Butyltin Keggin Ion with a Rare Four-Coordinate Ca Center

Published on 2020-02-14T15:12:32Z (GMT) by
Alkyltin clusters are exploited in nanolithography for the fabrication of microelectronics. The alkyltin Keggin family is unique among Keggin clusters across the periodic table; its members appear to favor the lower-symmetry β and γ isomers rather than the highly symmetrical α and ε isomers. Therefore, the alkyltin Keggin family may provide important fundamental information about the formation and isomerization of Keggin clusters. We have synthesized and structurally characterized a new butyltin Keggin cluster with a tetrahedral Ca<sup>2+</sup> center, fully formulated [(BuSn)<sub>12</sub>(CaO<sub>4</sub>)­(OCH<sub>3</sub>)<sub>12</sub>(O)<sub>4</sub>(OH)<sub>8</sub>]<sup>2+</sup> (β-CaSn<sub>12</sub>). The synthesis is a simple one-step process. Extensive solution characterization including electrospray ionization mass spectrometry, small-angle X-ray scattering, and multinuclear (<sup>1</sup>H, <sup>13</sup>C, and <sup>119</sup>Sn) nuclear magnetic resonance shows β-CaSn<sub>12</sub> is essentially phase-pure and stable. This differs from the previously reported Na-centered analogues that always form a mixture of β and γ isomers, with facile interconversion. Therefore, this study has clarified prior confusion over complex spectroscopic and crystallographic characterization of the Na-centered analogues. Density functional theory calculations showed the following stability order: γ-CaSn<sub>12</sub> < γ-NaSn<sub>12</sub> < β-CaSn<sub>12</sub> < β-NaSn<sub>12</sub>. The β analogue is always more stable than the γ analogue, consistent with experiment. Notable outcomes of this study include a rare tetrahedral Ca coordination, a Na-free alkyltin cluster (important for microelectronics manufacturing), and a better understanding of Keggin families built of different metal cations.

Cite this collection

Hutchison, Danielle

C.; Stern, Rebecca D.; Zakharov, Lev N.; Persson, Kristin A.; Nyman, May (2020): Butyltin Keggin Ion with a Rare Four-Coordinate Ca

Center. ACS Publications. Collection. https://doi.org/10.1021/acs.inorgchem.9b03261