| Abstract: | The dioxovanadium(V) complexes VO2(3,5‐Me2Hpz)3]BF4] ( 1 ) (pz=pyrazolyl), VO2{SO3C(pz)3}] ( 2 ), VO2{HB(3,5‐Me2pz)3}] ( 3 ) and VO2{HC(pz)3}]BF4] ( 4 ), bearing pyrazole or scorpionate ligands, were obtained by reaction of triethyl vanadate VO(OEt)3] with hydrotris(3,5‐dimethyl‐1‐pyrazolyl)methane HC(3,5‐Me2pz)3] or 3,5‐dimethylpyrazole (3,5‐Me2Hpz; 1 ), lithium tris(1‐pyrazolyl)methanesulfonate {LiSO3C(pz)3], 2 }, potassium hydrotris(3,5‐dimethyl‐1‐pyrazolyl)borate {KHB(3,5‐Me2pz)3], 3 } and hydrotris(1‐pyrazolyl)methane HC(pz)3, 4 ], respectively. Treatment of VO(OEt)3] with potassium hydrotris(1‐pyrazolyl)borate {KHB(pz)3]} led to the mixed η3‐tris(pyrazolyl)borate and η2‐bis(pyrazolyl)borate oxovanadium(IV) complex VO{HB(pz)3}{H2B(pz)2}, 5 ]. The compounds were characterized by elemental analyses, IR, NMR and EPR spectroscopy, FAB and ESI mass spectrometry, cyclic voltammetry and, for 5 , also by single crystal X‐ray diffraction analysis. All complexes exhibit catalytic activity in the single‐pot carboxylation in trifluoroacetic acid/potassium peroxodisulfate (CF3COOH/K2S2O8)] of gaseous alkanes (methane and ethane) to carboxylic acids (yields up to 40%, TONs up to 157) and in the peroxidative oxidation in water/acetonitrile (H2O/NCMe)] of liquid alkanes (cyclohexane and cyclopentane) to the corresponding alcohols and ketones (yields up to 24%, TONs up to 117), under mild conditions. |
