Bert Klein Gebbink

Catalysis, Inorganic Chemistry, Organometallic Chemistry



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    ABSTRACT: Mononuclear, coordinatively unsaturated rhenium(V) dioxo species of the type XReO2 (X = Me, substituted cyclopentadienyl) have long been postulated as intermediates in rhenium-catalyzed deoxydehydration, but their characterization was precluded because of aggregation into dimeric or oligomeric structures. Using the bulky 1,2,4-tri-tert-butylcyclopentadienyl (Cp(ttt)) ligand, the rhenium(V) dioxo species (Cp(ttt))ReO2 could now be observed, in equilibrium with the dimeric form [(Cp(ttt))Re(O)μ-O]2, and characterized by NMR, IR, and UV-vis spectroscopies, as well as electrospray ionization mass spectrometry. (Cp(ttt))ReO2 is shown to be the primary product of reduction of the rhenium(VII) complex (Cp(ttt))ReO3 with PPh3 and demonstrated to react with ethylene glycol significantly faster than its dimeric counterpart, supporting its role as an intermediate in rhenium-catalyzed deoxydehydration reactions.
    Inorganic Chemistry 10/2015; 54(22). DOI:10.1021/acs.inorgchem.5b02366 · 4.76 Impact Factor
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    ABSTRACT: A series of Grubbs-type catalysts that contain lipase-inhibiting phosphoester functionalities have been synthesized and reacted with the lipase cutinase, which leads to artificial metalloenzymes for olefin metathesis. The resulting hybrids comprise the organometallic fragment that is covalently bound to the active amino acid residue of the enzyme host in an orthogonal orientation. Differences in reactivity as well as accessibility of the active site by the functionalized inhibitor became evident through variation of the anchoring motif and substituents on the N-heterocyclic carbene ligand. Such observations led to the design of a hybrid that is active in the ring-closing metathesis and the cross-metathesis of N,N-diallyl-p-toluenesulfonamide and allylbenzene, respectively, the latter being the first example of its kind in the field of artificial metalloenzymes.
    Chemistry - A European Journal 09/2015; 21(44). DOI:10.1002/chem.201502381 · 5.73 Impact Factor
  • Annette B Vliegenthart · Frank A L Welling · Michael Roemelt · Robertus J M Klein Gebbink · Matthias Otte ·
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    ABSTRACT: The first shape-persistent macrocycle 1 offering a Brønsted pair functionalized interior is described. Via postcyclization transformation, this heterosequenced compound can be obtained from its corresponding ester 2. The macrocycles differ dramatically in their characteristics such as solubility and appearance. Theoretical investigations suggest that those contrasts might originate from conformational changes due to the formation of a strong O-H-N hydrogen bond in 1.
    Organic Letters 08/2015; 17(17). DOI:10.1021/acs.orglett.5b01931 · 6.36 Impact Factor
  • Bartholomeus W. H. Saes · Dide G. A. Verhoeven · Martin Lutz · Robertus J. M. Klein Gebbink · Marc-Etienne Moret ·
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    ABSTRACT: The coordination chemistry of the diphosphine-ketone ligand 2,2′-bis(diphenylphosphino)benzophenone (Phdpbp) with nickel is reported. The ketone moiety does not bind to Ni(II) in the complex (Phdpbp)NiCl2, whereas reduction to Ni(I) or Ni(0) induces η2(C,O) coordination of the ketone to form the pseudotetrahedral complexes (Phdpbp)NiCl and (Phdpbp)Ni(PPh3). DFT calculations indicate that the metal-ketone bond is dominated by π back-donation; hence, Phdpbp functions as a hemilabile acceptor ligand in this series of complexes.
    Organometallics 05/2015; 34(12):150521131812002. DOI:10.1021/acs.organomet.5b00264 · 4.13 Impact Factor
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    ABSTRACT: A method for the regioselective transformation of dienes to carbonyl compounds has been developed. Electron-rich olefins react selectively to yield valuable aldehydes and ketones. The method is based on the catalyst [Fe(OTf)2(mix-BPBP)] with an oxidant combination of H2O2 (1.0 equiv.) and NaIO4 (1.5 equiv.); it uses mild conditions and short reaction times, and it outperforms other olefin cleavage methodologies.
