Chromium(IV) Siloxide
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Abstract
The reaction of Na(OSi<sup>t</sup>Bu<sub>2</sub>Me) with
CrCl<sub>3</sub> yields solid [Cr(OSi<sup>t</sup>Bu<sub>2</sub>Me)<sub>3</sub>]<sub><i>n</i></sub> (<b>1</b>), which can
be crystallized in the presence of excess Na(OSi<sup>t</sup>Bu<sub>2</sub>Me) to yield [Na(THF)][Cr(OSi<sup>t</sup>Bu<sub>2</sub>Me)<sub>4</sub>] (<b>2</b>). This complex is oxidized to yield Cr(OSi<sup>t</sup>Bu<sub>2</sub>Me)<sub>4</sub> (<b>3</b>), a crystalline
chromium(IV) siloxide complex that is air- and moisture-stable. Electronic
spectroscopic analysis of the absorption spectrum of <b>3</b> indicates a particularly weak ligand field (Δ<sub>T</sub> =
7940 cm<sup>–1</sup>) and covalent Cr–O bonding. <b>3</b> provides the first structural and spectroscopic characterization
of a homoleptic chromium(IV) siloxide complex and provides a benchmark
for tetrahedral chromium(IV) ions residing in solid oxide lattices
