253ChemInform Abstract If the reaction, which leads to CuS (covellite) at reflux temp., is carried out at 25 rc C a crystalline solid is obtained, which is identified as (IV) ( P21/n, Z=4). (IV) is an unusual example of a charge-neutral metal polysulfide complex shown to undergo ligand substitution reactions. For example, the pyridine ligand are exchanged with N-methylimidazole in Et2O reversibly.

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N‐Methylimidazole suspensions of zinc exhibit particularly well behaved reactivity toward sulfur yielding the hexasulfide (III) (space group P1, Z=2).

and results of data collection and refinement, bond distances, bond angles, and anisotropic displacement parameters for 2, 4, and 8 and a table of positional and thermal parameters and ORTEP drawings for 4 (35 pages); tables of observed and calculated structure factors (77 pages). Ordering information is given on any current masthead page.

We have obtained ' 0 nuclear-magnetic-resonance spectra of powder samples of YBa2Cu307and EuBa2Cu30& -, as well as magnetically ordered YBa2Cu307-". Two major features are observed in YBa2Cu307 -. 'a sharp resonance at =1800 ppm (from external H2' 0, International Union of Pure and Applied Chemistry 8 scale) and a broader series of features centered at =400 ppm. The 1800-ppm feature undergoes a diamagnetic shift of =800 ppm on cooling to 77 K, and a similar magnitude shift on Eu substitution, suggesting assignment to the plane oxygens, O(2, 3). Measurements on magnetically ordered samples at 8.45 and 11. 7 T give the magnitude of the diagonal terms of the electric-field-gradient tensor, which are 2.3, 3.5, and 5.8 MHz. For the column oxygen, O(1), we find e q2g/h 7.7 MHz, with a chemical shift anisotropy of =660 ppm.All of the new high-T, superconducting oxides' are, in principle, excellent candidates for study using ' 0 nuclear-magnetic-resonance (NMR) spectroscopy. We show in this Rapid Communication that such studies are indeed possible, and by using magnetically aligned materials, ' we are able to investigate both chain and plane sites in ' 0-labeled YBa2Cu307 . We observe large changes in the ' 0 resonance frequency shifts (of the plane oxygens) upon formation of the superconducting state. Additionally, we have determined the nuclear quadrupole coupling constants (e qQ/h), electric-field-gradient tensor asymmetry parameters (rl), and chemical shift anisotropies (t5, 8) for selected oxygen sites. Given the ubiquitous nature of oxygen in high-T, superconductors, such atomic level probes of both magnetism and structure oN'er considerable hope for elucidating the details of superconductivity in these systems. Unlabeled YBa2Cu307 -, (and EuBa2Cu 307 -") was prepared from Y203(Eu203), BaCO3, and CuO (99.99%,