Highly active and selective: A supported Ru5PtSn nanoparticle cluster (the picture shows an axial projection of a tomogram), prepared from the carbonyl cluster [PtRu5(CO)15(μ‐SnPh2)(μ6‐C)], is an excellent catalyst in the single‐step hydrogenation of dimethyl terephthalate to cyclohexanedimethanol under mild conditions (100 °C, 20 bar H2).

The six-membered heavy atom heterocycles [Re(2)(CO)(8)(μ-SbPh(2))(μ-H)](2), 5, and Pd[Re(2)(CO)(8)(μ-SbPh(2))(μ-H)](2), 7, have been prepared by the palladium-catalyzed ring-opening cyclo-dimerization of the three-membered heterocycle Re(2)(CO)(8)(μ-SbPh(2))(μ-H), 3. The palladium atom that lies in the center of the heterocycle 7 was removed to yield 5. The palladium removal was found to be partially reversible leading to an unusual example of host-guest behavior. A related dipalladium complex Pd(2)Re(4)(CO)(16)(μ(4)-SbPh)(μ(3)-SbPh(2))(μ-Ph)(μ-H)(2), 6, was also formed in these reactions of palladium with 3.

Cationic methyl Pd() complexes are described in which the new heterofunctional phosphine ligands Ph 2 PNHC(O)Me 1 or Ph 2 PN(Me)C(O)Me 3 behave as rigid and/or hemilabile P,O chelates. The chelating ability of 3 is higher than that of 1 and both are compared to that of other P,O ligands, such as the keto-and amido-phosphines Ph 2 PCH 2 C(O)Ph and Ph 2 PCH 2 C(O)NPh 2 , respectively. The crystal structure of 1 reveals the presence in the solid-state of an intermolecular hydrogen-bonded network N-H ؒ ؒ ؒ O and that of12b establishes the presence of both a chelating and a monodentate ligand 1 in the same complex. Carbonylation of the cationic methyl complexes 8a, 17, 18a and 20a afforded the corresponding acetyl complexes in which this ligand occupies a position cis to phosphorus, irrespective of that of the alkyl ligand in the precursor complex.

The catalytic performance of cluster-derived PtFe/SiO(2) bimetallic catalysts for the oxidation of CO has been examined in the absence and presence of H(2) (PROX) and compared to that of Pt/SiO(2). PtFe(2)/SiO(2) and Pt(5)Fe(2)/SiO(2) samples were prepared from PtFe(2)(COD)(CO)(8) and Pt(5)Fe(2)(COD)(2)(CO)(12) organometallic cluster precursors, respectively. FTIR data indicate that both clusters can be deposited intact on the SiO(2) support. The clusters remained weakly bonded to the SiO(2) surface and could be extracted with CH(2)Cl(2) without any significant changes in their structure. Subsequent heating in H(2) led to complete decarbonylation of the supported clusters at approximately 350 degrees C and the formation of Pt-Fe nanoparticles with sizes in the 1-2 nm range, as indicated by HRTEM imaging. A few larger nanoparticles enriched in Pt were also observed, indicating that a small fraction of the deposited clusters were segregated to the individual components following the hydrogen treatment. A higher degree of metal dispersion and more homogeneous mixing of the two metals were observed during HRTEM/XEDS analysis with the cluster-derived samples, as compared to a PtFe/SiO(2) catalyst prepared through a conventional impregnation route. Furthermore, the cluster-derived PtFe(2)/SiO(2) and Pt(5)Fe(2)/SiO(2) samples were more active than Pt/SiO(2) and the conventionally prepared PtFe/SiO(2) sample for the oxidation of CO in air. However, substantial deactivation was also observed, indicating that the properties of the Pt-Fe bimetallic sites in the cluster-derived samples were altered by exposure to the reactants. The Pt(5)Fe(2)/SiO(2) sample was also more active than Pt/SiO(2) for PROX with a selectivity of approximately 92% at 50 degrees C. In this case, the deactivation with time on stream was substantially slower, indicating that the highly reducing environment under the PROX conditions helps maintain the properties of the active Pt-Fe bimetallic sites.

