A series of Mn(II), Fe(II), and Co(II) bisaryloxide dimers
([M(OC6H2-2,4,6-Cy3)2]2{M = Mn (1), Fe (2), and Co (3)} were synthesized by the addition of 2,4,6-tricyclohexylphenol
(HOC6H2-2,4,6-Cy3) to the silyl amido
dimers [M(N(SiMe3)2)2]2(M = Mn, Fe, Co; Cy = cyclohexyl). An unexpected and unique Co(II)
phenoxide derivative (4), [Co(OC6H2-2,4,6-Cy3)(O2C6H-3,5,6-Cy3)]2, was obtained via ligand rearrangement of3at ca. 180 °C. This yielded4in which there are
two unchanged, bridging phenoxide ligands as well as a terminal bidentate
semiquinone ligand bound to each cobalt. Complexes1and2did not undergo such a rearrangement under the same conditions;
both are thermally stable to temperatures exceeding 250 °C and
feature numerous short-contact (<2.5 Å) H···H
interactions consistent with the presence of dispersion stabilization.
Use of the aryloxide ligand −OC6H3-2,6-Pri2(Pri= isopropyl), which is sterically similar to −OC6H2-2,4,6-Cy3but produces fewer close H···H
interactions, gave the trimeric species [M(OC6H3-2,6-Pri2)2]3{M = Fe (5) or Co (6)} which feature
a linear array of three metal atoms bridged by aryloxides. The higher
association number in5and6in comparison
to that of1–3is due to the lower dispersion
energy donor properties of the −OC6H3-2,6-Pri2ligand and the lower
stabilization it produces.