The importance of polytungstates as model compounds for homogeneous or homogeneous-heterogeneous catalysis is now well recognized, because of the triangular array of their tungsten bridging oxygens on their surfaces which resemble metal oxide surfaces. On the other hand, 183W nuclear magnetic resonance has proven to be a very good tool for determining the overall symmetry and structure of such polytungstates. Numerous efforts have been undertaken to predict a confident assignment of each tungsten line and to study the electronic changes induced on the poly tungstate anion shell in the 1-11 series by the introduction of heteroelements such as transition metals. We show that only direct proofs of the tungsten-tungsten connectivities allow an unambiguous conclusion, in contradiction with all the actually proposed methods. The direct tungsten connectivity is furnished by 2-dimensional 183W NMR on tungsten satellites (COSY and 2D INADEQUATE). The results obtained on Li7PWn039, Na7PWn039, Na8SiWn039, and Na5PPbWu039 invalidate previously published conclusions.

High-resolution xenon-129 pulsed Fourier-transform NMR studies have been carried out on a variety of 129Xe-containing compounds. New chemical shift data for this heavy nucleus in a wide range of oxidation states are summarized. The chemical shift range for 129Xe in its compounds exceeds 4000 ppm which is consistent with large paramagnetic contributions to the shielding constant. In lieu of a comprehensive theory of heavy element chemical shifts, empirical correlations among !29Xe chemical shifts are described which provide a sensitive probe for assessing the degree of ionic character in the Xe-F bond.

Durch Reaktionen der wie aufgezeigt dargestellten neutralen vierzähnigen N‐Donatorliganden (III) mit äquimolaren Mengen der Metall(I)‐Salze werden die luft‐ und wasserstabilen sowie nicht lichtempfindlichen Komplexe (IV) erhalten.

Chern. 54, 1105Chern. 54, (1976. The structure 1 (2-rnethoxy-3-bis(hydroxyrnethyl)rnethylarnin~5-hydroxy-5-hydroxyrnethyl-2-cyclohexen-1-one has been attributed to rnycosporine (P. 310), a product isolated from Stereum Iiirsutum (Willd. ex Fr.) Fr.; this result is derived from the uv, ir, ms, and nrnr of IH and 13C spectral analysis of the natural product and its derivatives.

The structure of stereoregular polymers of 1,3‐pentadiene was determined by 13C‐NMR spectroscopy at 22.6 MHz. Not only was it possible to distinguish between cis‐1,4 and trans‐1,4 but also between isotactic and syndiotactic cis‐1,4 structures. Triad effects were detected in the trans‐1,2 syndiotactic polypentadiene; 1,4–1,2 as well as 1,4–4,1 linkages were observed.