Synthesis and characterization of redox-active tris(pyrazolyl)borate cobalt complexes.

摘要: The reaction of CoX2 (X = Cl, Br, NO3) with KTpPh2 in tetrahydrofuran (THF) yields the half-sandwich compounds [TpPh2CoX] Cl 1, Br 2, NO33). [TpPh2CoBr] NaX N3, NO2) or potassium thiocyanate (KNCS) permits isolation N34, NCS 5, NO26). In contrast, cobalt(II) acetate [TpPh2Co(OAc)(HpzPh2)] 7 as a result B–N bond cleavage. Subsequent range β-diketones presence NaOMe produces β-diketonate complexes, [TpPh2Co(β-diketonate)] (β-diketonate acac 8, hfac 9, dbm 10, tmhd 11). IR spectroscopy suggests that TpPh2 ligands are κ3-coordinated and adopt bidentate coordination mode. Electronic spectra consistent four- five-coordinate species solution. X-Ray crystallographic studies reveal an intermediate cobalt centre hydrogen bonding interaction between pyrazole carbonyl oxygen. molecular structures 9 10 show centres square pyramidal geometries κ2-coordinated ligands. Cyclic voltammetric 6 irreversible one-electron reduction to Co(I). However, 11 undergo oxidation. redox potential reversibility increases steric bulk substituent on ligand increases.