Synthesis and structures of Co bis-trifluoromethylpyrazolate complexes.

Reactions of Co(PMe3)3Cl or CoCl2 with 3,5-(CF3)2-PzNa in hexane give Co(PMe3)3(3,5-(CF3)2-Pz) (1) and Co(PMe3)3(3,5-(CF3)2-Pz)2 (2) respectively (3,5-(CF3)2-PzNa = sodium bis-trifluoromethylpyrazolate). Reaction of (3,5-(CF3)2-PzH) with Co(PMe3)4 produces the unusual complex [cis-Co(PMe3)4H2][Co(PMe3)(3,5-(CF3)2-Pz)3] (3) which formally contains a [Co(III)](+)[Co(II)](-) complex ion pair. Reaction of 3,5-(CF3)2-PzLi with an oxygenated suspension of CoCl2 and 3 equivalents of PMe3 gives (3,5-(CF3)2-Pz)2Co(μ-3,5-(CF3)2-Pz)(μ-OPMe3)Li(OPMe3)2 (4), while 2 reacts with LiOH to give [(PMe3)Co(μ-3,5-(CF3)2-Pz)2(μ(3)-OH)Li]2 (5). Both 2 and 3 react with O2 in toluene solution to give Co(OPMe3)2(3,5-(CF3)2-Pz)2 (6). All compounds have been characterized spectroscopically and by single crystal X-ray diffraction studies.