Attempts to synthesize Au–Pd heterometallic compounds from homonuclear palladium or gold complexes, [Pd(PtBu 2 ) 2 ] and [Au(PPh 3 )Cl] in a tetrahydrofuran (THF) solution under a CO atmosphere resulted in a homonuclear Pd cluster, namely pentakis(μ-carbonyl-κ 2 C : C )tetrakis(triphenylphosphane-κ P )tetrapalladium(5 Pd — Pd ) tetrahydrofuran disolvate, [Pd 4 (CO) 5 (C 18 H 15 P) 4 ]·2C 4 H 8 O. The complex molecule lies on a twofold rotation axis. The crystal structure is described in relation to the CH 2 Cl 2 solvate previously determined by our group [Willocq et al. (2011). Inorg. Chim. Acta , 373 , 233–242], and in particular to the desolvated structure [Feltham et al. (1985). Inorg. Chem. 24 , 1503–1510]. It is assumed that the title compound transforms into the latter structure, upon gradual loss of solvent molecules. In the title compound, the symmetry-unique THF solvent molecule is linked to the complex molecule by a weak C—H...O hydrogen bond. Contributions of disordered solvent molecules to the diffraction intensities, most likely associated with methanol, were removed with the SQUEEZE [Spek (2015). Acta Cryst. C 71 , 9–18] algorithm.

Molecular phosphine–carbonyl palladium clusters were anchored onto a phosphine-functionalized carbon support (CPPh2) by ligand exchange. This support was characterized by solid-state NMR prior to reaction with the clusters. The same clusters were also deposited on the non-functionalized support (CSX+). Characterization by SEM and XPS showed that the surface was more uniform when using the functionalized support. After thermal activation, the Pd/C materials obtained were characterized by CO chemisorption, XPS, SEM, TEM, powder XRD and analyzed for metal loading by ICP-OES. Again, the solids prepared with the functionalized support presented a more uniform surface. TEM indicated that small nanoparticles (1–10nm) were present on the surface with narrow size distributions. The activated Pd/C materials proved to be efficient catalysts for the hydrogenation of nitrobenzene into aniline. They were competitive with commercial and literature catalysts. Moreover, the catalysts prepared using the functionalized support were more active and more stable than when using CSX+.

Two mixed-metal clusters, [Ru5PtC(CO)(14)(COD)] (1) and [Ru6Au2C(CO)(16)(PPh3)(2)] (2), were anchored onto a prefunctionalized active carbon support (C-PPh2) with chelating phosphane groups on its surface. These clusters were also deposited onto the unmodified support (CSX+) for comparison. The incorporation of 1 and 2 on both supports was studied by a combination of SIMS and XPS. When the clusters were anchored onto the functionalized carbon support, SIMS spectra displayed characteristic patterns that were different from those obtained in the case of their deposition on the unmodified support. In the latter case, spectra corresponded to the results obtained with pure unsupported clusters. XPS analyses of the supported species seemed to indicate that the stoichiometry of the clusters was retained after anchoring and that their dispersion was better on C-PPh2 than on CSX+. This indicates that the phosphanes act as anchors for noble metal compounds through a ligand exchange mechanism. The supported samples were then thermally activated and characterized by SIMS, XPS, TEM/EDXS and XRD. Analyses by SIMS showed that the cluster ligand shell was removed during thermal treatment. XPS measurements indicated that the composition of the supported particles corresponded to that of the starting clusters and that the dispersion remained higher in the case of C-PPh2. Well-dispersed bimetallic-supported nanoparticles (1-2 nm) were obtained when cluster 1 was used as the precursor, whereas anchoring of cluster 2 resulted in its fragmentation leading to supported nanoparticles of variable stoichiometries. Reactions with soluble model molecules were carried out to prove the chemical bonding of 1. Crystallization of the new cluster [Ru5PtC-(CO)(14){(PPh2CH2)(2)NC3H7}] confirmed the chemical bonding of cluster 1 onto the C-PPh2 support through a ligand exchange mechanism involving COD.

Heteroleptic triphenylphosphine carbonyl palladium clusters of different nuclearities were prepared under mild conditions by only varying the amount of ligand (PPh3) used in the synthesis: three different clusters were successfully isolated after CO bubbling in a solution of [Pd2(dba)3] (dba=dibenzylideneacetone) with 3, 1 or 0.5equiv of PPh3, which led, respectively, to [Pd4(CO)5(PPh3)4] (1), [Pd10(CO)12(PPh3)6] (2) and [Pdn(CO)x(PPh3)y] (3) (n≈24). The molecular structures of compounds 1 and 2 were determined by X-ray crystallography. The metal cores in these compounds were shown to consist in a butterfly for 1 and a bridged octahedron for 2. Compound 3 was shown to be at the boundary between molecular clusters and colloidal particles with tentative formulation arising from characterization data. These three clusters and the known [Pd10(CO)12(PBu3)6] and [Pd12(CO)15(PBu3)7] were submitted to NaBH4 reduction. The Pd4 cluster 1 did not react. The colloidal Pdn species led to no isolable product. By contrast, the two Pd10 and the Pd12 clusters led to reduction products, isolated as NEt4+ salts. In the case of the reduced Pd12 cluster, its structure was resolved by X-ray crystallography: the metal core consists of a face-capped octahedron. The reduced species reacted readily with Au(PPh3)+, confirming their anionic nature.

