Conventional methods for preparing catalysts for the immobilization of N-heterocyclic carbenes (NHC)-metal complex use the substituent on the nitrogen as the immobilization site with the support, and the bulkiness of the substituent on the nitrogen, which is a characteristic of NHC ligands, cannot be fully utilized. In this study, we focused on the backbone carbon of NHC and devised a new catalyst design that uses backbone carbon as the binding point with the support. First, various silyl groups were introduced into the backbone carbon of IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), and Si–IPr–Pd complex catalysts were synthesized. The electronic properties of the introduced silyl groups were investigated, and it was confirmed that the introduction of electron-donating silyl groups enhanced the catalytic activity in C–N coupling reaction. Next, we applied this knowledge to the immobilization of Si–IPr–Pd complex catalyst with a dimethylchlorosilyl group on polystyrene resin to develop a new immobilized NHC–Pd complex catalyst with an electron-donating oxosilyl group as the binding point to the support. Finally, the catalytic performance was evaluated in the C–N coupling reaction, and the catalyst exhibited high activity, and the amount of residual Pd in the filtrate after the reaction was below the detection limit (<1 ppm).

Highly selective C–C bond formation via the cleavage of inactive C–H bonds is an attractive method for constructing complex carbon skeletons such as natural products and pharmaceuticals. On the other hand, heterogeneous catalysts, and in particular supported metal catalysts, have attracted considerable attention since they can reduce environmental loads thanks to their high recyclability. This review paper describes how ruthenium catalysts supported on CeO₂ or ZrO₂ (Ru/CeO₂ or Ru/ZrO₂) can act as heterogeneous catalysts for various C–C bond-forming reactions via cleavage of an inactive C–H bond. These catalysts exhibit excellent environmentally-friendly performance, such as high recyclability and almost no metal contamination of the products. Furthermore, this paper presents new methods for synthesizing heterocyclic compounds via the direct transformation of inactive aromatic C–H bonds under ruthenium catalysis. Ru complex catalysts promoted the cycloaddition of C(sp²)–H bonds of aromatic carboxylic acids and aromatic amides to alkynes, aldehydes, ketones, and imines, which consequently enabled a one-step construction of heterocyclic compounds such as isobenzofuranone and isoindolinone.

Heavy oil cracking in most Japanese refineries adopts the residue fluid catalytic cracking (RFCC) process. The sulfur content of low sulfur fuel oil (LSFO) must be reduced to below 0.5 wt% to comply with new International Maritime Organization (IMO) regulations. To achieve this, the residue hydrodesulfurization (RDS) unit must be operated under more severe conditions. In this study, an RDS catalyst system to treat deasphalted oil (DAO) from the solvent deasphalting (SDA) unit was developed. This system allows co-production of both RFCC feedstocks and LSFO from the vacuum residue (VR) fraction simultaneously and flexible refinery operation. VR has much amount of vanadium and nickel. The SDA process selectively reduces large molecules containing vanadium and nickel, both catalyst poisoning materials. Such metal compounds in DAO are easy to remove, but due to their reactivity, the catalysts deactivate faster than conventional atmospheric residue (AR). Therefore, we developed a new RDS catalyst system for DAO treatment. This new system can suppress metal deactivation in the RDS unit and reduces the amount of nitrogen in the products, which in turn leads to increased RFCC conversion.

A novel ruthenium carbene complex [Cl₂(Cy₃P)(4-Me₃Si-IPr)Ru=CHPh] 1, in which the IPr [1,3-bis(2,6-diisopropylphenyl)-2H-imidazol-2-ylidene] ligand is modified via the introduction of the electropositive Me₃Si-group at the 4-position of the N-heterocyclic carbene (NHC) backbone, was synthesized and spectroscopically charac-terized. This type of second-generation Grubbs pre-catalyst 1 showed excellent catalytic activity for the ring-closing metathesis of diethyldiallylmalonate, with notably better activity compared to the commercially available first-generation Grubbs pre-catalyst [Cl₂(Cy₃P)₂Ru=CHPh] and comparable activity to the second-generation Grubbs pre-catalyst [Cl₂(Cy₃P)(IPr)Ru=CHPh].

A series of Pt-base bimetallic catalysts supported on CeO₂ (Pt₃M/CeO₂, M = Bi, Ga, Ge, In, Sn) were prepared and tested in methane coupling under an electric field at 300 °C. Modification of Pt by Sn or Bi greatly enhanced the yield of higher hydrocarbons, in which two orders of magnitude higher yield was obtained. Pt₃Bi showed not only much higher catalytic activity than Pt₃Sn when normalized by electric power, but also higher olefin content.