Two crystalline forms of bis(2,2,-bi-2-thiazoline)bis(thiocyanato)iron(II), Fe(C6H8N2S2)2(NCS)2, were obtained. While one of them (polymorph A) shows the high-spin-low-spin transitions with a hysteresis over the temperature range ca. 170-180 K, in agreement with the literature data, the other one (polymorph B) is paramagnetic over the temperature range 77-300 K. The X-ray data are (data in parentheses refer to the polymorph B): crystal system triclinic (triclinic), space group Pi (Pi), a = 8.521 (8) A (10.846 (3) A), b = 11.063 (9) A (10.847 (3) k),c = 12.498 (6) A (12.526 (4) A), a = 96.83 (4)°(115.72 (2)°), ß = 91.81 (6)°(93.92 (2)°), 7 = 106.24 (6)°(119.97 (2)°), V= 1120 (1) A3 (1070 (1) A3), Z = 2 (2), and R = 0.0481 (0.0490). The molecules building up both crystal lattices have the cis configuration and are very similar. The single crystals of both kinds, doped with Mn(II), were investigated by electron paramagnetic resonance spectroscopy. The magnitudes of the zero-field-splitting parameters for the Mn(II) ion and the orientation of the ZFS tensor found both above and below the "crossover" temperature suggest that the spin transition does not cause major changes of the molecular symmetry. A considerable slowing down of the spin transition rate in the large single crystals with respect to the powder samples was detected by EPR. The line widths observed for the low-spin resonance observed during the spin transition in for this transition by earlier studies on powders.

A number of dithiocarbamate derivatives Ph2Te[S2CNR2I2, where R = Me, Et, and Ph2TeC1[S2CNR2], where R = Me, Et, i-Pr, have been prepared and characterized initially by analysis and vibrational spectroscopy. Three crystal structures have been completed that allow for comparisons of the effect of the change in the nature of R and of the presence of a chlorine atom. The dithiocarbamate groups are monodentate (or anisobidentate) and the geometry about tellurium is consistently that of a distorted sawhorse structure. Examples of both inter-and intra-molecular Te.. . S interactions are observed as well as an intermolecular

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