Pyrolytic reactions of azidochromium(III) porphyrins and azidoiron(III) porphyrins in the solid state
摘要:
Azidochromium(III) tetraphenylporphyrin. Cr(III)(tpp)N3 (tpp = 5,10,15,20-tetraphenylporphyrinato), and azidoiron(III) tetraphenylporphyrin, Fe(III)(tpp)N3, in the solid state, were pyrolysed under 10(-5) -10(-6) torr at around 250-degrees-C, liberating nitrogen gas to afford Cr(II)(tpp) and Fe(II)(tpp) as final products, respectively. Cr(v)(tpp)N formed in the process of the Cr(III)(tpp)N3 pyrolysis is reduced to Cr(II)(tpp), although pure Cr(v)(tpp)N prepared independently is not pyrolysed under the same conditions. In the presence of dioxygen in the toluene solutions of these pyrolysed products, Cr(IV)(tpp)O or [Fe(tpp)]2O is formed. The mechanisms of these reactions in the solid state are discussed in comparison with those in solution.
Azidomanganese(III) meso-tetraphenylporphyrin, MnIII (tpp)N3, in the solid state was pyrolyzed around 236 °C to yield nitridomanganese (V) meso-tetraphenylporphyrin, MnV (tpp)N.
Detailed analyses for vibrational and dynamical magnetism of chromium nitride (CrN2−)-porphyrinato complex revealed that g-value anisotropy accelerates magnetic relaxations greater than the internal magnetic field from nuclear spin does.
Stereoelectronic Aspects of Inter-Metal Nitrogen Atom Transfer Reactions between Nitridomanganese(V) and Chromium(III) Porphyrins
作者:Lawrence A. Bottomley、Frank L. Neely
DOI:10.1021/ic960919c
日期:1997.11.1
Reactions of nitridomanganese(V) porphyrins with chromium(III) porphyrins resulted in the irreversible formation of nitridochromium(V) porphyrins and manganese(III) porphyrins. The progress of these reactions has been followed spectrophotometrically, electrochemically, and spectroscopically by EPR. Kinetic analysis of the spectrophotometric data obtained during these reactions for a variety of substituted porphyrins showed the reactions to be first order in each of the reactants. Rate constants were dependent upon the electronic and steric effects of the porphyrin substituent, upon the identity of the anion bound to the chromium(III) reactant, and upon the solvent dielectric constant. We propose that the mechanism of these nitrogen atom transfer reactions involves the nucleophilic attack of the nitridomanganese porphyrin donor on the cationic chromium(III) porphyrin acceptor facilitating a net, two-electron redox process mediated by a heterobimetallic mu-nitrido intermediate. This report represents the first systematic study of the stereoelectronic effects involved in the complete, inter-metal nitrogen atom transfer between two metalloporphyrins.