Stability region and methods of crystalline modification preparation of acetylacetonates and dipivaloylmethanates of tetravalent Zr, Hf, Ce, Th, U, Np and Pu

A comparative analysis of stability regions and ways of preparation of crystalline modifications of acetylacetonates and dipivaloylmethanates of a series of tetravalent metals (Zr, Hf, Ce, Th, U, Np, Pu) is carried out. During the analysis the previously published data of the present authors as well as the data of other authors have been used. Elements of similarity and difference between the families of crystalline structures M(acac)4 and M(thd)4 are found. An explanation to the considerable increase in melting temperatures of dipivaloylmethanates as compared to the corresponding acetylacetonates is suggested