Silicon-29 NMR Structural Characterization of Two Novel Germanosilicate Cages in a Tetramethylammonium Germanosilicate Solution

C. T.G. Knight, Eric Oldfield, R. James Kirkpatrick

Research output: Contribution to journalArticle

Abstract

We have identified two novel germanium-substituted silicate cages in an aqueous tetramethylammonium germanosilicate solution by means of high-field (11.7 T) silicon-29 NMR spectroscopy, with 29Si isotopic enrichment. Our results indicate that these anions exist in the form of a double four-membered ring (cubic octameric cage) and a double three-membered ring (prismatic hexameric cage), in which a single silicon site is replaced by germanium. Introduction of chemical shift nonequivalence by means of heteroatom incorporation leads to complex spin-spin splitting patterns, which may, however, be readily interpreted by means of two-dimensional homonuclear correlated spectroscopy (2D-COSY) or by spectral simulation. The 2J couplings are 7.5 Hz in the double four-membered ring and 4.3 Hz in the double three-membered ring. A 4J coupling of ~ 1.0 Hz is also deduced for the double three-membered ring. These results represent the first solution NMR observation of heteroatom incorporation into silicate cages and provide a novel means for investigating the structures and stabilities of such species.

Original languageEnglish (US)
Pages (from-to)30-33
Number of pages4
JournalJournal of the American Chemical Society
Volume108
Issue number1
DOIs
StatePublished - Jan 1 1986

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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