Four‐Coordinate Trispyrazolylboratomanganese and ‐iron Complexes with a Pyrazolato Co‐ligand: Syntheses and Properties as Oxidation Catalysts

摘要: A series of complexes the type [(Tp(R1,R2))M(X)] (Tp = trispyrazolylborato) with R(1)/R(2) combinations Me/tBu, Ph/Me, iPr/iPr, Me/Me and for M Mn or Fe coordinating [Pz(Me,tBu)](-) (Pz pyrazolato) Cl(-) as co-ligand X has been synthesised. Although chloride were very unreactive stable in air, pyrazolato was far more reactive contact oxidants like O(2) tBuOOH. The [(Tp(R1,R2))M(Pz(Me,tBu))] proved to be active pre-catalysts oxidation cyclohexene tBuOOH, reaching turnover frequencies (TOFs) ranging between moderate good comparison other manganese catalysts. Cyclohexene-3-one cyclohexene-3-ol always found represent main products, oxide occasionally formed a side product. ratios different products varied reaction conditions: case peroxide/alkene ratio 4:1, considerably ketone than alcohol obtained formation almost negligible, whereas 1:10 led significant increase proportion at least small amounts epoxide. Pre-treatment dissolved product distributions TOFs that similar those absence O(2), so it may argued tBuOOH both lead same species. results EPR spectroscopy ESI-MS suggest initial [(Tp(Me,Me))Mn(Pz(Me,tBu))] contains Mn(III)(O)(2)Mn(IV) core. Prolonged exposure leads dinuclear complex containing three O-bridges resulting TOFs/product distributions. Analogous findings made these overoxidised explain deviation catalytic performances if reactions are carried out an atmosphere.