    European Journal of Inorganic Chemistry 04/2015; 46(48). DOI:10.1002/chin.201548075 · 2.97 Impact Factor
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    ABSTRACT: A method for the regioselective transformation of dienes to carbonyl compounds has been developed. Electron-rich olefins react selectively to yield valuable aldehydes and ketones. The method is based on the catalyst [Fe(OTf)2(mix-BPBP)] with an oxidant combination of H2O2 (1.0 equiv.) and NaIO4 (1.5 equiv.); it uses mild conditions and short reaction times, and it outperforms other olefin cleavage methodologies. The combination of an Fe-based catalyst, [Fe(OTf)2(mix-BPBP)], and the oxidants H2O2 and NaIO4 can discriminate between electronically different double bonds and oxidatively cleave the electron-rich bond in dienes to yield aldehydes and ketones in a regioselective manner. The reaction requires mild conditions (0-50 C) and short reaction times (70 min).
    Berichte der deutschen chemischen Gesellschaft 04/2015; 2015(21). DOI:10.1002/ejic.201500213 · 2.94 Impact Factor
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    ABSTRACT: A Rh(NHC) phosphonate complex reacts with the lipases cutinase and candida antarctica lipase B resulting in the first (soluble) artificial metalloenzymes formed by covalent active site-directed hybridization. When compared to unsupported complexes, these new robust hybrids show enhanced chemoselectivity in the (competitive) hydrogenation of olefins over ketones.
    Chemical Communications 03/2015; 51(31). DOI:10.1039/C4CC09700A · 6.83 Impact Factor
  • Suresh Raju · Marc‐Etienne Moret · Robertus J. M. Klein Gebbink ·
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    ABSTRACT: In view of the depletion of petroleum oils, new synthetic routes for the sustainable production of chemicals, fuels, and energy from renewable biomass sources are currently widely investigated. In particular, nonedible sugars and polyols are promising starting materials to produce olefins by dehydration, deoxygenation, or deoxydehydration (DODH) of these poly vicinal alcohols. In this perspective, we highlight the recent evolution of rhenium-catalyzed dehydration and DODH of biomass-derived alcohols and polyols to obtain olefins. Improving over the classical acid-catalyzed dehydration reaction, rhenium-mediated systems are very selective and more active to provide high yields of olefin products, but dehydration alone cannot be used to fully defunctionalize sugars. This issue is addressed by a growing research effort in the field of Re-catalyzed DODH, which allows complete dehydroxylation to form olefins in high yield. Recent developments in this field include the development of new molecular rhenium catalysts, the application of cheaper and more available reductants, and a growing mechanistic understanding owing to both experimental and computational studies. Finally, recent efforts to move beyond rhenium toward cheaper metals (Mo, V) are discussed.Keywords: biomass; olefins; diols; polyols; rhenium; deoxygenation; dehydration; deoxydehydration
    ChemInform 03/2015; 46(11). DOI:10.1002/chin.201511302
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    Yuxing Huang · Marc‐Etienne Moret · Robertus J. M. Klein Gebbink ·
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    ABSTRACT: Biaryls are a common motif in both natural and synthetic chemicals. Several methods have recently been reported for the preparation of these compounds using direct arylation catalyzed by iron, other base metals, or transition-metal-free systems. To date, these methods have all required inert and/or forcing conditions, which limited their application in routine organic synthesis. In this article we report a protocol for direct arylation using a convenient FeCl3/1,10-phenanthroline system as precatalyst. The reaction proceeds under mild conditions (100 °C), under air, and with non-distilled solvent.
    European Journal of Organic Chemistry 02/2015; 2014(18). DOI:10.1002/ejoc.201301620 · 3.07 Impact Factor
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    Rafael Lima Oliveira · Wuliyasu He · Bert Klein Gebbink · Krijn P. de Jong ·
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    ABSTRACT: Palladium nanoparticles of similar size of ~2 nm were synthesized on different silica-based materials all functionalized with thiol groups i.e., Aerosil-380, SBA-15, Plugged SBA-15 and m-MCF. The resulting materials were used to study the influence of confinement of Pd nanoparticles in functionalized silica support on the Heck and the Suzuki reaction. In the case of the Heck reaction, for all catalysts it was proven that leached Pd species were responsible for activity. However, the catalysts based on ordered mesoporous silica were still able to restrict Pd particle growth giving rise to an enhanced stability. For the Suzuki reaction, stronger alkaline conditions were required and catalysts based on plugged SBA-15 showed a higher stability than those based on SBA-15 and m-MCF which both collapsed after the first cycle. At almost identical Pd particle size, ordered mesoporous materials enhance stability and particle growth is slowed down but not fully suppressed.
