol of N2 per mol of Fe.The azidometal(III) porphyrins are prepared from the corresponding hydroxo- or μ-oxo-metal(III) porphyrins and hydrazoic acid in benzene. - Key words: Chromium Porphyrins; Manganese Porphyrins; Nitridometal Complexes; Photolysis of Azido Complexes
- Buchler, Johann Walter,Dreher, Christine
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p. 222 - 230
(2007/10/02)
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- Study of (Tetraphenylporphinato)manganese(III)-Catalyzed Epoxidation and Demethylation Using p-Cyano-N,N-dimethylaniline N-Oxide as Oxygen Donor in a Homogeneous System. Kinetics, Radiochemical Ligation Studies, and Reaction Mechanism for a Model of Cytochrome P-450
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Oxygen transfer from p-cyanodimethylaniline (p-CNDMANO) to cyclohexene as well as "intramolecular" oxygen transfer accompained by demethylation to yield p-cyanomonomethylaniline (p-CNMMA) are strongly catalyzed by ligated (tetraphenylporphinato)MnIII (i.e., XMnIIITPP).These reactions have been studied in dry, oxygen-free benzonitrile.Radiochemical studies show that H2O (or TOH) is not bound to XMnIIITPP in aprotic solvents so that the MnIII moiety is pentacoordinate.Oxygen transfer occurs through the reversible formation of the hexacoordinated species p-CNDMANO*MnIII(X)TPP.This species decomposes to p-cyanodimethylaniline (p-CNDMA) + O=MnV(X)TPP.Reactions of cyclohexene with O=MnV(X)TPP yields cyclohexene epoxide and XMnIIITPP whereas p-CNMMA is formed directly from the p-CNDMANO*MnIII(X)TPP complex.The rates of product formation are shown to be dependent upon the nature of the ligand (X- = F-, Cl-, Br-, I-, OCN-).In the absence of the axial ligand X-, the rates of reaction are extremely slow.Thus, the MnIII C2-cap-porphyrin (XMnIIICAPTPP), which can only form an O=MnV porphyrin species wherein the Mn moiety is not complexed to X- as a sixth ligand, shows almost no tendency to act as a catalyst for oxygen transfer.The necessary presence of the axial ligand X- and the dependence of rate upon X- requires the structure of the oxygen transfer species to be quivalent to O=MnV(X)TPP.A kinetic analysis is presented (Scheme III) which has allowed the determination of the influence of the ligands X- upon the various rate constants (Table IV) involved in the overall oxidations.By employing p-CNDMANO as oxygen donor, multiple catalytic turnovers without loss of porphyrin have been realized.
- Powell, Michael F.,Pai, Emil F.,Bruice, Thomas C.
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p. 3277 - 3285
(2007/10/02)
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- 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
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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.
- Camenzind, Mark J.,Hollander, Frederick J.,Hill, Craig L.
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p. 3776 - 3784
(2008/10/08)
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