Synthesis, Properties, and Reactivity of Diketiminate-Supported Cobalt Fluoride Complexes

Reaction of the three-coordinate cobalt(II) methyl complex LtBuCoCH3 (LtBu = bulky β-diketiminate ligand) with (CH3)3SnF gives an interesting trimetallic complex, [LtBuCo(μ-F)2]2Sn(CH3)2 (1). Magnetic susceptibility studies indicate that 1 consists of two mixed-valence cobalt(II/III) fluoride units bridged by the organometallic tin(III) fragment [SnF2(CH3)2]−. The addition of pyridine releases the tin bridge, and the cobalt fluoride species can be isolated as the high-spin cobalt(II) complex LtBuCoF(py) (2). Treating 2 with triethylsilane in an effort to form LtBuCoH(py) gave instead the high-spin cobalt(I) complex LtBuCo(py), with elimination of H2. Attempts at catalytic or stoichiometric hydrodefluorination of fluorinated aromatics with silane using 2 as a catalyst were unsuccessful. The lack of hydrodefluorination activity may be due to H2 elimination from low-coordinate cobalt hydride complexes or from inhibition by a fourth donor to the metal.