Cyclododecene (CD) is an important intermediate in the chemical industry since it figures eminently in the synthesis of dicarboxylic aliphatic acids, ketones, cyclic alcohols, lactones and other useful materials, including 12-laurolactam and dodecanedioic acid which are monomers used in the manufacture of nylon 12, nylon 612, copolyamides and polyesters all of which have extensive applications.Two of us previously reported [1] that cyclododecene may be efficiently produced in a low-temperature, solvent-free fashion by selectively hydrogenating 1,5,9-cyclododecatriene (CDT) in the presence of a Ru 6 Sn nanoparticle catalyst. The actual catalyst was derived [2] from the precursor carbonylate [Ru 6 C(CO) 16 SnCl 3 ]À , in which the chlorinated tin atom bridges two of the six ruthenium atoms of the octahedral cluster.[3] From in situ extended X-ray absorption fine structure (EXAFS) and FTIR studies [1] on the denuded active Ru 6 Sn nanoparticle catalyst it was clear a residual chlorine atom remained attached to the active catalytic entity (see Conscious of the known modifying effect of Sn on Ru (and other) catalysts, [1,4] and also of the difficulties, such as reproducibility, frequently associated with the presence of chlorine in supported catalysts, [5] we have set about to prepare a range of new Ru-Sn carbonyl complexes for use as catalyst precursors that are free of Cl (and also of the carbidic carbon), present in the previously reported active catalyst. [3] In evolving a suitable method of preparation, we have arrived at a means of systematically altering the Ru:Sn ratios in bimetallic nanoparticles, consisting of clusters with a total atom content of as little as two and as large as ten atoms.Herein we describe the synthesis and structures of four new tin-containing tetraruthenium cluster complexes, two of which we have tested in their denuded form and have found to be active catalysts for the highly selective hydrogenation of CDT to CD. Each compound contains an approximately square-planar cluster of four ruthenium atoms with two quadruply bridging SnPh ligands, one on each side of the Ru 4 square (Scheme 1). The molecular structures of 1 and 4 are shown in Figures 1 and 2, respectively. Compound 1 contains twelve carbonyl ligands like its parent compound, whereas in compounds 2-4, two, three, and four of the CO ligands were replaced by SnPh 2 groups that bridge the Ru-Ru edges of the Ru 4 square. The m 4 -SnPh stannylyne ligands present in these clusters are very rare. In fact, there is only one reported example of a m 4 -SnPh ligand; this was observed for the compound [Ru 5 (CO) 11 (h 6 -C 6 H 6 )(m 4 -SnPh)(m 3 -CPh)]. [6] Compounds 1, 2, and 4 were chosen for our catalytic investigations. The compounds were deposited (ca. 2 % metal loading) on Davison 923 silica mesopore (38 ) and were activated by heating to 200 8C for 2 h in vacuum. Catalytic tests were carried out as described in the Experimental Section. A typical kinetic plot for the hydrogenation of CDT at 393 K by the Ru 4 Sn 6 catalyst supported ...

New hexameric cyclophenyleneethynylenes (CPEs, 1) were synthesized by alkyne metathesis of meta‐dipropynylated benzenes. Treatment of one of these CPE derivatives (R1=tert‐butyl, hexyl, dodecyl; R2=H, methyl) with [Os3(CO)10(MeCN)2] led to a decacarbonyltriosmium–CPE complex in which the planarity of the ring was significantly disrupted, as evidenced by the results of the single‐crystal X‐ray diffraction analysis.

Minute stoichiometric bimetallic clusters rich in tin (PtSn 2, RhSn 2, and RuSn 2) are powerful selective hydrogenation catalysts: these "molecular metallic" entities, supported on mesoporous silica and characterized by aberration-corrected electron microscopy, yield high percentages of cyclododecene (CDE) at fractional conversions ranging from 0.45 to 0.70 of the parent cyclododecatriene (CDT) at modest temperatures and under solvent-free conditions.

New highly dispersed bimetallic nanoscale catalysts based on rhenium combined with antimony or bismuth have been shown to be highly effective for the ammoxidation of 3-picoline to nicotinonitrile (precursor for vitamin B3) under mild conditions in the liquid phase.