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The syntheses, crystal structures, and magnetic susceptibilities of a family of copper pyrazine (pz)-based antiferromagnets with moderate in-plane magnetic exchange is reported. The compounds are well described by the two-dimensional Heisenberg model over most of the temperature range but undergo transition to an ordered state at low temperature.

The theoretical and crystallographic methods were used to investigate the two types of halogen...halide synthons. The findings have suggested that halogen...halide interactions are controlled by electrostatics and are characterized by linear C-Y...[X.sup.-] angles and separation distances less than the sum of van der Waals radius of the halogen atom and the ionic radii of the halide anion.

Research has been conducted on the design of the low dimensional coordination polymers containing Cu(I) and Cu(II) halides. The reaction of the copper(II) halides with 2,3-dimethylquinoxaline has been examined in obtaining the systems analogous to the pyrazine complexes but with the additional bulk of the dmq ligand and the results are presented.

Research explores the crystal chemistry of the interaction of an organic ligand with copper halides. Data indicate that copper(II)/dimethylbipyridine complexes are more stable than the corresponding complexes with copper(I) and copper(II) sources are the trigonal bipyramidal copper(dmbp)(sub)2bromide(sup)+ cation and the copper(dmbp)bromide complex.

Three crystalline copper(I) bromide salts, containing brominated anilinium cations, are prepared by protracted reaction between 3-chloroaniline with copper bromide in hydrogen bromide solution. One of the three compounds exhibits an unique two-dimensional lattice formed by corner shared Cu(sub)2Br(sub)2 species.

Crystallographic analyses were utilized to investigate the structure and the magnetic properties of a novel member of the A2CuX4 series (A = dication of 3-aminopicoline). Due to the unique structural characteristics of the 3-picolylamine dication, hydrogen bonding can occur between the cations and the halide atoms. The hydrogen stabilization of the structure determined the highly distorted framework.

The complex (dabcoH2)2Cl3[CuCl3(H2O)2].H2O is a low-symmetry five-coordinated copper compound with Cu(II) unit exhibits a trigonal bipyramidal geometry. The distances of the Cu-Cl bond is 2.375 angstrom and the bond distance of Cu-N is 2.118 angstrom. The distorted trigonal bipyramidal geometry of the Cu(II) is composed of three Cl atoms that are located on the equatorial planes and two H2O units in the axial position. A 'negative' epsilon prime distortion characterizes the geometry of the [CuCl3(H2O)2]- anion.

The crystal structure of (3-chloroanilinium)(sub 8) NiCl10 has been found after synthesis. The NiCl(sub 6)(super 4-) anion has axial lattice strain leading to compression. The copper form of this crystal is also analyzed from x-ray diffraction study and two models. Cu-Cl bond lengths are found by combining lattice strain and Jahn-Teller distortion.

Reaction of triorganotin chlorides with Li(2,4,6-(CF3)3C6H2) or (LiOC(CF3)2)2C6F4 produces triorganotin(IV) derivatives of 1,4-bis(perfluoroisopropoxy)tetrafluorobenzene and 2,4, 6-tris(trifluoromethyl)benzene. Single crystal X-ray studies reveal the presence of Sn-F contacts in the solid state, while 19F NMR studies do not support the presence of Sn-F bonding interactions. 119Sn NMR spectroscopy helps analyze the tin-fluorine interactions in the derivatives.

The complexes RuIIICp(CPD)(CH3CN)+ and RuIICp(CPD)2(super 2+), where CPD = 2,4-cyclopentadiene-1-one were prepared and used as precursors to nucleophilic attack reactions. These complexes react with nucleophiles such as nitriles, pyridine, halides, thiourea, 4, 4-bipyridine, isocyanides and thioethers to yield mononuclear products of the form, RuIIICp(CPD)(nucleophile). The 1H and 13C NMR spectra of the products showed similar patterns for all the RuCp(CPD)+ moieties. The structure of the PF6- crystals of the Ru complexes are also discussed.

Solidification of tert-butyl(N,N-dimethylamino)carbodiimide, a liquid carbodiimide, results in two dimeric inner salts. Spectroscopic analysis of the two products reveals coupled C double bond N absorption, dimethylamino protons and tert-butyl methyl protons. A molecular ion at m e 282 exists in the mass spectra of one of the dimers. Demethylation of this dimer is possible and this dimer reacts with picric acid to form the expected picrate derivative.

Magnetic interactions in homometallic chains M(4-cyanopyridine)2Cl2, M=Cu,Ni,Co were investigated using chemical and powder x-ray analysis. The results showed that the compounds form an isostructural series. The susceptibility product initially increased rapidly and reached a peak of 5.6 cgs K/mol near 2.6 K, then decreased to zero. The maximum of the magnetic susceptibility was observed at a temperature of 2. 4 K.

The crystal structures of [[[(n-[C.sub.4][H.sub.9]).sub.2]].sub.2][Cd.sub.9][Cl.sub.20].2[H.sub.2]O and [[Cu([C.sub.14][H.sub.24][N.sub.4])].sub.2][Cu.sub.13][Cl.sub.30][([H.sub.2]O).sub.2].x[H.sub.2]O compounds, containing perforated layer structures are studied. The water molecules are found to be hydrogen bonded to chloride ions on both sides of excision.

The room-temperature crystal structure of Dimethylammonium trichlorocuprate consisting of a linear chain of [Cu.sup.2+] dimers with unusual magnetic properties is presented. The reported structure has solved the confusion regarding the origins of the magnetic behavior of the compound and gives a convincing example of the importance of two-halide magnetic exchange.

Research has been conducted on organoammonium metal halide salts. The crystal structures of these salts have been determined, and the results demonstrate that this is the first example of the polytypic structures based on recombination and dimensional reduction of the hexagonal MX (sub)2 structure type.

The structure of two isomorphs of the title compound is reported. The two phases can be cocrystallized from solution at room temperature and also in addition no disorder of the organic cation is observed in either phase.