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Paramagnetic titanocene complexes containing the unsaturated carbyl group which consists of one and half molecule of 1,4-bis(trimethylsilyl)buta-1,3-diyne (BSD) are formed by the reduction of titanocene dichlorides with one molar equivalent of magnesium in the presence of 1.5 molar equivalent BSD in tetrahydrofuran (THF) for titanocene moieties Ti(η5-C5H5 − nMen)2 (n = 5 (1), 4 (2), and 3 (3)) and Ti{Me2Si(η5-C5Me4)2} (4). The non-methylated titanocene moiety affords under identical conditions known diamagnetic bis(η5-cyclopentadienyl)-2,4-bis(trimethylsilylethynyl)-3,5-bis(trimethylsilyl)titanacyclopenta-2,4-diene (5) as the major product. Crystal structures of 3 and 4 show the same bonding scheme for the 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl ligand as previously found for compound 1 [P.-M. Pellny, F.G. Kirchbauer, V.V. Burlakov, A. Spannenberg, K. Mach, U. Rosenthal, Chem. Commun. (1999) 2505]. Compound 1 is stable against weak proton donors like methanol or alk-1-ynes even at 90 °C, however, it undergoes retroreaction when oxidized by PbCl2 in THF, yielding nearly quantitatively BSD and [TiCl2(η5-C5Me5)2].

Ru 3 (CO) 9 (PPh 3 ) 3 and Ru 3 (CO) 9 (PPh 2 CH 2 CH 2 Si(OMe) 3 ) 3 have been heterogenized in silica matrices by the sol–gel method. Gels prepared with Ru 3 (CO) 9 (PPh 2 CH 2 CH 2 Si(OMe) 3 ) 3 were tested in the hydrogenation and isomerization of 1-hexene. At H 2 -pressures of 16 psi in repeated runs (15 h, 90 °C) turnover numbers for 1-hexene hydrogenation were between 380 and 460. Isomerization products were trans -2-hexene, cis -2-hexene and trans -3-hexene. No cis -3-hexene, 2-methyl-1-pentene and 2-methylpentane were found. Leaching of ruthenium in each run was around 0.05% of ruthenium present in the original gel. UV–VIS and FT-IR spectra of the pure cluster compounds and the gels before and after the catalytic reactions showed that during the gel preparation some Ru 3 units remain intact, but are cleaved when the gel is heated under vacuum or used in catalytic hydrogenation reactions.

MoO2(acac)2 has been encapsulated in silica matrixes prepared by hydrolysis/condensation of tetraethylorthosilicate. Alternatively, hybrid organic–inorganic matrixes were prepared by adding 3-(triethoxysilyl)propylethylenediamine or 1,4-bis(triethoxysilyl)benzene to the reaction mixture. All systems were tested in the epoxidation of cyclohexene or cis-cyclooctene at

Addition of poly(ethylene oxide) (PEO) to the catalytic system MoO2(acac)2/TBHP/t-butanol used for epoxidation of olefins allowed an easy strategy for catalyst recycling and product recovery. This procedure is based upon catalyst removal by precipitation of a complex with the polymer, being advantageous over other similar recycling methodologies in that there is no requirement for specially prepared catalysts or solvents. Although some catalyst leaching is detected, the epoxidation of cis-cyclooctene was achieved with global turnover numbers close to 650. © 2002 Elsevier Science B.V. All rights reserved.

Both Ru3(CO)12 and Ru3(CO)9(PPh3)3 were tested in their ability to hydrogenate and isomerize 1-hexene at 30, 60 and 90°C in the presence and absence of H2. The effect of excess PPh3 was studied and interpreted by the different capacity of the cluster to replace CO by PPh3 against CO. Some reactions under irradiation with visible light were also performed. The cluster mixtures obtained in hydrogenation reactions were characterized by IR spectroscopy and shown to contain H4Ru4(CO)12 and H4Ru4(CO)12−n(PPh3)n (n=1–4). Main isomerization products were trans-2-hexene (up to 61%), cis-2-hexene (up to 23%) and trans-3-hexene (up to 20%). At H2-pressures of 32 and 48 psi, Ru3(CO)12 was more active in hydrogenation, at 16 psi Ru3(CO)9(PPh3)3 was the better hydrogenation catalyst. 2-Methyl-1-pentene (up to 4%) and 2-methylpentane (up to 0.55%) were identified as by-products.

CH 3 ReO 3 has been heterogenized inside the porous system of hybrid silica matrixes via the sol–gel method using 1,4- bis (triethoxysilyl)benzene as a co-condensation agent and 4-((3-triethoxysilyl)propylamino)pyridine hydrochloride as a hydrolysable ligand. The resulting solids are stable and recyclable epoxidation catalysts.