Renato Ugo

Organotin(IV) N,N-disubstituted dithiocarbamates

Compounds with general formulas R3Sn(SSCNR′2 (REt, Ph, R′) or R2Sn(SSCNR′2)2 (Rhalogen, Et, Ph; R′Et, Ph) were prepared and their physical data are reported and discussed. In X2SN(SSCNEt2)2 an octahedral cis coordination of the tin atom is shown to be present with a chelated dithiocarbamato moiety. A similar labile type of coordination seems to exist in solution for the corresponding organotin derivatives. In the case R3Sn(SSCNR′2), no sure evidence was found for or against the chelation of the dithiocarbamate moiety. A discussion as to what physical measurements actually serve as convincing criteria of structure and chelation in dithiocarbamates is presented.

Fundamental Research in Homogeneous Catalysis

During the 70s it has become drastically apparent that our natural resources, including energy, are not in unlimited supply. This realization is strongly felt in the economic turmoil that is occurring, but its effects will penetrate into other areas, even causing moderate social changes. Chemists playa major role in coverting the worlds natural resources into products. The public consumes these products and now depends upon them to keep the high standard of living to which they have become accustomed. This topic could easily be expounded into a whole article, but it is sufficent to say that almost everything-from the use of lightweight, strong polymers which are replacing the use of metals in todays automobiles, to the curing of diseases with asymetrically synthesized drugs-is related to the endeavors of chemistry. Catalysts have played a major role in transforming resources to useful products. Since a catalyst lowers the activation energy required for a particular reaction, and often for only one specific pathway where normally many exist, it is not surprising within the extant climate that researchers are now increasing their efforts and focusing their priorities on improving and discovering more efficient and selective catalysts.

Surface-supported metal cluster carbonyls. Chemisorption, decomposition and reactivity of Os3(CO)12, H2Os3(CO)10 and Os6(CO)18 supported on silica and alumina and the investigation of the fischer-tropsch catalysis with these systems

Abstract On silica and alumina, Os 3 (CO) 12 , H 2 Os 3 (CO) 10 and Os 6 (CO) 18 are physisorbed (or weakly adsorbed) at room temperature. When the physisorbed cluster Os 3 (CO) 12 is thermally decomposed at ca. 150°C, there is an oxidative addition of a surface MOH group (M  Al???, Si???) to the OsOs bond of Os 3 (CO) 12 with formation of the surface species Os 3 (H)(CO) 10 (OM) (M  Al???, Si???) in which the cluster is covalently bonded to the surface by MOOs 3 bonds.Such a grafted cluster was also obtained was also obtained by bringing Os 3 (CO) 10 (CH 3 CN) 2 or H 2 Os 3 (CO) 10 into reaction with the surface of silica and alumina. On silica the grafted cluster, when treated with CO + H 2 O, can regenerate the starting Os 3 (CO) 12 cluster. The structure of the covalently bonded cluster was also confirmed by the synthesis of the model compound Os 3 (H)(CO) 10 (OSi(Ph) 3 ). Such covalent attachment of a cluster to a surface can be regarded as a model for the metal—support interaction which is frequently involved in heterogeneous catalysis. When the physisorbed clusters Os 3 (CO) 12 , H 2 Os 3 (CO) 10 , Os 6 (CO) 18 or the chemisorbed cluster Os 3 (H)(CO) 10 (OM), (M  Al???, Si???), are heated at about 200°C, there is a breakdown of the cluster cage with simultaneous oxidation of the osmium to two osmium(II) carbonyl species by the surface proton with simultaneous release of hydrogen. The [Os II (CO) 3 X 2 ] 2 and [Os II (CO) 2 X 2 ] n surface species in which X is a surface oxygen atom can be interconverted by a reversible carbonylation-decarbonylation process at 200°C. These two species can be also obtained by decomposition of [Os(CO) 3 X 2 ] 2 , (X  Cl, Br) onto silica or alumina surface or by CO reduction at 200°C of OsX 3 adsorbed on silica or alumina. The structure of one these surface compounds was confirmed by synthesis of the model compound [Os(CO) 3 (OSiPh 3 ) 2 ] m . These surface osmium carbonyl species exhibit a rather high thermal and chemical stability. They appear to be reduced by H 2 to metallic osmium only at 400°C. The thermal decomposition of the supported clusters is followed by a stoichiometric water gas shift reaction as well as a stoichiometric formation of methane. Under CO + H 2 , a Fischer-Tropsch catalyst, which exhibits a high selectivity for methane, is obtained. From the range of temperatures over which those stoichiometric and catalytic reactions are observed it seems reasonable to assume that they involve the Os II carbonyl species rather than metallic osmium.