    01/2015; 5(3). DOI:10.1039/C4CY01517G
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    ABSTRACT: Azole antifungal agents, which are widely used as antifungal antibiotics, inhibit cytochrome P450 sterol 14α demethylase (CYP51). In this research, a group of 1-methylimidazole derivatives were synthesized for evaluation as antibacterial and antifungal agents. Antimicrobial evaluation revealed that some of these compounds exhibited significant antimicrobial activities against tested pathogenic fungi and bacteria, wherein compounds 3 and 8 were most potent. To find the action mechanism, all of these compounds were subjected to docking studies using the AutoDock 4.2 program. The results show that all of the azoles (2 – 5, 7, and 8) interacted with 14α-DM, wherein azole – heme coordination, hydrogen binding, and -cation interactions were involved in the drug – receptor interaction. These studies offer some useful references in order to understand the action mechanism; moreover, performing the molecular design or modification of this series as a lead compound can assist in identifying new and potent antimicrobial agents.
    Pharmaceutical Chemistry Journal 11/2014; 27 Nov.(2014). DOI:10.1007/s11094-014-1140-5 · 0.45 Impact Factor
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    ABSTRACT: Reaction of [PdClMe(P^N)2 ] with SnCl2 followed by Cl-abstraction leads to apparent PdC bond activation, resulting in methylstannylene species trans-[PdCl{(P^N)2 SnClMe}][BF4 ] (P^N=diaryl phosphino-N-heterocycle). In contrast, reaction of Pt analogues with SnCl2 leads to PtCl bond activation, resulting in methylplatinum species trans-[PtMe{(P^N)2 SnCl2 }][BF4 ]. Over time, they isomerise to methylstannylene species, indicating that both kinetic and thermodynamic products can be isolated for Pt, whereas for Pd only methylstannylene complexes are isolated. Oxidative addition of RSnCl3 (R=Me, Bu, Ph) to M(0) precursors (M=Pd or Pt) in the presence of P^N ligands results in diphosphinostannylene pincer complexes trans-[MCl{(P^N)2 SnCl(R)}][SnCl4 R], which are structurally similar to the products from SnCl2 insertion. This showed that addition of RSnCl3 to M(0) results in formal SnCl bond oxidative addition. A probable pathway of activation of the tin reagents and formation of different products is proposed and the relevancy of the findings for Pd and Pt catalysed processes that use SnCl2 as a co-catalyst is discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry 11/2014; 21(4). DOI:10.1002/chem.201404071 · 5.73 Impact Factor
  • Peter Spannring · Pieter C. A. Bruijnincx · Bert. M. Weckhuysen · Robertus J. M. Klein Gebbink ·
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    ABSTRACT: The oxidative cleavage of the C=C double bond in unsaturated fatty acids into aldehydes or carboxylic acids is a reaction of current interest in biomass valorization. The products of this reaction, which is currently being performed on an industrial scale by means of ozonolysis, can be applied for the production of commodity chemicals such as plasticizers and polymers. Alternative, catalytic methods for this conversion that are not based on the hazardous ozone oxidant are of high interest. In this respect, the use of transition metal catalysts would allow the application of milder reaction conditions and more benign oxidants. This review covers the various transition metal-based catalysts that have been reported for the oxidative cleavage of alkenes in general and the cleavage of unsaturated fatty acids in particular. Catalytic systems based on second- and third-row metals such as Ru, Os, and W have been widely studied and are well-known to catalyze the cleavage of various alkenes and unsaturated fatty acids. In addition to simple metal salts, metal oxides or peroxides, various metal coordination complexes have been investigated for chemo- and regioselective olefin cleavage. Heterogeneous catalyst systems based on these metals have, in addition, been studied with a focus on catalyst reuse. To circumvent the use of expensive, toxic or less abundant second- and third-row metal catalysts, the use of first-row transition metal catalysts for the cleavage reaction might be preferred. However, examples of such catalysts for oxidative olefin cleavage are much less documented. The application of Fe- and Mn-based catalysts currently is largely limited to activated alkenes, e.g. styrene derivatives. The many possibilities that are offered by careful ligand design together with the recent advances in the field of first-row transition metal oxidation catalysis may allow for the development of catalyst systems that substitute ozone or second- and third-row metal catalysts for the oxidative cleavage of simple alkenes and unsaturated fatty acids.
