1,3-Diketones, metal derivatives structure

These substances [/9-diketonate metal derivatives] may be represented by formulae [/] and [III], from which it will be seen that structural isomerism... 

Complexes of 2,2 -Dialkyl( ethanediylidenedinitrilo )diethanethiols. The previously unknown Schiff base derivatives of a-diketones with -mercaptoalkyl-amines should be ideally suited to form metal complexes in which the ligand is coordinated in a planar tetradentate manner. Further, the mercaptide functions should occupy cis positions in the coordination sphere of the metal ion. Structure V illustrates the structure expected for such substances. Three products might... 

The methods of preparation and purification of metal derivatives of 1,3-diketones have been described in a previous volume. Because of the interest in the structure " and reactions of metal derivatives of /3-keto imines, RC0CH2C(=NR )R", it is desirable to consider the methods of preparation of these compounds. Inasmuch as /3-keto imines are closely related to 1,3-diketones and to salicylaldimines, o-HOC6H4CH==NR, the methods of preparation show similarities. Although this review is concerned principally with /3-keto imines, some comparisons with 1,3-diketones and salicylaldimines are made. 

The structures, types, properties, uses, nomenclature, and general methods of preparation of metal derivatives of 1,3-diketones have been discussed in a previous volume.1 It now seems desirable to consider in somewhat more detail the various factors involved in the preparation and purification of these substances. 

The family of complexes containing Schiff base ligands derived from a-diketones and /J-mercaptoethylamine [the 2,2 -dialkyl (ethanediylidenedinitrilo) -diethanethiol complexes, structure V, Ni(BE), Ni(PE), and Ni(OE)] are well designed to extend chelate ring-forming ligand reactions to their ultimate by forming complete macrocycles, that completely enclose the metal ion. The objective is shown in Equation 24. 

Despite the interest in group 2 bis(alkoxides) and bis(/3-diketonates) as precursors to metal oxides via CVD routes, systematic studies that correlate their structure and volatility still are few. The solid-state structures of many bis(alkoxides) used for CVD work are not known, and the identity of the materials may vary greatly depending on then-mode of preparation. As shown above, the widely used bis(/3-diketonate) derivative Ba(tmhd)2 for example, has that formula only if prepared under rigorously anhydrous conditions in the presence of moisture the pentanuclear cluster Ba5(tmhd)9(H20)3(OH) can form. Such uncertainties make the identification of trends in volatilities difficult. 

Homoleptic and chloro /3-diketonates have been reported for both metals. They derive from the reaction of /3-diketones (or their alkali derivatives) with either M or M halide complexes. They are generally monomeric and thus paramagnetic their structures have been proposed on the basis of UV or ESR data and less often X-ray data. 

---