Water‐Soluble Group 8 and 9 Transition Metal Complexes Containing a Trihydrazinophosphaadamantane Ligand: Catalytic Applications in Isomerization of Allylic Alcohols and Cycloisomerization of ( Z )‐Enynols in Aqueous Medium

An optimized synthesis of the 2,4,10‐trimethyl‐1,2,4,5,7,10‐hexaaza‐3‐phosphatricyclo[3.3.1.1 3,7 ]decane ligand (THPA) is described. It readily reacts with the dimers [{RuCl(μ‐Cl)(η 6 ‐arene)} 2 ] and [{MCl(μ‐Cl)(cod)} 2 ] to yield the corresponding mononuclear complexes [RuCl 2 (THPA)(η 6 ‐arene)] [arene=C 6 H 6 ( 4a ), p ‐cymene ( 4b ), 1,3,5‐C 6 H 3 Me 3 ( 4c ), C 6 Me 6 ( 4d )] and [MCl(THPA)(cod)] [M=Rh ( 7a ), Ir ( 7b )], respectively. Treatment of 4a and b with MeOTf affords the cationic derivatives [RuCl 2 (THPA‐Me)(η 6 ‐arene)][OTf] {arene=C 6 H 6 ( 5a ), p ‐cymene ( 5b ); THPA‐Me=1,2,4,10‐tetramethyl‐2,4,5,7,10‐pentaaza‐1‐azonia‐3‐phosphatricyclo[3.3.1.1 3,7 ]decane}. The arene‐ruthenium( II ) complexes 4a–d and 5a and b are efficient catalysts for the redox isomerization of allylic alcohols into carbonyl compounds in both THF and aqueous media. The catalytic systems can be recycled by a simple extraction process and used in up to 4 consecutive runs. All the water‐soluble complexes prepared in this work are able to promote the cycloisomerization of ( Z )‐enynols to afford furans in water, the best performance being obtained with the iridium catalyst 7b . Furthermore, 7b has shown an excellent recyclability (10 runs). This study represents the first example of iridium‐catalyzed cycloisomerization of ( Z )‐enynols.