Infrared Spectra and Structures of Some Metal Hexacarbonyl Derivatives

Stolz, Ingo W.; Dobson, Gerard R.; Sheline, Raymond K.

doi:10.1021/ic50006a020

Cited by 56 publications

(18 citation statements)

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“…2 h required by CyCONH 2 , induction periods of 6 and greater than 8 h, respectively, were evident with the secondary amides CyCONHCH 3 and HCONHCH 3 ; throughout which the presence of [H 3 Ru 4 (CO) 12 ] À was retained. There is ample precedence for the formation of amide-substituted metal carbonyls, particularly with Mo, [21] although the situation with respect to Ru is less clear. Both the stoichiometry and stability of such products are likely to be dictated by the nature of the individual amide, which can therefore reasonably be expected to lead to variations in the degree of inhibition towards complete decomposition.…”

Section: Has Been Consumed [H 3 Ru 4 (Co) 12 ]mentioning

confidence: 99%

“…Both the stoichiometry and stability of such products are likely to be dictated by the nature of the individual amide, which can therefore reasonably be expected to lead to variations in the degree of inhibition towards complete decomposition. Hence the most likely explanation for the variation in length of the induction periods is an amide-dependent stabilisation of Mo(CO) 6Àx A C H T U N G T R E N N U N G (amide) x (x = 1-3), [21] which in turn limits the rate of total decomposition at 160 8C and allows the controlled assembly of the respective Ru/Mo catalysts. …”

Section: Has Been Consumed [H 3 Ru 4 (Co) 12 ]mentioning

confidence: 99%

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Selective Hydrogenation of Amides using Ruthenium/ Molybdenum Catalysts

et al. 2010

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Recyclable, heterogeneous bimetallic ruthenium/molybdenum catalysts, formed in situ from triruthenium dodecacarbonyl [Ru 3 (CO) 12 ] and molybdenum hexacarbonyl [Mo(CO) 6 ], are effective for the selective liquid phase hydrogenation of cyclohexylcarboxamide (CyCONH 2 ) to cyclohexanemethylamine (CyCH 2 NH 2 ), with no secondary or tertiary amine by-product formation. Variation of Mo:Ru composition reveals both synergistic and poisoning effects, with the optimum combination of conversion and selectivity at ca. 0.5, and total inhibition of catalysis evident at ! 1. Good amide conversions are noted within the reaction condition regimes 20-100 bar hydrogen and 145-160 8C. The order of reactivity of these catalysts towards reduction of different amide functional groups is primary > tertiary @ secondary. In situ HP-FT-IR spectroscopy confirms that catalyst genesis occurs during an induction period associated with decomposition of the organometallic precursors. Ex situ characterisation, using XRD, XPS and EDX-STEM, for active Mo:Ru compositions, has provided evidence for intimately mixed ca. 2.5-4 nm particles that contain metallic ruthenium, and molybdenum (in several oxidation states, including zero).

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Section: Has Been Consumed [H 3 Ru 4 (Co) 12 ]mentioning

confidence: 99%

Section: Has Been Consumed [H 3 Ru 4 (Co) 12 ]mentioning

confidence: 99%

Selective Hydrogenation of Amides using Ruthenium/ Molybdenum Catalysts

et al. 2010

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“…There is significant precedent for the photochemical formation of DMF metal carbonyl complexes, [8] in which the electron-deficient ketone carbon atom is activated towards hydrosilylation chemistry. There is significant precedent for the photochemical formation of DMF metal carbonyl complexes, [8] in which the electron-deficient ketone carbon atom is activated towards hydrosilylation chemistry.…”

Section: Hemant K Sharma and Keith H Pannell*mentioning

confidence: 99%

The Photochemical Irradiation of R₃SiH in the Presence of [(η⁵‐C₅H₅)Fe(CO)₂CH₃] in DMF Leads to Disiloxanes not Disilanes

