Structural and thermal studies on hydrazinum (1+) metal sulfate and oxalate complexes

Abstract

Coordination compounds of hydrazine are of particular interest because of the variety of ways in which hydrazine can be coordinated to the metal ion. Apart from its ability to function as a monodentate ligand, another possibility is that the two nitrogen atoms, while being incapable of bonding to the same metal through steric and symmetry considerations, may coordinate to two different metal atoms, thus forming polymeric chains with hydrazine bridges. The monoprotonated hydrazinium cation, N?H??, possesses a basic site and should be capable of coordination. Although postulated in certain cases, not many compounds are known—except for N?H?CuCl? and (N?H?)?Zn(SO?)?, where the N?H?? ion is coordinated to the metal. From a survey of literature, it is seen that although extensive work has been done on neutral hydrazine metal complexes and hydrazinium metal halides, not much is known about hydrazinium metal sulphates and oxalates. The present investigation aims at synthesis, characterisation, and thermal properties of hydrazinium metal sulphate and oxalate complexes, and also at studying the nature of coordination of the N?H?? ion with various metal ions, including rare earths and actinides, using spectroscopic and X?ray crystallographic techniques. Thermal analysis and structural studies of simple and complex hydrazinium compounds are presented in the introductory chapter. The scope and objectives of the present investigation are highlighted.

Chapter II This chapter describes the analytical procedures and instrumental methods employed in the study. The instrumental methods used are differential thermal analysis (DTA), thermogravimetry (TG), magnetic susceptibility measurements, infrared, electronic, and Mössbauer spectroscopy, along with single?crystal and powder X?ray diffraction studies.

Chapter III This chapter discusses the preparation, characterisation, and thermal analyses of hydrazinium (1+) lithium, magnesium, and aluminium sulphates as representatives of Groups I, II, and III respectively. The preparation of (N?H?)Al(SO?)? was attempted by three different methods in an effort to obtain single crystals. However, the crystals obtained were unsuitable for structural studies.

Chapter IV This chapter reports the preparation and thermal decomposition of:

(N?H?)?M(SO?)?·3N?H? where M = Fe, Co, Ni, Zn or Cd (N?H?)?M(SO?)? where M = Mn, Fe, Co, Ni, Cd, Cu, Zn, and Cd

The compositions of intermediates and decomposition products are of interest. All the complexes decompose exothermically to give MSO? or a mixture of MSO? and MS.

Chapter V This chapter describes the synthesis, characterisation, and thermal properties of N?H?Ln(SO?)?·H?O, where Ln = La, Ce, Pr, Nd and Sm. The crystal structure of N?H?Nd(SO?)?·H?O is reported. The structure was solved by the heavy?atom method and refined by full?matrix least?squares procedures. The structure is polymeric, with two crystallographically independent neodymium atoms in the asymmetric unit having similar coordination. The N?H?? ions and water molecules are coordinated to the metal, and the sulphate groups act as bridging ligands. The coordination number is nine, with a tricapped trigonal prismatic coordination polyhedron. Powder patterns of La, Ce, Pr and Sm analogues reveal that they are isomorphous with the Nd compound. X?ray data are supplemented by IR, visible spectra, and magnetic susceptibility measurements.

Chapter VI This chapter presents the synthesis and characterisation of (N?H?)?M(C?O?)?·nH?O, where M = Co, Ni, Cu and n = 3, 2, 1 respectively. Although these compounds were previously reported from our laboratory, no crystallographic work had been undertaken. The crystal structure of (N?H?)?Cu(C?O?)?·H?O is presented. The structure was solved using the heavy?atom method and refined by full?matrix least?squares procedures. Copper exhibits square?planar geometry. The oxalate groups are bidentate (chelating), and the N?H?? ions and water molecules are not coordinated to the metal, though they are involved in hydrogen bonding with oxalate oxygens.

Chapter VII The preparation and crystal structure of N?H??·2H?O is described. The structure was solved by the heavy?atom method and refined by least?squares procedures. The crystal contains UO?²? ions coordinated by two chelating oxalate groups; one oxalate group also acts as a bridging bidentate ligand. The coordination geometry around uranium is approximately pentagonal bipyramidal. X?ray data are supplemented by IR, visible spectra, and thermal data.

Conclusion The concluding part discusses the nature of coordination of the N?H?? ion with various metal ions and the mode of decomposition of the complexes.