Thiocarbonyl S-sulfides have been considered thermodynamically less stable than the corresponding d i t h i i r a n e~. '~~] The driving force of the thermal isomerization of 2 to 9 is probably attributed to the rapid intramolecular ring closure, leading to thermodynamically far more stable 9, even when the equilibrium concentration of 8 is very low. Incidentally, no isomerization of 2 to the corresponding dithioester was detected. E.xperimenta1Procedure 2: A solution of 3 (681 mg. 2 mmol) in CH,CI, (500 mL). an aqueous solution (180 mL) of OXONE (18.4 g. 30 mmol) whose pH was adjusted to 5 --6 by adding 1 M KOH. and a catalytic amount of [MeN(C,H,,),]CI were stirred vigorously at 0 ' C for 6 d. During the reaction. 1 M KOH (2-3 mL) was added once or twice a day to maintain the pH of the aqueous layer between 5-6. The orange organic layer was separated. washed with cold water, dried over anhydrous MgSO,. and evaporated under reduced pressure at 0°C. The residue was dissolved in CH,CI, (2-3 mL) and the solution diluted with hexane. The resulting mixture was allowed to stand in a refrigerator and the first white crystalline crop, which consisted of by-products. was removed by filtration and the filtrate was cooled again in the refrigerator for 2 d. The orange crystals separated were collected by filtration and purified by mediumpressure liquid chromatography (silica gel, CH,CI,) to give 146 mg of 2. By-products of this oxidation consisted of the dithilrane oxide la, the sulfoxide 4, and the dicarbonyl compound 5, whose ylelds were not determined.

The methylation of a nickel(II) complex (CTPP)NiII of 2-aza-5,10,15,20-tetraphenyl-21-carbaporphyrin (CTPPH2) with the mild methylating agent methyl iodide yields novel stable organonickel(II) complexes:  diamagnetic (21-CH3TPP)NiII and two scarce paramagnetic species (2-NH-21-CH3CTPP)NiIIX and (2-NCH3-21-CH3CTPP)NiIIX (X = Cl, I). The demetalation procedure resulted in isolation of two 21-carbaporphyrin derivatives, methylated at the internal C(21) carbon atom, i.e., 2-aza-5,10,15,20-tetraphenyl-21-methyl-21-carbaporphyrin (21-CH3-CTPPH2) and 2-aza-2-methyl-5,10,15,20-tetraphenyl-21-methyl-21-carbaporphyrin (2-NCH3-21-CH3CTPPH). The methylation mechanism involves the oxidative addition of the methyl cation to the carbaporphyrin C(21) activated due to Ni−C coordination. These C-methylated macrocycles preserve their coordinating properties as the remetalation processes have been carried out. The reversible concerted addition of HX converts the diamagnetic (21-CH3TPP)NiII into the paramagnetic (2-NH-21-CH3CTPP)NiIIX. The axial coordination step is accompanied by a protonation of the peripheral nitrogen. The structures of (21-CH3CTPP)NIII (monoclinic, P21 /c; a = 15.055(3) Å, b = 15.795(3) Å, c = 17.069(3) Å, β = 115.00(3)°, Z = 4, least-square refinement of 476 parameters using 3622 reflections, R = 0.069) and (2-NCH3-21-CH3CTPP)NiIII (monoclinic, P21 /n; a = 12.946(3) Å, b = 23.519(5) Å, c = 13.945 Å; β = 93.2(3)°, Z = 4, the least-square refinement of 502 parameters using 3257 reflections, R = 0.0559) have been determined by X-ray diffraction. In the first case the nickel(II) is four-coordinate with bonds to three pyrrole nitrogen atoms (Ni−N distances 1.948(5); 1.955(5); 1.938(5) Å) and the pyrrole carbon (Ni−C 2.005(6) Å). The nickel lies in the plane of the three nitrogens, while the methylated pyrrole is sharply tilted out of the plane with dihedral angle between the plane of three nitrogens and the methylated pyrrole plane being −42.2°. The methylated pyrrole is bound to nickel via a pyramidal carbon in the η1-fashion. The first structurally characterized paramagnetic organonickel(II) complex (2-NCH3-21-CH3CTPP)NiIII presents unique features related to its electronic structure. The nickel(II) is five-coordinate with bonds to three pyrrole nitrogen atoms (Ni−N distances 2.032(8); 2.057(8); 1.979(8) Å) and to the pyrrole C(21) carbon (Ni−C 2.406(9) Å). The nickel is moved out from the plane of the three nitrogen plane toward the iodide ligand. The 21-CH3 group and iodide are located on the opposite sides of the macrocycle. The substituted pyrrole is sharply tilted out of the plane with the dihedral angle between the three nitrogen plane and the methylated pyrrole plane being −55.3°. The methylated pyrrole is bound to nickel in the η1-fashion but the coordinating C(21) atom preserves features related to trigonal sp 2 hybridization. The angle between the inverted pyrrole plane and the Ni−C bond increases from 42.8° to 70.1° on moving from the diamagnetic to paramagnetic species. The 1H NMR and 2H NMR spectra of ...

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Vertauscht man eine β‐Methineinheit und das N‐Atom eines Pyrrolrings, erhält man den neuen Porphyrinisomertyp 1, der durch Kondensation von Pyrrol und p‐Tolylaldehyd entsteht. Als vierzähniger Ligand, d. h. über die drei N‐Atome und das C‐Atom des inneren Cyclus koordiniert 1 überraschenderweise NiII‐Ionen. Das Gerüst des grünen Metalloporphyrins ist planar.magnified image

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