Stable Heterometallic Cluster Ions based on Werner's Hexol

Abstract

Large aqueous ions are interesting because they are useful in materials science (for example to generate thin films) but also because they serve as molecular models for the oxide-aqueous mineral interface where spectroscopy is difficult. Here we show that new clusters of the type M[(μ-OH)₂ Co(NH₃ )₄ ]₃ (NO₃ )₆ (M=Al, Ga) can be synthesized using Werner's century-old cluster as a substitutable framework. We substituted Group 13 metals into the hexol Co[(μ-OH)₂ Co(NH₃ )₄ ]₃⁶⁺ ion to make diamagnetic heterometallic ions. The solid-state structure of the hexol-type derivatives were determined by single-crystal XRD and NMR spectroscopy and confirmed that the solid-state structure persists in solution after dissolution into either D₂ O or [D₆ ]DMSO. Other compositions besides these diamagnetic ions can undoubtedly be made using a similar approach, which considerably expands the number of stable aqueous heteronuclear ions.

Keywords: 27Al NMR spectroscopy; aluminum clusters; aqueous geochemistry; heterometallic clusters; polyoxocations.