In the presence of KOBut, N-heterocyclic carbene-supported half-sandwich complex [Cp­(IPr)­Ru­(pyr)2]­[PF6] (3) (IPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene) catalyzes transfer hydrogenation (TH) of nitriles, activated N-heterocycles, olefins, and conjugated olefins in isopropanol at the catalyst loading of 0.5%. The TH of nitriles leads to imines, produced as a result of coupling of the initially formed amines with acetone (produced from isopropanol), and showed good chemoselectivity. Reduction of N-heterocycles occurs for activated polycyclic substrates (e.g., quinoline) and takes place exclusively in the heterocycle. The TH also works well for linear and cyclic olefins but fails for trisubstituted substrates. However, the CC bond of α,β-unsaturated esters, amides, and acids is easily reduced even for trisubstituted species, such as isovaleriates. Mechanistic studies suggest that the active species in these catalytic reactions is the trihydride Cp­(IPr)­RuH3 (5), which can catalyze these reactions in the absence of any base. Kinetic studies are consistent with a classical inner sphere hydride-based mechanism of TH.

Bismuth molybdate catalysts have been used for partial oxidation and ammoxidation of light hydrocarbons since the 1950s. In particular, there is the synergy effect (the enhancement of the catalytic activity in the catalysts mixed from different components) in different phases of bismuth molybdate catalysts which has been observed and studied since the 1980s; however, despite it being interpreted differently by different research groups, there is still no decisive conclusion on the origin of the synergy effect that has been obtained. The starting idea of this work is to find an answer for the question: does the electrical conductivity influence the catalytic activity (which has been previously proposed by some authors). In this work, highly conductive materials (SnO 2 , ZrO 2 ) and nonconductive materials (MgO) are added to beta bismuth molybdates (β-Bi 2 Mo 2 O 9 ) using mechanical mixing, impregnation, and sol−gel methods. The mixtures were characterized by XRD, BET, XPS, and EDX techniques to determine the phase composition and surface properties. The conductivities of these samples were recorded at the catalytic reaction temperature (300−450 °C). Comparison of the catalytic activities of these mixtures showed that the addition of 10% mol SnO 2 to beta bismuth molybdate resulted in the highest activity while the addition of nonconductive MgO could not increase the catalytic activity. This shows that there may be a connection between conductivity and catalytic activity in the mixtures of bismuth molybdate catalysts and other metal oxides.

Reaction of complex [CpRu(pyr)3][PF6] (3) with the NHC carbene IPr (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) results in the NHC complex [Cp(IPr)Ru(pyr)2][PF6] (4), which was studied by NMR specroscopy and X-ray diffraction analysis. Reaction of [Cp(IPr)Ru(pyr)2][PF6] (4) with LiAlH4 leads to the trihydride Cp(IPr)RuH3 (5) characterised by spectroscopic methods. Heating compound 5 with hydrosilanes gives the dihydrido silyl derivatives Cp(IPr)RuH2(SiR3) (6). Systematic X-ray diffraction studies suggest that complexes 6 have stronger interligand Si∙∙∙H interactions than the isolobal phosphine complexes Cp(Pr3P)RuH2(SiR3).

The NHC (NHC = N-heterocyclic carbene) complex Cp*­(IPr)­RuH3 catalyzes hydrodefluorination of aromatic fluorides at 70 °C with isopropyl alcohol as the reducing reagent. The reaction is selective for aromatic fluorides, as almost negligible C­(sp3)–F bond reduction takes place. The activity decreases from more to less fluorinated substrates, but polyaromatic monofluorides, such as 1-fluoronaphthalene and 6-fluoro-2-methylquinoline, can also be reduced in moderate to good yields. Kinetic studies are consistent with a mechanism based on elimination of NHC and reversible substrate coordination, followed by coordination of the alcohol.

Reactions of carbene complex [Cp(IPr)Ru(pyr) 2 ][BF 4 ] (6, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with excess acetonitrile and LiCl in THF afford complexes [Cp(IPr)Ru-(NCCH 3 ) 2 ][PF 6 ] (7) and Cp(IPr)RuCl (8), respectively. Complex 8 was characterized by NMR and X-ray diffraction analysis. Addition of hydrosilanes to 8 results in silane σ-complexes Cp(IPr)Ru(η 2 -HSiR 3 ) Cl (4), which were characterized by NMR and X-ray studies of Cp(IPr)Ru(η 2 -HSiMeCl 2 )Cl (4b) and Cp(IPr)Ru(η 2 -H 3 SiPh)Cl (4d). The hydrogen−silicon coupling constants of complexes 4 show an unusual trend in that the J(H−Si) values increase from the less-chlorinated complex Cp(IPr)Ru(η 2 -HSiMe 2 Cl)Cl (4c) to the trichloro derivative Cp(IPr)Ru(η 2 -HSiCl 3 )Cl (4a). Reaction of Cp(IPr)RuCl (8) with two equivalents of HSiCl 3 gave the ruthenate complex [IPrH] + [CpRuCl(H) (SiCl 3 ) 2 ] − , characterized by NMR and X-ray study. Addition of hydrosilanes to the cationic complex [Cp(IPr)Ru(NCCH 3 ) 2 ][BAr F 4 ] (9) furnished very unstable cationic silane σ-complexes [Cp(IPr)Ru(η 2 -HSiR 3 )(NCCH 3 )] + ( 5), characterized by low-temperature NMR. Reaction of complex 9 with two equivalents of HSiCl 3 gives the neutral bis(silyl) complex CpRu(NCCH 3 )(H)(SiCl 3 ) 2 and [IPrH] [BAr F 4 ]. Catalytic studies showed that 9 is a poorer catalyst for hydrosilylation of benzaldehyde, benzonitrile, and pyridine than its phosphine analogue [Cp( i Pr 3 P)Ru(NCCH 3 ) 2 ][BAr F 4 ]. The reason for this reduced activity was assigned to the easy dissociation of carbene from the former catalyst.

NHC-supported trihydrides Cp(NHC)RuH3 show excellent catalytic activity in the H/D exchange of pyridine and some other N-heterocycles under mild conditions and low catalyst loading.

A series of half‐sandwich phosphine‐ and NHC‐supported complexes were screened in catalytic transfer hydrogenation of nitriles, N‐heterocycles, olefins, and carbonyls by using ammonium formate as the reductant. Complex [Cp(iPr3P)Ru(NCCH3)2][PF6] (3) was found to be the most efficient catalyst. Mechanistic studies suggested that the formate complexes Cp(iPr3P)Ru(κ2‐O2CH) and Cp(iPr3P)Ru(κ1‐O2CH)(NCCH3) could be the true catalysts in these reactions. An inner‐sphere monohydride mechanism was suggested. Excess free phosphine impedes the catalysis by forming the catalytically inactive bis(phosphine) complex Cp(iPr3P)2RuH.

Different bismuth molybdate catalysts for the selective oxidation of propylene to acrolein were prepared by the sol–gel method, starting from bismuth nitrate, ammonium molybdate, and citric acid. The influence of pH value and theoretical molar Bi/Mo atomic ratio on the complexation and gelation is surveyed using IR spectroscopy, X‐ray diffraction, and BET. Their catalytic activities for the conversion propylene to acrolein are examined.