Oriol Rossell

A general approach to fabricate fe3O4 nanoparticles decorated with Pd, Au, and Rh: Magnetically recoverable and reusable catalysts for Suzuki C-C cross-coupling reactions, hydrogenation, and sequential reactions

A facile strategy has been explored for loading noble metals onto the surface of ferrite nanoparticles with the assistance of phosphine-functionalized linkers. Palladium loading is shown to occur with participation of both the phosphine function and the surface hydroxyl groups. Hybrid nanoparticles containing simultaneously Pd and Au (or Rh) are obtained by successive loading of metals. Similarly, ferrite nanoparticles decorated with Pd, Au, and Rh have also been formed by using the same strategy. The catalytic properties of the new nanoparticles are evidenced in processes such as reduction of 4-nitrophenol or hydrogenation of styrene. Besides, the sequential process involving a cross-coupling reaction followed by reduction of 1-nitrobiphenyl has been successfully achieved by employing Pd/Au decorated nanoferrite particles.

Carbosilane dendrimers functionalized with AuFe3 clusters

Abstract The reaction of the carbosilane dendrimers Si(CH 2 CH 2 SiMe 3− n Cl n ) 4 ( n =1,2) with LiCH 2 PPh 2 afforded the new phosphino-terminated dendrimers Si(CH 2 CH 2 SiMe 2 CH 2 PPh 2 ) 4 ( 1 ) and Si(CH 2 CH 2 SiMe(CH 2 PPh 2 ) 2 ) 4 ( 2 ). By treatment of 1 and 2 with ClAu(tht), the gold-containing dendrimers Si(CH 2 CH 2 SiMe 2 CH 2 PPh 2 AuCl) 4 ( 3 ) and Si(CH 2 CH 2 SiMe(CH 2 PPh 2 AuCl) 2 ) 4 ( 4 ) were obtained, which in turn, reacted with (PPh 4 ) 2 [Fe 3 (CO) 11 ] to give the first metal-cluster-containing dendrimers reported so far: (PPh 4 ) 4 [Si(CH 2 CH 2 SiMe 2 CH 2 PPh 2 {AuFe 3 (CO) 11 }) 4 ] ( 5 ) and (PPh 4 ) 8 [Si(CH 2 CH 2 SiMe(CH 2 PPh 2 {AuFe 3 (CO) 11 }) 2 ) 4 ] ( 6 ).

Gold-Containing Dendrimers: A New Class of Macromolecules

The synthesis of dendrimers possessing gold atoms on the surface or inside the internal layers is reported. They have been shown to be precursors to mixed gold-transition metal cluster-containing dendrimers, which represent a new class of hybrid materials. The latter species are rather soluble in common solvents and can be characterized by spectroscopic methods. Moreover, gold-containing dendrimers are useful for making gold nanoparticles, which have very interesting electronic, optical, and catalytic properties.

Anionic and neutral spiked triangle clusters of mercury : a comparative study of the metal ligand redistribution process

Abstract The action of the NEt + 4 salts of the anions [Fe 2 (CO) 8 ] 2− and [Fe 2 (CO) 6 (μ-CO)(μ-PPh 2 )] − on ClHg-m complexes (m = Mo(CO) 3 Cp, W(CO) 3 Cp, Mn(CO) 5 , Co(CO) 4 , and Fe(CO) 2 Cp) has been investigated. In the first case, anionic spiked triangle clusters of formula [Fe 2 (CO) 6 (μ-CO) 2 (μ-Hg-m)] − were obtained in high yields, and no metal ligand redistribution reactions were detected. However, the action of [Fe 2 (CO) 6 (μ-CO)(μ-PPh 2 )] − on the same bimetallic transition metal-mercury compounds gave the neutral species [Fe 2 (CO) 6 (μ-CO)(μ-PPh 2 )(μ-Hg-m)], which spontaneously redistributed to [Hg{Fe 2 (CO) 7 (μ-PPh 2 )} 2 ] and m 2 Hg. Only the molybdenum derivative could be isolated in pure form. The different behaviour of the two series of complexes in the redistribution process is discussed.

Highly dispersed cobalt in CuCo/SiO2 cluster-derived catalyst

Abstract A silica-supported CuCo catalyst has been prepared by anchoring a Cu–Co bimetallic complex. Evolution of the species under vacuum and CO treatments has been followed by in situ FTIR. A breakdown of the initial complex with CO at 373 K gives [Co(CO) 4 ] − . After total decarbonylation, a subsequent CO treatment followed by FTIR indicates the presence of metallic Cu and very small particles of cobalt. The catalyst obtained after an H 2 -treatment at 473 K has been characterized by XRD, TEM and XPS techniques. The presence of large Cu particles and highly-dispersed subnanometric cobalt particles is inferred. Coordination of CO on these very small particles of metallic cobalt could give Co 4 (CO) 12 . Catalytic behaviour in the hydroformylation of ethylene and in the hydrogenation of CO is related to the highly dispersed cobalt, which probably interacts with Cu. An easy CO insertion into a metal–alkyl bond is favoured over this CuCo catalyst.

