Chromium(IV) Siloxide

The reaction of Na­(OSitBu2Me) with CrCl3 yields solid [Cr­(OSitBu2Me)3]n (1), which can be crystallized in the presence of excess Na­(OSitBu2Me) to yield [Na­(THF)]­[Cr­(OSitBu2Me)4] (2). This complex is oxidized to yield Cr­(OSitBu2Me)4 (3), a crystalline chromium­(IV) siloxide complex that is air- and moisture-stable. Electronic spectroscopic analysis of the absorption spectrum of 3 indicates a particularly weak ligand field (ΔT = 7940 cm–1) and covalent Cr–O bonding. 3 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.