Modern Surface Organometallic Chemistry

Preface ON THE ORIGINS AND DEVELOPMENT OF ?SURFACE ORGANOMETALLIC CHEMISTRY? The Basic Concept Use of Probe Molecules on Metallic Surfaces as Evidence of Coordination and Organometallic Chemistry at Metal Surfaces Chemical and Structural Analogy between Molecular Clusters and Small Metallic Particles Analogy between Supported Molecular Clusters and Small Supported Catalytic Particles Foundation of Surface Organometallic Chemistry From Organometallic Surface Chemistry to the Elementary Steps Occurring on Surfaces and Stabilization by the Surface of Rather Unstable Molecular Species From Surface Organometallic Chemistry on Oxides to Surface Organometallic Chemistry on Metals From Surface Organometallic Chemistry to Surface-Mediated Organometallic Synthesis Single Metal Site Heterogeneous Catalysts and the Design of New Catalysts PREPARATION OF SINGLE SITE CATALYSTS ON OXIDES AND METALS PREPARED VIA SURFACE ORGANOMETALLIC CHEMISTRY Introduction Surface Organometallic Chemistry on Oxides Reaction of Organometallic Compounds with Supported or Unsupported Group VIII Metals Particles Conclusion CATALYTIC PROPERTIES OF SINGLE SITE CATALYSTS PREPARED VIA SURFACE ORGANOMETALIC CHEMISTRY ON OXIDES AND ON METALS Introduction Stoichiometric Activation of Alkane C-H Bonds Alkane C-C Bond Activation by Tantalum Hydrides. Low Temperature Catalytic Hydrogenolysis of Alkanes Metathesis of Acyclic Alkanes Cross-Metathesis Reactions of Alkanes Homologation of Alkanes Polystyrene Modification and Hydrogenolysis of Linear Alkanes and Polyethylene by a Supported Zirconium Hydride Olefin Metathesis Olefin Epoxidation Deperoxidation of Cyclohexyl Hydroperoxide Some Applications of Supported Nanoparticles Modified by Organometallics Conclusion BUILDING BLOCK APPROACHES TO NANOSTRUCTURED, SINGLE SITE, HETEROGENEOUS CATALYSTS Introduction Current Challenges in Catalysis What is a Nanostructured Catalyst? Benefits of Nanostructuring Catalysts Current Approaches to Nanostructured Catalysts Building Block Approaches to Nanostructured Materials and Catalysis Nanostructured Catalysts via a Non-Aqueous Building Block Methodology A Model for the Growth of Building Block Matrices and a Nanostructuring Strategy A General Procedure for Preparing Nanostructured Catalysts in Silicate Matrices Atomically Dispersed Titanium and Vanadium, Single Site Catalysts Bridge between Nanostructuring and Catalysis Summary TRANSITION METAL SINGLE SITE CATALYSTS ? FROM HOMOGENEOUS TO IMMOBILIZED SYSTEMS Introduction Covalently Anchored Organometallic Complexes on Unmodified Silica Anchoring of Organometallic Complexes via the Metal Center Organometallic Complexes Anchored via a Covalent Linkage to a Ligand Noncovalently Anchored Organometallic Complexes Encapsulated Organometallic Complexes Conclusions CONTROLLED PREPARATION OF HETEROGENEOUS CATALYSTS FOR CHEMO- AND ENANTIOSELECTIVE HYDROGENATION REACTIONS Introduction Catalyst Preparation and Characterization Hydrogenation of Alpha,Beta-Unsaturated Aldehydes Hydrogenation of Aromatic Ketones Enantioselective Hydrogenation Reactions Conclusions WELL-DEFINED SURFACE RHODIUM SILOXIDE COMPLEXES AND THEIR APPLICATION TO CATALYSIS Molecular versus Immobilized Transition Metal Siloxide Complexes in Catalysis Synthesis, Characterization and Catalytic Activity of Well-Defined Surface Rhodium Siloxide Complexes Solid-State NMR Method in Catalysis by Surface Organometallics Mechanism of Hydrosilylation Catalyzed by Surface versus Soluble Rhodium Siloxide Complexes CARBONYL COMPOUNDS AS METALLIC PRECURSORS OF TAILORED SUPPORTED CATALYSTS Introduction Catalysts Prepared from Metal Carbonyls of Groups 6, 7, 10 and Gold Catalysts Prepared from Metal Carbonyls of Group 8: Iron, Ruthenium and Osmium Catalysts Prepared from Metal Carbonyls of Group 9: Cobalt, Rhodium and Iridium Concluding Remarks EXPLOITING SURFACE CHEMISTRY TO PREPARE METAL-SUPPORTED CATALYSTS BY ORGANOMETALLIC CHEMICAL VAPOR DEPOSITION Introduction Surface Organometallic Chemistry Strategies to Avoid the Contamination of Metal Deposits How to Manage the Nucleation and Growth Steps Concluding Remarks ADVANCED DESIGN OF CATALYST SURFACES WITH METAL COMPLEXES FOR SELECTIVE CATALYSIS Introduction Isolation and Epoxidation Activity of a Coordinatively Unsaturated Ru Complex at a SiO2 Surface Chiral Self-Dimerization of V Complexes on a SiO2 Surface for Asymmetric Catalysis Molecular Imprinting Rh-Dimer and Rh-Monomer Catalysts Re Clusters in HZSM-5 Pores for Direct Phenol Synthesis Conclusion SURFACE ORGANOMETALLIC CHEMSITRY OF D(0) METAL COMPLEXES Introduction Ligands Susceptible to React with Hydroxyl Groups of an Inorganic Oxide Ligands Susceptible to Reaction with Lewis Acid Sites of Inorganic Oxides Reactivity of Hydrocarbyl-Metal Complexes and the Metal Atom Inorganic Oxides as Supports for Organometallic Species Models for Surface Organometallic Species Tuning the Catalytic Activity of Surface Organometallic Species Relevant Aspects of the Full Characterization of Some Selected Species Concluding Remarks SURFACE ORGANOLANTHANIDE AND ?ACTINIDE CHEMISTRY Introduction Surface Organolanthanide Chemistry SOLnC Surface Organoactinide Chemistry, SOAnC Catalytic Applications of SOLnC and SOAnC Conclusions and Perspectives ISOCYANIDE BINDING MODES ON METAL SURFACES AND IN METAL COMPLEXES Introduction Modes of Isocyanide Coordination in Transition Metal Complexes Adsorption of Isocyanides (C=N-R) on Metal Surfaces Conclusions MOLECULAR INSIGHT FOR SILICA-SUPPORTED ORGANOMETALLIC CHEMISTRY THROUGH TRANSITION METAL SILESQUIOXANES Introduction Organometallic POSS Derivatives Conclusions SURFACE-MEDIATED NANOSCALE FABRICATION OF METAL PARTICLES AND WIRES USING MESOPOROUS SILICA TEMPLATES AND THEIR SHAPE/SIZE DEPENDENCY IN CATALYSIS Introduction Surface-Mediated Synthesis of Metal/Alloy Nanowires Using Mesoporous Templates Characterization of Nanowires and Nanoparticles in FSM-16 and HMM-1 Mechanism for Formation of Pt Nanowires in Mesoporous Silica Templates Isolation and Characterization of Metal/Alloy Nanowires Free from the Silica Supports Novel Surface-Mediated Fabrication of Rh and RhPt Nanoparticles Using Mesoporous Templates in Supercritical Carbon Dioxide Other Surface-Mediated Synthesis of Metal Nanowires on Porous Membrane and Graphite Steps Shape/Size Dependency in Catalysis of Metal/Alloy Nanowires and Particles in Mesoporous Silica Templates Synthesis of Pt and Au Nanoparticle Arrays in Mesoporous Silica Films and their Electric/Magnetic Properties in Terms of the Quantum-Size Effect Conclusion SURFACE-MEDIATED ORGANOMETALLIC SYNTHESES Introduction Group 7: Rhenium Group 8 Group 9 Group 10 Conclusion

