SYNTHESIS AND SPECTROSCOPIC AND ELECTROCHEMICAL CHARACTERIZATION OF IONIC AND SIGMA-BONDED ALUMINUM(III) PORPHYRINS - CRYSTAL-STRUCTURE OF METHYL(2,3,7,8,12,13,17,18-OCTAETHYLPORPHINATO)ALUMINUM(III), (OEP)AL(CH3)

The synthesis and characterization of 10 different ionic and σ-bonded aluminum(III) porphyrins are reported. These compounds were studied by mass spectrometry and IR, UV-visible, and 1H NMR spectroscopy as well as by electrochemistry. The spectroscopically investigated compounds are represented by (P)AlCl an (P)Al(R), where P is the dianion of tetraphenylporphyrin (TPP) or octaethylporphyrin (OEP) and R is CH3, n-C4H9C6H5, or C6F4H. The molecular structure of (OEP)Al(CH3) was determined by X-ray diffraction and provides the first structural data for an aluminum porphyrin complex. The Al(III) atom in (OEP)Al(CH3) is pentacoordinated and is located 0.465 (1) Å from the mean nitrogen plane. The electrochemically investigated compounds are represented by (P)AlCl and (P)Al(R), where P is OEP or TPP and R is CH3, n-C4H9, or C6H5. An overall mechanism for the oxidation and reduction of each derivative is presented, and data for the cr-bonded complexes are compared to results obtained under the same experimental conditions for oxidation and reduction of (P)M(R), where M = Ga, In, or Tl. © 1990, American Chemical Society. All rights reserved.