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ScopeAmong the primary tasks of catalysis is the control of the selectivity in chemical reactions. In heterogeneously catalyzed reactions in zeolites and zeolite-related microporous solids, this can, inter alia, be achieved by exploiting the phenomenon of shape-selective catalysis. In a very simplified manner, shape-selective catalysis can be described as the combination of catalysis with the molecular sieve effect. Shape selectivity effects can occur, if the sizes and shapes of reactants, of products, of transition states or of reaction intermediates are similar to the dimensions of the pores and cavities of the zeolite.The first examples of shape-selective catalysis in zeolites were reported more than 35 years ago by Weisz and Frilette from the Mobil laboratories [1,2]. Since those days, research in the field of shape-selective catalysis has expanded both at universities and in industrial laboratories in an impressive manner. This has resulted in numerous examples of shape selectivity effects in the course of catalytic conversions over zeoli tic catalysts, which are nowadays no longer restricted to acid-catalyzed reactions as described in the early days. Rather, there are also examples for shape-selective catalysis on metals, on redox active sites, on basic guests in zeolites, and even for shape-selective photochemistry in a zeoli tic environment. Moreover, from the intensive research done in the field of shapeselective catalysis during the last decades, several large-scale commercial applications in the refining and the petrochemical industries have emerged, demonstrating the usefulness and importance of the phenomenon of shape-selective catalysis.In the past, numerous review papers on shape-selective catalysis, its principles and its commercial applications have been published [e. g., 3 -19]. In view of the vast amount of work that has been done in this field in recent years, it is obvious that a review on shape-selective catalysis cannot be exhaustive. Rather, the discussion has to be restricted to selected topics. In the present contribution, emphasis will be placed on a thorough discussion of the classical and of more recent principles of shape-selective catalysis and on how these principles can be used to rationalize the observed catalytic behavior in selected examples. In addition, it is the aim of the present contribution to discuss the available methods for tailoring the shape-selective properties of zeolite catalysts and for their characterization by catalytic methods. Finally, an attempt will be under-

Die Metall-acetylacetonate M(acac)z (M = Mg, Co, Ni, Cu, Zn), M(acac)3 (M = Al, Sc, V, Cr, Mo, Mn, Fe, Co, In, Ce), MO(acac)2 (M = Ti, V), MoOz(acac)z und M(acac)4 (M = Zr, Th) werden mit Octaathylporphin [ l ; (OAP)Hz] umgesetzt (Tabb. 1 und 2). Abgesehen von Komplexen der Metalle Ce und Th werden die Octathylporphin-Chelate 2-5 (Tab. 3) erhalten. Als gunstigstes Losungsmittel fur die Umsetzungen hat sich Phenol erwiesen : diesem ist Imidazol nur im Falle des Sc(acac)3 wegen der Saurelabilitat der bisher nicht beschriebenen Scandiumkomplexe 3g und 5 uberlegen. Aus Mo(acac), wird Octaathylporphinatomolybdan(1V)-oxid [4c; (OAP)MoO] gewonnen. Ausgehend von Zr(acac)4 erhalt man Octaathylporphinato-zirkon-diacetat [2 i ; (OAP)Zr(OAc)z]. Metal Complexes with Tetrapyrrole Ligands, III l a ) . Preparation of Metal Complexes of Octaethylporphin from Metal Acetylacetonates Octaethylporphin [l; (OAP)Hz] is treated (tables 1 and 2) with the metal acetylacetonates M(acac)z (M = Mg, Co, Ni, Cu, Zn), M(acac)3 (M = Al, Sc, V, Cr, Mo, Mn, Fe, Co, In, Ce), MO(acac)z (M = Ti, V), MoOz(acac)z and M(acac)4 (M = Zr, Th). With the exception of Ce-and Th-complexes the metalloporphyrins 2-5 have been obtained (table 3). Phenol has been found to be the best solvent for the reactions described. Only in the case of Sc(acac)3, imidazole is more useful because the hitherto unreported scandium complexes 3g and 5 are very labile towards acids. Mo(acac)3 yields octaethylporphinato-molybdenum(1v)-oxide [4c ;(OAP)MoO]. Starting from Zr(acac)4, octaethylporphinato-zirconium-diacetate [2i;(OAP)Zr(OAc)z] is obtained.

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(1 and Niz@ ions, respectively, in the same solvent. 9 is dehydrogenated by molecular oxygen in glacial acetic acid to yield g,y-dimethyl-octaethylporphin (0DM)Hz 10, which is further characterized by preparation of the metal chelates (0DM)Cu 11 b and (0DM)Ni l l c . The constitution of the products is proved by mass spectra (table l), IHresonance spectra (tables 2 and 3) and electronic spectra. The new tetrapyrrole pigments are compared with the known porphins as well as the meso unsubstituted a,y-dihydroporphins and the influence OF the central metal on the course of the reductive methylation is discussed. 912 (1969).