Marta Iglesias

Homogeneous and heterogenized Au(III) Schiff base-complexes as selective and general catalysts for self-coupling of aryl boronic acids

A series of homogeneous and heterogenized gold metal complexes show high activity and selectivity for the homocoupling of a large variety of aryl boronic acids, being of general utility for the synthesis of C2-symmetric biaryls.

Optically active complexes of transition metals (RhI, RuII, CoII and NiII) with 2-aminocarbonylpyrrolidine ligands. Selective catalysts for hydrogenation of prochiral olefins

Abstract The synthesis and characterization of optically active complexes containing organic amides [-C(O)NHR] of the type [RhCl(COD) L ], [RhCl(CO) 2 L ], [RhCl(PPh 3 ) 2 L ], [RuCl 2 (COD) L ], [RuCl 2 (PPh 3 ) 2 L ], [Co(acac) L ]X and [Ni(acac) L ]X, where L = ( S )-2- t -butylaminocarbonylpyrrolidine or ( S )-2-(3-triethoxysilyl)propylaminocarbonylpyrrolidine are reported. Their cationic species were prepared in the presence of a non-coordinating counterion (X = PF 6 − or ClO 4 − ). The amino acid derivative is bi-dentate with N,N -coordination. The metal complexes with ligands containing the triethoxysilyl group, were anchored to silica and modified USY-zeolite. These complexes have been characterized by spectroscopic and analytical techniques. The complexes anchored to the zeolite, which contains profuse supermicropores, show a higher activity for alkene hydrogenation and produce a remarkable increase of enantioselectivity ( > 95%) in the hydrogen ation of ethyl ( Z )-α-benzoylaminocinnamate, taken as a model, and they represent a truly heterogeneous counterpart of the homogeneous organometallic catalysts.

Reversible Breaking and Forming of Metal–Ligand Coordination Bonds: Temperature‐Triggered Single‐Crystal to Single‐Crystal Transformation in a Metal–Organic Framework

Yb(C(4)H(4)O(4))(1.5)] undergoes a temperature-triggered single-crystal to single-crystal transformation. Thermal X-ray single-crystal studies showed a reversibly orchestrated rearrangement of the atoms generated by the breaking/formation of coordination bonds, in which the stoichiometry of the compound remains unchanged. The transformation occurs on heating the crystal at approximately 130 degrees C. This uncommon behavior was also studied by thermal methods, FTIR spectroscopy, and thermodiffractometry. Both polymorphs, alpha (room-temperature form) and beta (high-temperature form), are proven to be active heterogeneous catalysts; the higher catalytic activity of beta is owed to a decrease in the Yb coordination number. A mechanism based on spectroscopic evidence and involving formation of the active species Yb-O-OH is proposed for the sulfide oxidation.

Cu and Au Metal–Organic Frameworks Bridge the Gap between Homogeneous and Heterogeneous Catalysts for Alkene Cyclopropanation Reactions

The copper and gold metal-organic frameworks (MOFs) [Cu(3)(BTC)(2)(H(2)O)(3)](n), [Cu(3)(BTC)(2)] (BTC=benzene-1,3,5-tricarboxylate), and IRMOF-3-SI-Au are active and reusable solid catalysts for the cyclopropanation of alkenes with high chemo- and diastereoselectivities. This type of material gives better results than previous solid catalysts while working together with the homogeneous catalysts. These MOFs can help to bridge the gap between homogeneous and heterogeneous catalysis.

Large pore Ti-zeolites and mesoporous Ti-silicalites as catalysts for selective oxidation of organic sulfides

The oxidation of bulky thioethers has been carried out on Ti-Beta and Ti-MCM-41 catalysts, using H2O2 andt-butyl hydroperoxide (TBHP) as oxidants. The intrinsic activity of Ti-Beta was higher than that of Ti-MCM-41 for the oxidation of methyl phenyl sulfide which can penetrate in the pores of Beta, while in the case of the larger isopentyl phenyl sulfide, which diffuses more slowly in Ti-Beta zeolite, Ti-MCM-41 gives a larger activity. Ti-Beta is able to perform better for the more demanding oxidation of sulfoxides to sulfones giving, therefore, higher selectivities to sulfones than Ti-MCM-41. Similar results were obtained when using either H2O2 or TBHP as oxidants. However, the sterical effects were enhanced when TBHP was used as oxidant.

