ic9b03261_si_001.pdf (1.04 MB)
Butyltin Keggin Ion with a Rare Four-Coordinate Ca Center
journal contribution
posted on 2020-02-14, 15:12 authored by Danielle
C. Hutchison, Rebecca D. Stern, Lev N. Zakharov, Kristin A. Persson, May NymanAlkyltin
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 Ca2+ center, fully formulated [(BuSn)12(CaO4)(OCH3)12(O)4(OH)8]2+ (β-CaSn12). The synthesis is a simple one-step
process. Extensive solution characterization including electrospray
ionization mass spectrometry, small-angle X-ray scattering, and multinuclear
(1H, 13C, and 119Sn) nuclear magnetic
resonance shows β-CaSn12 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-CaSn12 <
γ-NaSn12 < β-CaSn12 < β-NaSn12. 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.