    ChemInform 09/2014; 45(40). DOI:10.1002/chin.201440275
  • Rafael L. Oliveira · Jasper B. F. Hooijmans · Petra E. de Jongh · Robertus J. M. Klein Gebbink · Krijn P. de Jong ·
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    ABSTRACT: Pd nanoparticles were synthesized on nonfunctionalized and functionalized SBA-15 grafted with thiol or amine groups. The resulting materials were used as catalysts to study the influence of these functional groups for a similar Pd particle size of approximately 2 nm on the Heck reaction that uses iodide substrates. The nonfunctionalized catalysts lost their activity quickly because of Pd leaching and particle growth. However, if a mixed solvent that consisted of toluene and DMF was used and thiol groups were grafted on SBA-15, we were able to reduce the Pd leaching and particle growth to thus obtain a more stable catalyst in which an important role of the ligands was to recapture Pd. However, heterogeneity tests, such as a hot filtration test and poisoning experiments, gave a strong indication that Pd still leached from the support and that homogeneous Pd species were mainly responsible for the activity. Pd on S-functionalized SBA-15 was able to catalyze the Heck reaction using different substrates to achieve good activity and selectivity in most cases.
    ChemCatChem 09/2014; 6(11). DOI:10.1002/cctc.201402523 · 4.56 Impact Factor
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    ABSTRACT: Homogeneous metal complexes often display superior activity and selectivity in catalysis of chemical transformations. Heterogenization of these complexes by immobilization on solid supports has been used to facilitate recovery, but this is often associated with a decrease in catalytic performance. We here describe a novel approach of sizing and engineering the cavity structure of nanoporous materials as “nanoreactors” to assemble metal complexes by the “ship-in-the-bottle” synthesis to combine the best of homogeneous and heterogeneous catalysts. Catalysis occurred by free metal complexes in confined liquid in these nanoreactors, while the catalysts were recyclable as being heterogeneous at the macroscopic scale. Subnanometer tailoring of window sizes (0.5–3.7 nm) of the cavities (16–22 nm) allowed control over loading (6–70 mg-metal complex/g-support) and a high turnover frequency (40–600 h–1) for the hydrolytic kinetic resolution of 1,2-epoxyhexane. Most importantly, the ‘heterogeneous homogeneous catalysts’ showed enhanced thermal stability and were stable upon reuse approaching excellent turnover numbers of 100,000. We showed that engineering and sizing of nanoreactors is a powerful approach to control performance of confined catalysts, and this method is generally applicable in host–guest catalysis.
    ACS Catalysis 09/2014; 4(10):3791. DOI:10.1021/cs500777q · 9.31 Impact Factor

  • Organometallics 05/2014; 33(11):2914–2918. DOI:10.1021/om500005y · 4.13 Impact Factor
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    Martin Lutz · Yuxing Huang · Marc Etienne Moret · Robertus J. M. Klein Gebbink ·
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    ABSTRACT: The title compound, [(C2H5)4N][FeCl4], has at room temperature a disordered structure in the high-hexagonal space group P63mc. At 230 K, the structure is merohedrally twinned in the low-hexagonal space group P63. The volume has increased by a factor of 9 with respect to the room-temperature structure. At 170 and 110 K, the structure is identical in the orthorhombic space group Pca21 and twinned by reticular pseudomerohedry. The volume has doubled with respect to the room-temperature structure. All three space groups, viz. P63mc, P63 and Pca21, are polar and the direction of the polar axis is not affected by the twinning. In the P63 and Pca21 structures, all cations and anions are well ordered.
    Acta crystallographica. Section C 05/2014; 70(Pt 5):470-6. DOI:10.1107/S2053229614007955
  • Ties J. Korstanje · Martin Lutz · Johann T. B. H. Jastrzebski · Robertus J. M. Klein Gebbink ·
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    ABSTRACT: The synthesis of a series of pyridine-based PNP-pincer rhenium-oxo complexes, with phenyl (1, 3), tert-butyl (2), or cyclohexyl (4) groups on the phosphorus atoms and either a ReO2X (1, 2) or a ReCl2O (3, 4) core is reported. The structures of these compounds were characterized using 1H, 13C, and 31P NMR and using X-ray crystallography for 1 and 4. Compounds 2 and 3 crystallize as the corresponding ReO(OH)X compounds upon their reaction with moisture during the crystallization process. The complexes were tested as catalysts in the oxidation reaction of limonene with H2O2, the oxygen atom transfer reaction from pyridine N-oxide to triphenylphosphine, and the dehydration reaction of 1-phenylethanol, but all showed poor catalytic performance. All complexes can be deprotonated at the benzylic arm, and 2 can be deprotonated twice, accompanied by dearomatization of the pyridine ring. 3 and 4 are highly stable in their oxidized forms. The noninnocent behavior shown here could open up possibilities for cooperative catalysis.
