Organic borate-based catalyst, method for preparing isobutene oligomer using the same and isobutene oligomer prepared thereby

An organic borate-based catalyst comprising a compound represented by Formula 1 and a hydroxyl group-containing compound, wherein

• a silicon atom (Si) of the compound represented by Formula 1 and an oxygen atom (O) of the hydroxyl group-containing compound form a covalent bond:
• in Formula 1,
• each R0 is independently hydrogen, an alkyl group of 1 to 20 carbon atoms, an alkoxy group of 1 to 20 carbon atoms, an aryl group of 6 to 20 carbon atoms or an aryloxy group of 6 to 20 carbon atoms,
• R1 to R4 are each independently hydrogen, a halogen group or an alkyl group of 1 to 20 carbon atoms, and
• o, p, q and r are each independently an integer of 1 to 5,
• wherein the hydroxyl group-containing compound is a compound represented by Formula 2:
• in Formula 2,
• R5 to R7 are each independently hydrogen, a hydroxyl group, a hydroxyalkyl group of 1 to 20 carbon atoms, an alkyl group of 1 to 20 carbon atoms, an alkenyl group of 2 to 20 carbon atoms, an alkynyl group of 2 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, an aryl group of 6 to 20 carbon atoms, a heteroaryl group of 5 to 20 carbon atoms, an alkoxy group of 1 to 20 carbon atoms, an aryloxy group of 6 to 20 carbon atoms, an alkylaryl group of 7 to 20 carbon atoms or an arylalkyl group of 7 to 20 carbon atoms, provided that at least two of R5 to R7 are not hydrogen, and one of R5 to R7 is an aryl group of 6 to 20 carbon atoms, a heteroaryl group of 5 to 20 carbon atoms, or an aryloxy group of 6 to 20 carbon atoms.