Surface supported metal cluster carbonyls. Chemisorption decomposition and reactivity of Rh4(CO)12 supported on silica and alumina

Abstract Chemisorption of Rh 4 (CO) 12 on to a highly divided silica (Aerosil “0” from Degussa), Leads to the transformation: 3 Rh 4 (CO) 12 → 2 Rh 6 (CO) 16 + 4 CO. Such an easy rearrangement of the cluster cage implies mobility of zerovalent rhodium carbonyl fragments on the surface. Carbon monoxide is a very efficient inhibitor of this reaction, and Rh 4 (CO) 12 is stable as such on silica under a CO atmosphere. Both Rh 4 (CO) 12 and Rh 6 (CO) 16 are easily decomposed to small metal particles of higher nuclearity under a water atmosphere and to rhodium(I) dicarbonyl species under oxygen. From the Rh I (CO) 2 species it is possible to regenate first Rh 4 (CO) 12 and then Rh 6 (CO) 16 by treatment with CO ( P co ⩾ 200 mm Hg) and H 2 O ( P H 2 O ⩾ 18 mm Hg). The reduction of Rh I (CO) 2 surface species by water requires a nucleophilic attack to produce an hypothetical [Rh(CO) n ] m species which can polymerize to small Rh 4 or Rh 6 clusters in the presence of CO but which in the absence of CO lead to metal particles of higher nuclearity. Similar results are obtained on alumina.

