Warfarin in solution is shown to consist of three interconverting tautomeric structures, two of which are cyclic diastereomeric hemiketals, while the third and minor component is the open-chain intermediate form. The configurations of all the tautomers as well as the major conformations of the cyclic tautomers are assigned. The assignments are supported by comparison with the chemical shift and coupling constant parameters of structurally fixed model compounds.

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Further refinement of the crystal structure of Cs2CuCl4 and a partial analysis of the crystal structure of [N(CH3)4]2CuCI4 have been carried out. The bond angles in the distorted tetrahedral configuration of CuCl4are 124.9, 123.3, 102.5 and 102.9°, all ±0.7°.

The crystal structures of the isomorphous tetramethylammonium tetrachloro-cobaltate(II), -nickelate(II), and -zincate(II) are reported. The space group is Pnma with Z= 4. The cell dimensions are a= 12.276, b=9-001, c=15.539/~ for the cobalt isomorph; a=12-264, b=8.982, c=15"486/~ for the nickcJ isomorph; and a= 12.276. b= 8.998, c= 15.541/~ for the zinc isomorph. The structures were determined from three-dimensional X-ray diffraction data and were refined bythe full-matrix least-squares technique. There is some disordering in the orientation of both the [MCI4] 2-and the [N(CH3)4] + tetrahedra. The [MCI4] 2-tetrahedron appears to be disordered in the same manner in the three compounds. TETRAMETHYLAMMONIUM

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