    Organometallics 04/2014; 33(9):2201–2209. DOI:10.1021/om401228u · 4.13 Impact Factor
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    Peter Spannring · Vital Yazerski · Pieter C A Bruijnincx · Bert M Weckhuysen · Robertus J M Klein Gebbink ·
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    ABSTRACT: A one-pot method has been developed for the oxidative cleavage of internal alkenes into aldehydes by using 0.5 mol % of the nonheme iron complex [Fe(OTf)2 (mix-bpbp)] (bpbp=N,N'-bis(2-picolyl)-2,2'-bipyrrolidine) as catalyst and 1.5 equivalents of hydrogen peroxide and 1 equivalent of sodium periodate as oxidants. A mixture of diastereomers of the chiral bpbp ligand can be used, thereby omitting the need for resolution of its optically active components. The cleavage reaction can be performed in one pot within 20 h and under ambient conditions. Addition of water after the epoxidation, acidification and subsequent pH neutralization are crucial to perform the epoxidation, hydrolysis, and subsequent diol cleavage in one pot. High aldehyde yields can be obtained for the cleavage of internal aliphatic double bonds with cis and trans configuration (86-98 %) and unsaturated fatty acids and esters (69-96 %). Good aldehyde yields are obtained in reactions of trisubstituted and terminal alkenes (62-63 %). The products can be easily isolated by a simple extraction step with an organic solvent. The presented protocol involves a lower catalyst loading than conventional methods based on Ru or Os. Also, hydrogen peroxide can be used as the oxidant in this case, which is often disproportionated by second- and third-row metals. By using only mild oxidants, overoxidation of the aldehyde to the carboxylic acid is prevented.
    Chemistry - A European Journal 04/2014; 19(44). DOI:10.1002/chem.201301371 · 5.73 Impact Factor
  • Marcel A H Moelands · Daniel J Schamhart · Emma Folkertsma · Martin Lutz · Anthony L Spek · Robertus J. M. Klein Gebbink ·
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    ABSTRACT: A series of new chiral pyridinyl prolinate (RPyProR) ligands and their corresponding Fe(ii) triflate and chloride complexes are reported. The ligands possess an NN'O coordination motif, as found in the active site of non-heme iron enzymes with the so-called 2-His-1-carboxylate facial triad. The coordination behaviour of these ligands towards iron turned out to be dependent on the counter ion (chloride or triflate), the crystallization conditions (coordinating or non-coordinating solvents) and the presence of substituents on the ligand. In combination with Fe(ii)(OTf)2, coordinatively saturated complexes of the type [Fe(L)2](OTf)2 are formed, in which the ligands adopt a meridional coordination mode. The use of FeCl2 in a non-coordinating solvent leads to 5-coordinated complexes [Fe(L)(Cl)2] with a meridional N,N',O ligand. Crystallization of these complexes from a coordinating solvent leads to 6-coordinated [Fe(L)(solv)(Cl)2] complexes (solv = methanol or acetonitrile), in which the N,N',O ligand is coordinated in a facial manner. For RPyProR ligands bearing a 6-Me substituent on the pyridine ring, solvent coordination and, accordingly, ligand rearrangement are prevented by steric constraints. The complexes were tested as oxidation catalysts in the epoxidation of alkene substrates in acetonitrile with hydrogen peroxide as the oxidant under oxidant limiting conditions. The complexes were shown to be especially active in the epoxidation of styrene type substrates (styrene and trans-beta-methylstyrene). In the best case, complex [Fe(6-Me-PyProNH2)Cl2] () allowed for 65% productive consumption of hydrogen peroxide toward epoxide and benzaldehyde products.
    Dalton Transactions 03/2014; 43(18). DOI:10.1039/c3dt53266f · 4.20 Impact Factor

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