Synthesis and properties of bis(t-butyl)methoxides of chromium(III,IV), manganese(II), iron(III), cobalt(II), and copper(I). The crystal and molecular structures of lithium tetrakis[bis(t-butyl)methoxo]chromate(III)–tetrahydrofuran (1/1), tetrakis[bis(t-butyl)methoxo]chromium(IV), and lithium tetrakis[bis(t-butyl)methoxo]ferrate(III)–bis(t-butyl)-methanol (1/1)

Abstract

By the interaction either of transition-metal dialkylamides with bis(t-butyl)methanol or of the halide with the lithium alkoxide, a series of neutral alkoxides or lithium alkoxo-metallate anions have been prepared for chromium(III,IV), manganese(II), iron(III), cobalt(II), and copper(I). Electron paramagnetic resonance and electronic absorption spectra are reported. The crystal and molecular structures of the complexes LiCr(OCHBu^t₂)₄·thf(1), Cr(OCHBu^t₂)₄(2), and LiFe(OCHBu^t₂)₄·Bu^t₂CHOH (3) have been determined by an X-ray crystallographic study. Compound (1) is triclinic, space group P, with a= 19.986(2), b= 11.618(2), c= 11.390(1)Å, α= 117.61(1), β= 76.45(1), γ= 93.11(1)°, and Z= 2. Compound (2) is monoclinic, space group C2/c, with a= 20.249(3), b= 10.748(1), c= 20.275(2)Å, β= 116.68(1)°, and Z= 4. Compound (3) is monoclinic, space group P2₁/n, with a= 18.308(3), b= 22.505(4), c= 11.979(5)Å, β= 94.20(1)°, and Z= 4. The structures were determined using data measured on an automatic diffractometer and refined by least squares to R values of 0.068 (3 396 observed data), 0.067 (2 057 data), and 0.061 (4 879 data) for (1), (2), and (3) respectively. All structures contain a distorted tetrahedrally co-ordinated Cr or Fe atom; and in (1) and (3), the lithium ion is incorporated into the MO₄ co-ordination sphere, and bridges two of the four alkoxo-oxygen atoms. The transition-metal geometries are discussed in terms of steric electronic factors.