Treatment of cobaloximes(II),
[Co(Hdmg)2(L)2] (Hdmg = dimethylglyoximate,
L = neutral ligand), with perfluoroalkyl
iodane reagents leads to the formation of perfluoroalkyl cobaloximes(III),
[CoRF(Hdmg)2(L)] (RF = CF3, C2F5, n-C3F7, CF2CF2Ph; L = Py, NH3, MeNH2, PhNH2, MeOH). The synthetic protocol can be significantly simplified
to a one-pot procedure starting from cobalt(II) acetate–tetrahydrate.
The products have been fully characterized by NMR, IR, and UV/vis
spectroscopy as well as single-crystal X-ray diffraction, and the
thermal and photochemical reactivity has been studied. According to
the Co–L distances in the crystal, the trans influence of the RF
– ligands can be
rated as C2F5
– ≈ n-C3F7
– < CF2CF2Ph– ≈ CF3
– < CH3
–. The thermal
decomposition of the complexes is different from that of nonfluorinated
analogues, probably including perfluoroalkylation of an Hdmg– ligand as the initial step. In the CF3 complexes, the
Co–C bond is very resistant against photolysis, but the ligand
L is readily exchanged by MeOH upon exposure to blue light. In the
complexes with longer RF chains, the Co–C bond is
more readily cleaved, and the product distribution depends strongly
on the presence of O2. Thus, the alkane RFH
is the main product under exclusion of O2, while a fluorinated
methyl ester and HF are formed in a methanol solution exposed to air.