Hydride Mobility in Trinuclear Sulfido Clusters with the Core [Rh3(μ-H)(μ3-S)2]: Molecular Models for Hydrogen Migration on Metal Sulfide Hydrotreating Catalysts

• Published in: Chemistry : a European journal 2011-07, Vol.17 (29), p.8115-8128
• Main Authors: Jiménez, M. Victoria, Lahoz, Fernando J., Lukešová, Lenka, Miranda, José R., Modrego, Francisco J., Nguyen, Duc H., Oro, Luis A., Pérez-Torrente, Jesús J.
• Format: Article
• Language: English
• Subjects: Alkadienes - chemistry; Catalysis; Chemistry; cluster compounds; Crystallography, X-Ray; hydrides; Hydrogen - chemistry; Models, Molecular; Norbornanes - chemistry; rhodium; Rhodium - chemistry; Sulfides - chemistry; sulfur
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201100138

The treatment of [{Rh(μ‐SH){P(OPh)3}2}2] with [{M(μ‐Cl)(diolef)}2] (diolef=diolefin) in the presence of NEt3 affords the hydrido–sulfido clusters [Rh3(μ‐H)(μ3‐S)2(diolef){P(OPh)3}4] (diolef=1,5‐cyclooctadiene (cod) for 1, 2,5‐norbornadiene (nbd) for 2, and tetrafluorobenzo[5,6]bicyclo[2.2.2]octa‐2,5,7‐triene (tfb) for 3) and [Rh2Ir(μ‐H)(μ3‐S)2(cod){P(OPh)3}4] (4). Cluster 1 can be also obtained by treating [{Rh(μ‐SH){P(OPh)3}2}2] with [{Rh(μ‐OMe)(cod)}2], although the main product of the reaction with [{Ir(μ‐OMe)(cod)}2] was [RhIr2(μ‐H)(μ3‐S)2(cod)2{P(OPh)3}2] (5). The molecular structures of clusters 1 and 4 have been determined by X‐ray diffraction methods. The deprotonation of a hydrosulfido ligand in [{Rh(μ‐SH)(CO)(PPh3)}2] by [M(acac)(diolef)] (acac=acetylacetonate) results in the formation of hydrido–sulfido clusters [Rh3(μ‐H)(μ3‐S)2(CO)2(diolef)(PPh3)2] (diolef=cod for 6, nbd for 7) and [Rh2Ir(μ‐H)(μ3‐S)2(CO)2(cod)(PPh3)2] (8). Clusters 1–3 and 5 exist in solution as two interconverting isomers with the bridging hydride ligand at different edges. Cluster 8 exists as three isomers that arise from the disposition of the PPh3 ligands in the cluster (cis and trans) and the location of the hydride ligand. The dynamic behaviour of clusters with bulky triphenylphosphite ligands, which involves hydrogen migration from rhodium to sulfur with a switch from hydride to proton character, is significant to understand hydrogen diffusion on the surface of metal sulfide hydrotreating catalysts. Bridged with H and S: Trinuclear clusters with [M3(μ‐H)(μ3‐S)2] cores have been prepared from bis‐(hydrosulfido)‐bridged dinuclear rhodium(I) compounds (see figure). The migration of the hydride ligand between the edges of the metallic triangle through a mechanism assisted by the sulfido ligands has been observed in some cases.