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LiV2F6 crystallizes in space group P42/mnm with lattice constants a = 4.697 (3) A, c = 9.289 (3) A, and Z = 2. The structure refinement for a trirutile lattice [V at 4e, z / c = 0.33263 (8); F1 at 4f, x / a = 0.3094 (11); F2 at Sj, x / a = 0.2971 (9), z / c = 0.3277 (3)] gave R = 5.0% for 371 reflections and showed two edge-sharing distorted VF, octahedra and a single V site. The compound is truly mixed-valent. The distortions of the VF6 octahedra and the inferred reordering of VI1 and VI1' energy levels help to explain the temperature-dependent magnetic susceptibility of LiV2F6 (which has been remeasured). Madelung energies are also reported.

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a low-symmetry environment such as that of the protein blue sites, it is known from model studies31,67 that an increase in the size of the fused chelate rings can lead to a significant distortion of the metal geometry. Thus, it is expected that ligand homologues of pyt-N,S-im containing longer carbon chains between the donor atoms will give rise to copper(II) complexes that progressively approach the spectral behavior of the blue sites. The synthesis of such ligand systems is currently under way in this laboratory. Finally, while the attention is usually focused only on the spectral properties of copper(II) model systems, it is important to give parallel development to the characterization of the corresponding copper(I) systems, even though they generally exhibit poor spectral properties. We have shown in this and in previous studies50,51c that careful examination of the solution behavior of copper(I) complexes can give useful information about the groups involved in metal binding.Acknowledgment This work was supported by a grant from the Italian MPI. I thank the Italian CNR for instrumentation facilities, M. Bonfá for recording the NMR spectra, P. Russo for recording the MS spectra, and C. Pessina for assistance in the synthesis of 1 -phenyl-3-formyl-2( 1 //)-pyridinethione. Registry No. I, 61856-49-3; III, 91002-69-6; [IV] [C104] ( = Cu(I)), 91002-60-7; [IV][C104]2 (M = Cu(II)), 91002-62-9; [I-V][C104]2 (M = Zn(II)), 91002-64-1; [V][C104], 91002-66-3; [VI] [C104]2, 91002-68-5; 4-|[(2-aminoethyl)thio]methyl]-5-methylimidazole, 38585-67-0.