Surface-supported metal cluster carbonyls. Chemisorption, decomposition and reactivity of Rh6(C0)16 supported on silica

Abstract A partially decarbonylated metal cluster is quickly formed on the surface of silica by oxidation at room temperature; it is possible to regenerate the initial cluster compound under a carbon monoxide atmosphere at 200°C. Decarbonylation of Rh 6 (CO) 16 at higher temperature produces a new metallic material on the surface, characterized by two v (CO) vibration bands at 2048 ± 7 cm −1 and 1893 ± 10 cm −1 . These two bands have been respectively assigned to a terminal carbonyl group and a bridged carbonyl group bonded to two rhodium atoms. Oxidation of this compound occurs very easily under oxygen at room temperature and gives an oxidized material presumably of the same nuclearity; adsorption of carbon monoxide produces two intense sharp bands at 2093 and 2038 cm −1 which have been assigned to the symmetric and asymmetric stretching modes of two CO molecules bonded to a single oxidized Rh site as Rh I (CO) 2 . The conversion from the oxidized surface species to the metallic one can be performed under mild conditions, but attempts to regenerate the initial cluster compound were unsuccessful.

Organotin and organothallium ditiophosphinates and dithiocarbamates

Compounds with general formula R2Tl(SSPR′2), R2Sn(SSPR′2)2, R3Sn(SSPR′2), X2Sn(SSPR′2)2, R2Tl(SSCNR″2 were prepared (R = methyl, ethyl, phenyl; X = chlorine, bromine; R′ = ethyl, phenyl; R

Cyclometallated platinum(II) complexes of 1,3-di(2-pyridyl)benzenes: tuning excimer emission from red to near-infrared for NIR-OLEDs

= methyl, ethyl, phenyl). The dithiocarbamato derivatives appear to be chelated and monomeric in solution with a four-coordinate thallium(III). Tl(SSCNEt2)3 was found to be six-coordinate in solution. The dithiophosphinates were found to be associated in solution and possible explanation for this are discussed Owing to the presence of association, the assignment of cis or trans structure to X2Sn(SSPR′2)2 or R2Sn(SSPR′2)2 compounds is difficult.

Homogeneous catalysis by transition metal complexes I. The homogeneous cyclohexene oxidation catalysed by low valent tertiary phosphine-transition metal complexes

The Pt(II) complex N^C2^N-1,3-di(2-pyridyl)benzene platinum chloride (PtL1Cl) is known to display efficient triplet luminescence in the green region of the spectrum, and to form an unusually emissive excimer that emits around 690 nm. In this contribution, the introduction of trifluoromethyl groups into either the 4- or 5-position of the pyridyl rings of the ligand is shown to lead to a red-shift in the excimer band, moving it into the near infra-red (NIR) region. The new ligands, synthesised by either Suzuki or Stille cross-coupling methods, are 1,3-bis(4-(trifluoromethyl)pyridin-2-yl)benzene HL27, 1,3-bis(4-(trifluoromethyl)pyridin-2-yl)-4,6-difluorobenzene HL28, and 1,3-bis(5-(trifluoromethyl)pyridin-2-yl)-4,6-difluorobenzene HL29, from which the corresponding Pt(II) complexes PtLnCl have been prepared. The monomer and excimer emission energies in solution are compared with those of PtL1Cl and PtL22Cl {HL22 = 1,3-di(2-pyridyl)-4,6-difluorobenzene}. The order for the monomer can be rationalised in terms of the stabilising effects of the F atoms and the CF3 groups on the HOMO and LUMO respectively. The order of excimer emission proves to be subtly different, but the most red-shifted complex in both cases is PtL27Cl. The electroluminescence of neat films of the complexes as emitting layers in OLEDs displays uniquely excimer-like emission, extending well into the technologically important NIR region.

Coordination and Organometallic Complexes as Second-Order Nonlinear Optical Molecular Materials

Abstract The oxidation of cyclohexene catalysed by low oxidation state phosphine-transition metal complexes has been studied at 65° and 1 atm of oxygen. The process is a radical reaction but no marked oxygen activation promoted by coordination on the transition metal is usually involved, and the effective action of transition metal complexes is related to their interaction with performed cyclohexene hydroperoxide to form radicals. Only in few cases is oxygen activation probably involved.