Facile synthesis of [Ru(η2-O2CO)(pta)(η6-p-cymene)], an outstandingly active Ru(II) half-sandwich complex for redox isomerization of allylic alcohols

The water-soluble [RuCl2(pta)(eta(6)-p-cymene)] (pta = 1,3,5-triaza-7-phosphaadamantane) was applied as catalyst in the transposition of allylic alcohols, such as oct-l-en-3-ol in aqueous media. The isomerisation of oct-1-en-3-ol to octan-3-one took place only at pH > 10 buffer solutions or in the presence of alkali metal carbonates. The aqueous solution of "in situ" catalyst aRuCl(2)(pta)(eta(6)-p-cymene)] + 2 eq Na2CO3) could be reused in the biphasic isomerization of oct-1-en-3-ol for at least five times without a significant loss of the catalytic activity. It was demonstrated that carbonate is not only a base in this reaction but leads to formation of a highly active catalyst, [Ru(eta(2)-O2CO)(pta)(eta(6)-p-cymene)]. This compound was isolated as crystalline solid and characterized in detail (including X-ray diffraction). (C) 2016 Elsevier B.V. All rights reserved.