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The crystal structure of the title compound, [CO(C15H11N3)2](ClO4)2.c. 1.3H2O has been determined by single crystal X-ray diffraction methods at 295 K. The structure is described in terms of atetragonal P42/n sub-lattice structure similar to that of [Co(terpy)2]I2.2H2O, with a 8.86(1), c 20.19(2) �. Perchlorate orientation and disorder, however, demand consideration of superlattice structures in I 41/a//F41/d with 4 and 8 times the P41/n cell volume. The relationship between the general structural features of the [Co(terpy)2] X2 salts is described and discussed. The cobalt-nitrogen(central, distal) distances (2.03, 2.14 �) are the longest observed in the [Co(terpy)2]2+ system, and are consistent with the unusually high magnetic moment of the salt (4.2 BM).

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Structural parameters derived from 9(1)K X-ray diffraction data and 13(1)K time-of-flight neutron diffraction data on perdeuterated tetraamminedinitronickel(II), Ni(ND3)4(NO2)2, are compared. It is shown that excellent agreement can be obtained for both positional and thermal parameters derived separately from the two experiments, provided that great care is taken in all steps of the process, including data collection, data reduction, and nuclear and electronic structure refinement. The mean difference in the thermal parameters, , is as low as 0.00034/~ 2 and <(AUij/cr)2> I/2 = 1.92, showing that, even without any form of scaling between the parameters, the same values can be obtained. This, compared with other such studies, indicates that time-of-flight neutron diffraction data can give structural information of a quality comparable to monochromatic neutron diffraction. The excellent correspondence between the thermal parameters derived separately from X-ray and neutron diffraction data gives confidence in the deconvolution of the thermal motion from the X-ray diffraction data, which is necessary for any study of a static electron density distribution.