Introduction The present work deals with fundamental investigations of molecular approaches aimed at preparing, step-by-step, noble metal-based carbon-supported catalysts from grafted coordination complexes, or organometallic clusters previously anchored on specifically designed organic spacers. Although activated carbons are extensively used as catalyst supports for many liquid phase applications, tailored surface chemistry of these materials definitely remains a challenge when the functionalization is extended beyond the stage of mere oxidation. In this case, a three-step procedure was first developed to obtain a phosphine-functionalized carbon. Carefully selected Pd coordination compounds and organometallic homoor heterometallic clusters containing Pd, Pt and/or Ru were then chemically grafted onto the functionalized support, activated under appropriate conditions according to the various precursors used, and converted into supported nanoparticles that were thoroughly characterized in terms of composition, dispersion and particle size. The successive steps were monitored whenever possible by various advanced physico-chemical techniques.

C129H114AuF6O12P7Pd9, trigonal, R (3) over bar (no. 14 8), a = 22.520(4) angstrom, c = 39.433(7) angstrom, V 17319 angstrom(3), Z = 6, R-gt(F) = 0.047, wR(ref)(F-2) = 0. 129, T = 120 K.

An active carbon support has been functionalized in order to introduce at its surface chelating phosphine groups. This has been done in several steps, which have each been studied in detail and optimized in turn. The first step consisted of increasing the number of oxygenated surface groups by oxidative treatment with HNO3. The second step involved the coupling of an amine with the surface carboxylic groups by formation of an amide bond. Various coupling agents were studied, of which SOCl2 was found to be the most efficient. Fluorinated and brominated amines were used as model amines (easier surface quantification by XPS thanks to the presence of heteroatoms such as F or Br), before reacting ethylenediamine. The pending arm of the diamine could then be further transformed into the desired bidentate phosphine in the last step. The success of the procedure was confirmed, and proof for actual surface chemical reactions was obtained. Two coordination compounds, Pd(dba)(2) and Ru-3(CO)(12), were then incorporated on the starting carbon support and on the functionalized one. It was found that the presence of chelating phosphine groups at the surface of the functionalized support allowed to increase the yield of incorporation and the metallic dispersion at the surface, probably via a ligand exchange mechanism. Nanometer-sized Pd and Ru particles were evidenced by TEM.

In recent years, the synthesis of carbonyl phosphine clusters has received a lot of interest.They can be used as nanoscopic building blocks for a variety of applications including supported catalysts.Once incorporated onto a matrix of interest, the ligands sheath can be removed selectively to yield nanoparticles of controlled size and composition.In particular, we are interested in the synthesis of gold-palladium clusters to produce bimetallic nanoparticle catalysts for applications in selective oxidations.The chosen strategy to reach this goal was to start from palladium clusters, or their reduced form, and to react them with Au + fragments.Here, we wish to report the synthesis of the starting Pd clusters and their reactivity towards reducing agents.In addition, the direct reaction of Pd compounds with [Au(PPh 3 )Cl] was also explored.In a first step, a new cluster, [Pd 10 (CO) 12 (PPh 3 ) 6 ], was prepared by reacting [Pd 2 (dba) 3 ] with one equivalent of PPh 3 under a CO atmosphere.It was fully characterised by NMR, IR and X-ray crystallography.The metal framework of this cluster was shown to consist in a palladium octahedron with four edges bridged by additional palladium atoms.The CO ligands adopt a ( 2 coordination mode on Pd-Pd edges, as expected from the CO stretching frequencies observed in the IR spectrum.By varying the amount of PPh 3 in the synthesis (0,5 to 3 eq.),clusters of different nuclearities were obtained.In a second step, the clusters [Pd 12 (CO) 17 (PBu n 3 ) 5 ],[Pd 10 (CO) 12 (PBu n 3 ) 6 ] and [Pd 10 (CO) 12 (PPh 3 ) 6 ] were reduced using NaBH 4 .For example, when [Pd 12 (CO) 17 (PBu n 3 ) 5 ] was reacted with NaBH 4 , the monoanionic compound (NEt 4 )[Pd 12 H x (CO) 12 (PBu n 3 ) 6 ] (x = 0 or 1) was obtained.The success of the synthesis was established by IR and NMR, and confirmed by X-ray crystallography.The crystal structure comprised the reduced cluster and its counter-ion in a 1:1 ratio.Finally, when reacting different Pd compounds with [Au(PPh 3 )Cl], Pd clusters or positively charged Au complexes were obtained in all cases except one where a mixed-metal cluster was isolated.