Synthesis and catalytic applications of Ru(II)-phosphaurotropine complexes with the use of simple water-soluble Ru(II)-precursors

Abstract 1,3,5-Triaza-7-phosphaadamantane (pta, phosphaurotropine) played a special role in the development of aqueous organometallic chemistry and catalysis. The main reason is in its easy synthesis, oxidation stability, versatile possibilities of functionalization, and high solubility not only in water but also in several common organic solvents. Such favourable solubility behaviour allowed straightforward synthesis of pta-containing transition metal complexes from simple, inexpensive, often commercial starting materials. A further advantage of pta and its complexes is in their pronounced tendency to crystallize which allowed determination of solid-state structures of a great number of such compounds. This review covers synthetic procedures of ruthenium(II)-complexes with pta, and N-alkyl-pta derivatives as ligands, as well as their most important reactions in aqueous systems. Ru(II)-pta complexes were employed as catalysts in several important aqueous-phase processes such as selective hydrogenation and transfer hydrogenation of aldehydes, hydration of nitriles, and redox isomerization of allylic alcohols. Hydrogenation of carbon dioxide/bicarbonate and dehydrogenation of formic acid/aqueous formate were also studied with various Ru(II)-complexes of phosphaurotropines. Altogether the results described in this review made a significant positive impact on the development of green chemical processes.