A solid-state NMR investigation of the structure of mesoporous silica nanoparticle supported rhodium catalysts

Rapp, Jennifer L.; Huang, Yangen; Natella, Michael; Cai, Yang; Lin, Victor S.‐Y.; Pruski, Marek

doi:10.1016/j.ssnmr.2008.12.004

Cited by 28 publications

(15 citation statements)

References 60 publications

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“…Evidence of immobilization of the Rh I phosphine complex on AlSBA-15i sr eflected by the two main 31 PC PMAS NMR signals observed around 44 ppm and 34 ppm, whichw ere assigned to surface-bound oxidizedp hosphine and phosphine-rhodium(I) complexes, respectively.T he latter peak positionc onforms well with previously reported 31 Pc hemical shifts (35-37ppm) observed from different silica-surfacei mmobilized Rh I phosphine complexes. [40,41] The presence of silica bound phosphine oxide observed in the 31 PC PMASN MR spectra indicates that complex 3 undergoes structuralc hanges when binding to the mesoporous surfacea nd that the supported catalyst may contain only one phosphine ligand boundt or hodium, the other having been oxidized during the immobilization process or upon storage (the samples were kept in air). Nevertheless,t wo equivalents of phosphine 1b were needed to prepare II/AlSBA-15.…”

Section: Pn Mrmentioning

confidence: 99%

Single Site Supported Cationic Rhodium(I) Complexes for the Selective Redox Isomerization of Allylic Alcohols

et al. 2012

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The isomerization of allylic alcohols to carbonyl compounds by a heterogeneous rhodium complex is reported. Different silica material supports and catalyst/ligand systems were evaluated. The most efficient catalyst in terms of catalytic activity and stability was found to be a cationic rhodium(I) complex with sulfonated phosphine ligands anchored on a mesoporous aluminosilica AlSBA‐15. The heterogeneous complex catalyzed the isomerization of a variety of allylic alcohols in excellent yields with very low catalyst loadings (0.5 mol %). The catalyst could be recycled without significant loss of activity or selectivity. The optimized catalyst was characterized by N2 sorption, powder X‐ray diffraction, transmission electron microscopy, as well as solution and solid‐state nuclear magnetic resonance, and Fourier Transform infrared spectroscopies.

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Section: Pn Mrmentioning

confidence: 99%

Single Site Supported Cationic Rhodium(I) Complexes for the Selective Redox Isomerization of Allylic Alcohols

et al. 2012

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“…Cross-polarization (CP) and direct polarization (DP) excitation methods in concert with magic spinning (MAS) allows one to obtain qualitative and quantitative information on composition, surface and bulk properties, local molecular environment of diverse silicon containing materials such as silica gels [12, 15], organosilicon polymers and resins [9, 16], mesoporous materials [17, 18], hybrid inorganic–organic materials [4, 5]. …”

Section: Introductionmentioning

confidence: 99%

A Solid-State NMR Investigation of MQ Silicone Copolymers

et al. 2013

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The structure of MQ copolymers of the general chemical formula [(CH3)3SiO0.5]m [SiO2]n was characterized by means of solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The MQ copolymers are highly branched polycyclic compounds (densely cross-linked nanosized networks). MQ copolymers were prepared by hydrolytic polycondensation in active medium. 29Si NMR spectra were obtained by single pulse excitation (or direct polarization, DP) and cross-polarization (CP) 29Si{1H} techniques in concert with MAS. It was shown that material consist of monofunctional M (≡SiO Si (CH3)3) and two types of tetrafunctional Q units: Q4 ((≡SiO)4Si) and Q3 ((≡SiO)3SiOH). Spin–lattice relaxation times T1 measurements of 29Si nuclei and analysis of 29Si{1H} variable contact time signal intensities allowed us to obtain quantitative data on the relative content of different sites in copolymers. These investigations indicate that MQ copolymers represent dense structure with core and shell.

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“…Owing to these favorable properties several studies of immobilized species on surfaces employing modern techniques of solidstate NMR are reported in the literature. [23,[52][53][54] In this work we use a combination of 29 Si and advanced 31 P solid-state NMR methods to investigate and characterize modified surface of mesoporous silica and to study the exact binding of Wilkinsons complex to the modified silica surface. We demonstrate that the 31 P J-resolved 2D slow-spinning magic-angle-spinning (MAS) and Off-MAS 31 P NMR techniques are efficient tools to reveal the detailed binding situation of the supported [RhClA C H T U N G T R E N N U N G (PPh 3 ) 3 ] molecule.…”

Section: Introductionmentioning

confidence: 99%

Solid‐State NMR Characterization of Wilkinson’s Catalyst Immobilized in Mesoporous SBA‐3 Silica

Grünberg

Breitzke

et al. 2010

Chemistry A European J

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The Wilkinson's catalyst [RhCl(PPh(3))(3)] has been immobilized inside the pores of amine functionalized mesoporous silica material SBA-3 and The structure of the modified silica surface and the immobilized rhodium complex was determined by a combination of different solid-state NMR methods. The successful modification of the silica surface was confirmed by (29)Si CP-MAS NMR experiments. The presence of the T(n) peaks confirms the successful functionalization of the support and shows the way of binding the organic groups to the surface of the mesopores. (31)P-(31)P J-resolved 2D MAS NMR experiments were conducted in order to characterize the binding of the immobilized catalyst to the amine groups of the linkers attached to the silica surface. The pure catalyst exhibits a considerable (31)P-(31)P J-coupling, well resolvable in 2D MAS NMR experiments. This J-coupling was utilized to determine the binding mode of the catalyst to the linkers on the silica surface and the number of triphenylphosphine ligands that are replaced by coordination bonds to the amine groups. From the absence of any resolvable (31)P-(31)P J-coupling in off-magic-angle-spinning experiments, as well as slow-spinning MAS experiments, it is concluded, that two triphenylphosphine ligands are replaced and that the catalyst is bonded to the silica surface through two linker molecules.

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A solid-state NMR investigation of the structure of mesoporous silica nanoparticle supported rhodium catalysts

Cited by 28 publications

References 60 publications

Single Site Supported Cationic Rhodium(I) Complexes for the Selective Redox Isomerization of Allylic Alcohols

Single Site Supported Cationic Rhodium(I) Complexes for the Selective Redox Isomerization of Allylic Alcohols

A Solid-State NMR Investigation of MQ Silicone Copolymers

Solid‐State NMR Characterization of Wilkinson’s Catalyst Immobilized in Mesoporous SBA‐3 Silica

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