Dissolution of [RhCl(PPh3)3] in the ionic liquid, 1-ethyl-3-methyl imidazolium chloroaluminate(III), and its reaction with H2. The stabilization of Rh(I) species in an ionic liquid

The solution of [RhCl(PPh3)3] in acidic 1-ethyl-3-methylimidazolium chloroaluminate(III) ionic liquid (AlCl3 molar fraction, xAlCl3=0.67) was investigated by 1H and 31P{1H} NMR. One triphenyl phosphine is lost from the complex and is protonated in the acidic media, and cis-[Rh(PPh3)2ClX], (2), where X is probably [AlCl4]−, is formed. On, standing, 2 is converted to trans-[Rh(H)(PPh3)2X], (3). The reaction of 2 and H2 also produces trans-[Rh(H)(PPh3)2X], (3). 1H and 31P{1H} NMR support the suggestion that a weak ligand such as [AlCl4]−, present in solution may interact with the metal centre. When [RhCl(PPh3)3] is dissolved in CH2Cl2/AlCl3/HCl for comparison, two exchanging isomers of what is probably [RhH{(μ-Cl)2AlCl2}{(μ-Cl)AlCl3}(PPh3)2], (6) and (7), are formed.