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).

The crystal structure of the title compound, [CO(C15H11N3)2] 12.2H2O, has been determined by single crystal X-ray diffraction methods at 295 K and at 120 K, being refined by least squares to residuals of 0.051 and 0.035 respectively for 982 and 1024 'observed' reflections at these temperatures. Both structures are based on a P42/n tetragonal cell, a c. 8.9, c c. 19.4 �, Z 2, in which only a quarter of the cation is independent, being located about a site of 4 symmetry. At room temperature (μoff c. 3.2 BM) Co-N (central, distal) are 1.942(7), 2.104(5) � diminishing to 1.912(5), 2.083(4) � at 120 K, with μoff c. 2.2 BM, corresponding to a fully populated low-spin ground state.

The crystal structures of (ND4)2V(SO4)2.6D2O and (ND4)2V0.45Zn0.55(SO4)2.6D2O have been determined at 5.8 K by neutron diffraction. The 663 and 857 unique reflections measured respectively refined to give R(F2) 0.035 and 0.045. The crystals are monoclinic, P21/a, isostructural with the other members of the series of Tutton salts. The V-O bond length of 211.8 pm [210.4 pm for mean (V/Zn)-O in the solid solution with Zn] is intermediate between these for the Mn (214.9 pm) and the Ni(205.5 pm) salts. It is shorter than the value determined by X-ray diffraction at 295 K. The major departure from a regular VO6 octahedron is a shortened V-O(9) bond, such as is observed in the other Tutton salts, to give a tetragonal distortion.

The crystal structure of the title compound [Fe(mphen)3] (BPh4)2 a high-spin derivative of iron(II), has been determined by a single crystal X-ray diffraction study at 295 K, being refined to a residual of 0.055 for 4079 'observed' reflections. Crystals are monoclinic P 21/c, a 12.326(8), b 15.387(8), c 3679(3) �, β 98.80(6)�, Z 4. The metal atom environment is considerably distorted from ideal D3 point symmetry; Fe-N distances range from 2.143(5) to 2.294(4)�.

The crystal structure of the title compound, [Fe((C5H4N)3N)2] (ClO4)2, has been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to a residual of 0.059 (1995 'observed' reflections). Crystals are monoclinic, P21/a, a 12.815(4), b 17.503(7), c 8.318(3) Ǻ, β 121.38(3)°, Z 2. The complex cation lies with the metal atom on a centre of symmetry, the metal being six-coordinate, so that only one of the tridentate ligands is crystallographically independent. The geometry about the metal atom deviates only trivially from octahedral, <N-Fe-N> within the one ligand being 88.1°. <Fe-N> is 1.982 Ǻ.