Lanthanide Metal–Organic Frameworks: Searching for Efficient Solvent-Free Catalysts

Three Ln-based 2D metal-organic frameworks with the formula [Ln(3,5-DSB)(Phen)] (Ln = La, Pr, Nd; 3,5-DSB = 3,5-disulfobenzoate; Phen = 1,10-phenathroline) were hydrothermally synthesized. They belong to two 2D structural types, and their nets own different topologies. The isostructural La and Pr compounds possess a uninodal 5-connected SP 2-periodic net (6,3). The Nd compound has a binodal 3- and 6-connected kgd net. The novel compounds exhibit excellent catalytic activities toward the cyanosilylation reaction under solvent-free conditions.

New rhodium complexes anchored on modified USY zeolites. A remarkable effect of the support on the enantioselectivity of catalytic hydrogenation of prochiral alkenes

Rh-complexes with N-based chiral ligands, when anchored on a modified USY-zeolite which contains profuse supermicropores, produce a remarkable increase of enantioselectivity (>95%) in the hydrogenation of N-acyldehydrophenylalanine derivatives and represent a truly heterogeneous counterpart of the homogeneous organometallic catalysts.

Rare-earths as catalytic centres in organo-inorganic polymeric frameworksElectronic supplementary information (ESI) available: selected bond angles and hydrogen interactions in 1, 2, 3; coordination environment of the two scandium atoms in 1; coordination modes of the three crystallographically independent carboxylate groups for 2 and 3. See http://www.rsc.org/suppdata/jm/b3/b314220e/

New 3D polymeric succinates of rare-earths have been synthesised: [Sc2(C4H4O4)2.5(OH)], [Y2(C4H4O4)3(H2O)2]·H2O, [La2(C4H4O4)3(H2O)2]·H2O, and their structures solved by single crystal XRD. They were obtained as single phases, characterised and tested as heterogeneous catalysts as Lewis acids in the acetalization of aldehydes and as redox agents in the oxidation of sulfides showing them to be effective and selective catalysts, easy to recover and reusable. The scandium, yttrium and lanthanum oxides were also tested in the same catalytic reactions to prove the effect of the porous organo-inorganic framework.

Preparation of new chiral dioxomolybdenum complexes heterogenised on modified USY-zeolites efficient catalysts for selective epoxidation of allylic alcohols

Abstract A series of dioxomolybdenum(VI) complexes were synthesised by reaction of Mo(VI) complexes with new chiral ligands derived from (2S,4R)-4-hydroxyproline. The complexes bearing a Si(OEt)3 group were heterogenised to a modified USY-zeolite by covalent bonding. All catalysts, homogeneous and heterogenised, are active and regioselective in the epoxidation of allylic alcohols at room temperature using tert-butyl hydroperoxide as terminal oxidant. The catalytic activity of the heterogenised complexes is generally comparable with the corresponding homogeneous ones, yielding epoxyalcohols with excellent yields and selectivity and moderate enantioselectivity. Life time of heterogenised catalysts has been examined by repeated use of the complexes leading similar rates and yields of epoxide, whilst no appreaciable loss of metal has been observed over several runs.

Tunable Catalytic Activity of Solid Solution Metal–Organic Frameworks in One-Pot Multicomponent Reactions

The aim of this research is to establish how metal-organic frameworks (MOFs) composed of more than one metal in equivalent crystallographic sites (solid solution MOFs) exhibit catalytic activity, which is tunable by virtue of the metal ions ratio. New MOFs with general formula [InxGa1-x(O2C2H4)0.5(hfipbb)] were prepared by the combination of Ga and In. They are isostructural with their monometal counterparts, synthesized with Al, Ga, and In. Differences in their behavior as heterogeneous catalysts in the three-component, one pot Strecker reaction illustrate the potential of solid solution MOFs to provide the ability to address the various stages involved in the reaction mechanism.