Sharma

Pannell

2009

Angewandte Chemie

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“…Unlike the situation on silica, there is clear evidence of stepwise decarbonylation [22]. The adsorbed carbonyl reacts at -10°C [27], and the species formed exhibits a similar infrared spectrum in the M-C-O region [22] to those of Mo(CO)5 centres solvated by alcohols or ethers [28]; there has effectively been a monosubstitution reaction of a CO ligand by a surface Lewis base site ( .. "Mo(CO)4 ads" Thermolysis at 100°C causes the loss of a further 2 CO groups, and the re-coordination of one and two CO ligands occurs at different temperatures [29,30]. So there appear to be two more materials of apparent composition MoO(CO)n ads (n = 4 and 5).…”

Section: Mo(co)6 Ads + 5(ho-[si]) 25h2 + 6co + Mv(o-[si])5mentioning

confidence: 99%

Reaction of Organometallics with Surfaces of Metal Oxides

Evans

1988

Surface Organometallic Chemistry: Molecular Approaches to Surface Catalysis

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Organometallic complexes can be introduced onto metal oxide supports either by direct bonding or via an intervening ligand. The former method uses the diverse reaction sites available on oxide surfaces. The chemisorption processes may be considered in the same way as reactions of organometallic complexes in solution. For example, interaction of Rh(allyl)3 with silica causes an electrophilic cleavage of one metal-allyl bond to generate a new metal centre, viz.[Si]-ORh(allyl)2' Alternatively, interaction of RU3(CO)12 with silica proceeds via an oxidative addition reaction of a silanol group across one of the metal-metal bonds. Nuclearity is not always maintained during anchoring procedures, as in the case of the interaction of Rh4(CO)12 with alumina, in which mononuclear metal centres are produced. Some of the coordination centres derived from these grafted organometallic complexes have close analogues in mainstream organometallic chemistry; others appear to have no discrete counterpart at present and offer a challenge to the synthetic chemist. Organometallics also provide alternative routes to supported metal particles. In some instances these may be formed under much milder conditions than conventional reductions of metal salts. By virtue of the differing kinetics involved, different (often smaller) particle sizes, compositions, and size distributions become available. Ligandtethered complexes may be synthesised with high specificity. However, subsequent surface reactions occur to give new coordination centres. If the aim is to anchor a known homogeneous catalyst, then precautions must be taken to avoid these, either by protective silylation or by design of a stabilising tethering ligand. But the original tethered complex may be used as a catalyst precursor, and so these surface reactions may be of interest. Many new catalysts have been prepared by supporting organometallic complexes on oxide supports. Establishing the metal coordination site requires a combination of total product analysis and direct spectroscopic measurements characterizing the supported complex, preferably aided by reference to close model compounds. This is now considerably easier with the range of techniques presently available. For a high proportion of materials, the oxide surface binding site is not understood. Progress in this is necessary 47

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Infrared Spectra and Structures of Some Metal Hexacarbonyl Derivatives

Cited by 56 publications

References 0 publications

Selective Hydrogenation of Amides using Ruthenium/ Molybdenum Catalysts

Selective Hydrogenation of Amides using Ruthenium/ Molybdenum Catalysts

The Photochemical Irradiation of R₃SiH in the Presence of [(η⁵‐C₅H₅)Fe(CO)₂CH₃] in DMF Leads to Disiloxanes not Disilanes

Reaction of Organometallics with Surfaces of Metal Oxides

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Infrared Spectra and Structures of Some Metal Hexacarbonyl Derivatives

Cited by 56 publications

References 0 publications

Selective Hydrogenation of Amides using Ruthenium/ Molybdenum Catalysts

Selective Hydrogenation of Amides using Ruthenium/ Molybdenum Catalysts

The Photochemical Irradiation of R3SiH in the Presence of [(η5‐C5H5)Fe(CO)2CH3] in DMF Leads to Disiloxanes not Disilanes

Reaction of Organometallics with Surfaces of Metal Oxides

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The Photochemical Irradiation of R₃SiH in the Presence of [(η⁵‐C₅H₅)Fe(CO)₂CH₃] in DMF Leads to Disiloxanes not Disilanes