Anionic trimetallic compounds containing FeEM skeletons (E = Zn, Cd, Hg; M = Fe, Mo, W). Crystal structure of [N(PPh3)2]2[(OC)4FeHgFe(CO)4]

Dichlorides of group 12 elements react with (NEt4)[HFe(CO)4] in tetrahydrofuran to give the di-hydrides [(OC)4HFeEFeH(CO)4] (E = Zn, Cd, Hg) in good yields. These compounds undergo proton abstraction by nBuLi to give di-anions [(OC)4FeEFe(CO)4]2-, stabilized as their bis(triphenylphosphine)nitrogen(+) (PPN+) salts. (PPN)2[(OC)4FeHgFe(CO)4] crystallizes in the triclinic system, space group P1 with a 20.382(3), b 15.328(2), and c 13.420(2) A; α 115.96(3), β 108.89(2), and γ 87.09(2)o, and Z = 2. The anion consists of an almost linear spine (FeHgFe angle 178.7(1)o), with an average FeHg bond distance of 2.546(2) A. The Fe atoms display a trigonal bipyramidal geometry, and the equatorial CO groups linked to the iron atoms are in an eclipsed conformation, resulting in an idealized D3h symmetry. The existence of two conformers for this anion and the presence of Hg · · · CO backbonding are discussed on the basis of qualitative molecular orbital theory. The [(OC)4FeHgFe(CO)4]2- anion undergoes redistribution reactions with [M(CO)3(η-C5H5)]2 Hg (M = Mo, W) to give the new unsymmetrical anions [(OC)4FeHgM(CO)3(η-C5H5)]-.

Anionic iron clusters as building blocks for the synthesis of higher nuclearity compounds containing 11- and 12-group elements

Abstract Anionic iron clusters have been widely used as building blocks for the formation of mixed metal clusters with 11- and 12- group elements. This review summarizes the results reported in this area, paying special attention to the structural features of the metal core of the species reported.

Study of the self-assembly reactions between the organic linker 1,4-bis(4-pyridyl)butadiyne and the metal-containing corners (diphosphine)M(II) (M=Pd, Pt; diphosphine=dppp, dppf, depe, dppbz)

Abstract The diaza ligand 1,4-bis(4-pyridyl)butadiyne ( L ) has been used as a linker in self-assembly reactions with different diphosphine Pd(II) and Pt(II) triflates to build metallosupramolecular squares and triangles. Equilibria between triangular and square entities have been detected in most of the cases and their composition studied by multinuclear NMR spectroscopy and mass spectrometry. The self-assembly process has been shown to be strongly dependent on the conditions of the medium and the nature of the transition metal. The ability of some of these compounds to recognise inorganic anions has been investigated.

Electrospray mass spectrometric studies of some heterometal anionic carbonyl clusters

Electrospray mass spectra (ESMS) are reported for a series of anionic transition-metal clusters of the type (PPh4)[Fe3(CO)10(μ-CO){μ-Hg(m)}] (m = Mo(CO)3Cp; Co(CO)4; Fe(CO)2Cp; W(CO)3Cp; Mn(CO)5) and also for the species of higher nuclearity (NEt4)[Fe6C(CO)16AuPPh3] in methanol solution. The results were compared with those obtained by FAB-MS, and they indicate that ESMS is the most appropriate technique by which to obtain control fragmentation. Information about the strength of the different metal-metal bonds present in the cluster can be deduced from the species generated.

A comparative study of the use of triethylammonium salts of the [Fe2(CO)6(μ-CO)(μ-SR)]− anion in the synthesis of iron-gold clusters. Crystal structures of [Fe2(CO)6(μ-CO)(μ-SiPr)(μ-AuPPh3)] and [Fe2(CO)5(PPh3)(μ-SEt)2]

Abstract Salts of the type (NEt3H)[Fe2(CO)6(μ-CO)(μ-SR)] (R=1cr; iPr, tBu, Ph) react with [ClAuPPh3] in the presence of TIBF4 to produce the neutral iron-gold clusters [Fe2(CO)6(μ-CO)(μ-SR)(μ-AuPPh3)] (R=1cr; iPr, 1; R=1cr; tBu, 2; R=1cr; Ph, 3) in high yields. The structure of 1 has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P21/c, with a = 11.373(1), b = 14.899(3), c = 17.997(8) A, β = 95.12(2)° and Z = 4, R = 0.030 and R′ = 0.035 for 3579 unique reflections with I ⩾ 2σ(I). The basic skeleton consists of an Fe2Au triangle where the FeFe bond is bridged by a carbonyl and a thiolate group. In contrast, the reaction of the salts (NEt3H)[Fe2(CO)6(μ-CO)(μ-SR)] (R = Et or C6F5) with [ClAuPPh3] does not afford the corresponding mixed iron-gold clusters, and the diiron mono- or di-substituted complexes [Fe2(CO)5 (PPh3)(μ-SR)2] (R=1cr; Et, 4; R=1cr; C6F5, 5) and [Fe2(CO)4(PPh3)2(μ-SEt)2] (6) are obtained instead. The structure of 4 has been established by single-crystal X-ray diffraction studies. Crystals are triclinic, space group, P 1 , with a = 10.472(4), b = 11.329(2), c = 13.437(2) A, α = 80.34(2), β = 92.62(3), γ = 114.46(2)°, and Z = 2, R = 0.027 and R′ = 0.030 for 3732 unique reflections with I ⩾ 2σ(I). The FeFe bond in 4 is almost symmetrically double-bridged by two thiolate ligands and the phosphine group attached to the Fe(1) is trans to the iron-iron bond.