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Studies have been carried out on two solvent-dependent structures of Co(NO 3 ) 2 with trans-1,2-bis(4-pyridyl)ethylene (bpee) and their interconversions. X-ray analyses disclose that the molecule obtained in MeOH/CHCl 3 is an infinite ladder structure, [Co(NO 3 ) 2 (bpee) 1.5 ‚3CHCl 3 ] n (triclinic P1 h; a ) 10.415(4) Å, b ) 13.425(4) Å, cFor [Co(NO 3 ) 2 (bpee) 1.5 ‚ 3CHCl 3 ] n , the local geometry around the cobalt(II) atom approximates to a heptacoordinate environment with four oxygens and three nitrogens. The four oxygen sites are occupied by an isobidentate and an anisobidetate nitrate ligand. Each bpee spacer connects two cobalt(II) atoms defining a T-shaped arrangement at the metal atom. For [Co(H 2 O) 4 (bpee) 2 ](NO 3 ) 2 ‚ 8 / 3 H 2 O‚ 2 / 3 bpee, the cobalt atom is in a typical octahedral arrangement with two bpee ligands and four water molecules. The bpee ligand is coordinated to the cobalt atom in a monodentate mode with a dangling pyridine group. Thermal and IR analyses of the present two complexes show that in the solid state the mononuclear complex is changed to the ladder structure at temperatures above 150 °C. Moreover, the ladder structure slowly shifts to the mononuclear complexes at sufficient moisture condition. Thus, either the ladder structure or the mononuclear complex exists depending on the presence or absence of moisture.

A study of striking structural differences in the magic angle of Py2S and coligand effects has been carried out. [Co(Py2S)2Cl2] n is the first integral two-layer interwoven sheet without any counterion or solvate whereas [Co(Py2S)2(NCS)2] n affords a double-stranded linear infinite structure. Thermal analyses of the complexes over the temperature range 25−430 °C show the significant thermal behaviors associated with the structure.

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All the possible three O,O‘-, O,S-, and S,S‘-chelation modes were observed for diamineplatinum(II) complexes of sulfur-containing dicarboxylate ligands S−(CH2) n −S−CC(COO-)2 (n = 2, 3, 4) depending on their dithioether ring size. Such variable coordination modes are explicable in terms of their ring size effects affording different degrees of contribution to the resonance structures of the planar C2CCS2 moiety, which gives rise to dramatic change in the basicity of the ring sulfur atoms competing with the carboxylate oxygen atoms for coordination to patinum(II).

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