Hemilability of phosphine-thioether ligands coordinated to trinuclear Mo 3 S 4 clusters and its effect on hydrogenation catalysis Artem L. Gushchin, a,b * Nikita Y. Shmelev, a,b Svetlana F. Malysheva, c Alexander V. Artem’ev, a Nataliya A. Belogorlova, c Pavel A. Abramov, a Nikolay B. Kompan’kov, a Eric Manoury, d Rinaldo Poli, d Dmitriy G. Sheven, a Rosa Llusar, e Maxim N. Sokolov, a,b a Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, 3 Lavrentiev av., Novosibirsk, 630090, Russia b Novosibirsk State University, 2 Pirogov str., Novosibirsk, 630090, Russia c Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, 1 Favorsky str., Irkutsk, 664033, Russia d Universite de Toulouse, UPS, INPT, 205, route de Narbonne, Toulouse F-31077, France e Departament de Química Física i Analítica, Universitat Jaume I, Av. Sos Baynat s/n, 12071 Castelló, Spain ABSTRACT Ligand-exchange reactions of [Mo 3 S 4 (tu) 8 (H 2 O)]Cl 4 4H 2 O (tu = thiourea) with (PhCH 2 CH 2 ) 2 PCH 2 CH 2 SR ligands, where R = Ph (PS1), pentyl (PS2) or Pr (PS3) afford new complexes isolated as [Mo 3 S 4 Cl 3 (PS1) 3 ]PF 6 ([1]PF 6 ), [Mo 3 S 4 Cl 3 (PS2) 3 ]PF 6 ([2]PF 6 ) and [Mo 3 S 4 Cl 3 (PS3) 3 ]PF 6 ([3]PF 6 ) salts in 30-50% yields as the major reaction products. The crystal structures of [1]PF 6 and [2]PF 6 were determined by X-ray diffraction (XRD) analysis. Each of the three phosphine-thioether ligands is coordinated in a bidentate chelating mode to a different molybdenum atom of the Mo 3 S 4 trinuclear cluster, herewith all the phosphorus atoms of the phosphino-thioether ligand are located trans to the capping sulfur ( 3 -S). A second product that forms in the reaction of [Mo 3 S 4 (tu) 8 (H 2 O)]Cl 4 4H 2 O with PS1 corresponds to the neutral [Mo 3 S 4 Cl 4 (PS1) 2 (PS1*)] complex. Its XRD analysis reveals both bidentate (PS1) and monodentate (PS1*) coordinating modes of the same ligand. In the latter mode the phosphine- thioether is coordinated to a Mo atom only via the P atom. All compounds were characterized by 1 H, 31 P{ 1 H} NMR, electrospray-ionization (ESI) mass spectrometry and cyclic voltammetry (CV). Reactions of [1]PF 6 , [2]PF 6 and [3]PF 6 with an excess of Bu 4 NCl in CD 2 Cl 2 were followed by 31 P{ 1 H} NMR. The spectra indicate equilibrium between cationic [Mo 3 S 4 Cl 3 (PSn) 3 ] + and neutral [Mo 3 S 4 Cl 4 (PSn) 2 (PSn*)] (n = 1, 2) species. The equilibrium constants were determined