Chromium(IV) siloxide.

The reaction of Na(OSi(t)Bu(2)Me) with CrCl(3) yields solid [Cr(OSi(t)Bu(2)Me)(3)](n) (1), which can be crystallized in the presence of excess Na(OSi(t)Bu(2)Me) to yield [Na(THF)][Cr(OSi(t)Bu(2)Me)(4)] (2). This complex is oxidized to yield Cr(OSi(t)Bu(2)Me)(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 (Δ(T) = 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.