Characterization of silica-supported osmium carbonyl clusters by magic-angle-spinning carbon-13 NMR spectroscopy

Observing the three-dimensional dynamics of supported metal complexes

“…SSNMR measurements are site-specific, meaning that the motions throughout a molecule, or ligand, can be determined independently and their relationships can be used to elucidate the three-dimensional conformation space of a catalyst. This potential has already been demonstrated with the SSNMR observation of dynamic ligand exchange [38][39][40][41] as well as the observation that the metal dynamics in silica-supported Mo, Ta, W, and Re alkylidene catalysts may be related to the identity of the metal, with the lighter Mo catalysts being bound more tightly to the surface. 42 There is also SSNMR evidence that the "roughness" of the silica surface may prevent certain motional modes in surface-supported moieties.…”

Surface-Mediated Organometallic Synthesis: The Activating Role of Silica for a High-Yield Route to [H4Os4(CO)12] and [HOs3(CO)10Y] (Y = OH, OR, Cl, Br, I, O2CR, SCN) Clusters from [Os3(CO)12]

“…As in other cases, ,− high yields and selectivities together with rather mild reaction conditions characterize these new synthetic routes mediated by the silica surface. In this specific work, we have the limitation, from the synthetic point of view, that the formation of silica-anchored [HOs 3 (CO) 10 (OSi⋮)] species is controlled by the number of specific available silanol groups on the silica surface, so that only loadings of the surface up to 4 wt % Os/SiO 2 have been achieved . However, the simplicity of the two-step (in one pot ) or three-step (via [HOs 3 (CO) 10 (OH)] ) methodology and the very high total yields and selectivities from [Os 3 (CO) 12 ] make the methodology still rather attractive.…”

“…In this specific work, we have the limitation, from the synthetic point of view, that the formation of silicaanchored [HOs 3 (CO) 10 (OSit)] species is controlled by the number of specific available silanol groups on the silica surface, 31 so that only loadings of the surface up to 4 wt % Os/SiO 2 have been achieved. 32 However, the simplicity of the two-step (in one pot) or three-step (via [HOs 3 (CO) 10 (OH)]) methodology and the very high total yields and selectivities from [Os 3 (CO) 12 ] make the methodology still rather attractive. In any case, amounts of 200-300 mg of final product can be easily obtained using ∼10 g of silica, which can be recycled after workup and completion of the reaction.…”

Synthesis and Characterization of Osmium-Containing Silsesquioxanes: High-Yield Routes to {Os3(CO)10(μ-H)[(μ-O)Si7O10(c-C6H11)7]} and the New Clusters {Os3(CO)10(μ-H)[(μ-O)Si7O9(OH)2(c-C6H11)7]}, {[Os3(CO)10(μ-H)]2(μ-O)2Si7O9(OH)(c-C6H11Lucenti1, Feher2 2006Organometallics14180View full textAdd to dashboardCite

“…One of the early success stories in surface organometallic chemistry was the reaction of silica with [Os 3 (CO) 12 ], which produces a structurally well-defined silica-supported cluster attached to the surface via a single siloxy group. − A variety of techniques were used to characterize this cluster, and its structure was assigned unambiguously as [Os 3 (CO) 10 (μ-H)(μ-OSi⋮)] on the basis of IR, ,, Raman, , and solid-state NMR spectroscopies, EXAFS, , and computer modeling ,, or on the basis of its similarity to structurally analogous homogeneous compounds (e.g., [Os 3 (CO) 10 (μ-H)(μ-OSiR 3 )] (R = Et, Ph). ,,,,, This work convincingly established that (1) silica could indeed be viewed as a ligand, (2) the reaction of silica with an organometallic compound could be highly selective, and (3) the characterization of silica-supported complexes could be achieved with a degree of accuracy and confidence that is approaching the corresponding solution organometallic complexes.…”