An ew catalytic system for the N-monoalkylation of aqueous ammonia with av ariety of alcohols was developed. Water-soluble dicationic complexes of iridium bearingN -heterocyclic carbene andd iammine ligands exhibited high catalytic activity for this type of reaction on the basis of hydrogen-transferp rocesses without generating harmfulo rw asteful byproducts. Various primary amines were efficiently synthesized by using safe, inexpensive, and easily handled aqueous ammonia as an itrogen source.F or example, the reaction of 1-(4-methylphenyl)ethanol with aqueous ammonia in the presence of aw ater-soluble Nheterocyclic carbene complexo fi ridium at 150 8Cf or 40 h gave 1-(4-methylphenyl)ethylamine in 83 %yield.Scheme1.Selective catalytic synthesis of primarya mines by N-alkylation of ammonia with alcohols.[a] Prof.

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Over the past few decades, a number of homogeneous transition metal complex catalysts for efficient organic transformations have been developed. Some of these highly active catalysts have been designed based on the concept of "cooperativity between a transition metal atom and a custom-designed ligand molecule". In this paper, we report the synthesis of a periodic mesoporous organosilica (PMO) catalyst support (BPyOH-BP-PMO) that enables cooperativity between a transition-metal atom and the custom-designed ligand. We immobilized iridium complexes on BPyOH-BP-PMO to produce a heterogeneous catalyst that exhibits excellent catalytic activity for the dehydrogenative oxidation of a variety of alcohols and is superior to a similar previously used homogeneous catalyst. Furthermore, the immobilized catalyst (Ir@BPyOH-BP-PMO) can be recovered by simple filtration and reused without decrease of its catalytic activity. We believe that the concept for the design of the present heterogeneous catalyst would provide important guidance for the development of innovative catalysts.

A series of hexamethylbenzene (HMB)-Ru complexes 2-5 bearing a 4,4'-functionalized 2,2'-bipyridine-6,6'-dionate (bpyO) ligand, which exhibits metal-ligand cooperative catalysis, was prepared with the aim of developing excellent catalyst for dehydrogenative oxidation of alcohols. Interestingly, the catalytic activity increased in the order 3 (CF 3 ) < 4 (OMe) < 2 (H) < 5 (NMe 2 ), where substituents at 4,4'-positions of bpyO ligand are in parentheses. This is different from the order of simple electron-donating ability. DFT calculations revealed that the rate-limiting step is the concerted proton/hydride transfer from the alcohol to the complex. The activation energy decreases as the interaction between the alcoholic proton and the O atom of the bpyO ligand becomes stronger; hence, the introduction of the NMe 2 group decreases the activation energy, whereas that of the CF 3 group increases it. The unexpectedly lower catalytic ability of 4 than that of 2 results from the enthalpy-entropy compensation effect.