Zirconium compounds accessibility

Bis(phthalocyanines) are also accessible by the reaction of isoindolinediimine and suitable metal compounds. For example, zirconium(IV) chloride when treated with isoindolinediimine in refluxing quinoline under a nitrogen atmosphere for 2 hours gives a zirconium(IV) bis(phthalocyanine) complex. 

Metal rf-inline complexes with various transition metals [1-10] and lanthanides [11,12] are well known in the literature. Early transition metal if-imine complexes have attracted attention as a-amino carbanion equivalents. Zirconium rf-imine complexes, or zirconaaziridines (the names describe different resonance structures), are readily accessible and have been applied in organic synthesis in view of the umpolung [13] of their carbons whereas imines readily react with nucleophiles, zirconaaziridines undergo the insertion of electrophilic reagents. Accessible compounds include heterocycles and nitrogen-containing products such as allylic amines, diamines, amino alcohols, amino amides, amino am-idines, and amino acid esters. Asymmetric syntheses of allylic amines and a-amino acid esters have even been carried out. The mechanism of such transformations has implications not only for imine complexes, but also for the related aldehyde and ketone complexes [14-16]. The synthesis and properties of zirconaaziridines and their applications toward organic transformations will be discussed in this chapter. 

Homologation-condensation. 3-Acyltetramic acids are accessible from N-acylacetylglycine esters. In turn the latter compounds may be assembled from a-diazo acetamide derivatives and aldehydes with elimination of dinitrogen. Zirconium chloride is a useful catalyst. 

In the case of zirconium and hafnium the lack of accessible dichlorides means that alkyl derivatives are generated via the corresponding homoleptic alkyl intermediates. With bulky 2,6-di-ferf-butylphenoxide the tris-benzyls [(ArO)ZrR3] can be isolated and studied. " The dialkyls [(ArO)2MR2] (M = Zr, Hf R = Me, benzyl) can also be isolated for bulky aryloxides. In the case of 2,6-diphenylphenols the monomethyl species [(ArO)3ZrMe] are readily formed by simple addition of parent phenol to the dimethyl compound. 

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