Parahydrogen-induced polarization with a Rh-based monodentate ligand in water

Abstract

Reported here is a water-soluble Rh(I)-based catalyst for performing parahydrogen-induced polarization (PHIP). The [Rh(I)(norbornadiene)(THP) 2]+[BF4]- catalyst utilizes the monodentate phosphine ligand tris(hydroxymethyl)phosphine (THP). The monodentate PHIP catalyst is less susceptible to oxygenation by air and the THP ligand is significantly less expensive than bidentate water-soluble PHIP ligands. In situ PHIP detection with this monodentate Rh(I)-based catalyst in water yielded 12% 13C polarization for the parahydrogen addition product, 2-hydroxyethyl 1-13C-propionate-d2,3,3 (HEP), with a 13C T1 relaxation of 108 s at 0.0475 T. PHIP polarization yields were high, reflecting efficient hydrogenation even under conditions of high content of the oxidized phosphine form of the THP ligand. © 2012 American Chemical Society.