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Metal complex catalysis, in which coordination compounds are designed as catalysts for chemical transformations employing noncovalent interactions, is emerging as a powerful catalytic method for organic synthesis. One of the main advantages of metal catalysis is that coordination compounds can promote various organic transformations not only by coordination bond but also through noncovalent interactions, such as hydrogen, halogen, chalcogen, pnictogen, tetrel and triel bonds, as well as metal-metal, cation-π, anion-π, lone pair-π, π-π stacking, agostic, pseudo-agostic, anagostic, dispersion-driven, lipophilic, etc., or their cooperation. In recent years, the concept of designing metal complex catalysts with noncovalent bond donor or acceptor sites has emerged as a promising strategy for developing selective catalytic transformations. In this review we discuss several recent relevant examples on the auxiliary/crucial role of noncovalent interactions in functionalization of alkanes, alkenes, alkynes, aromatics, heterocycles, aldehydes, ketones and alcohols catalyzed by metal complexes.

Functionally substituted cyano carbonyl compounds have been synthesized by reactions of 1-chloro-oxiranecarbaldehyde acetals and α-chlorobenzyl diethoxymethyl ketones with potassium cyanide in DMF.

3-Diethoxymethyl-3-hydroxy-3,9-dihydro-2H-benz[4,5]imidazo[2,1-b]thiazol-4-ium salts were synthesized by reaction of chloro oxiranes or isomeric α-chloro ketones with 2-mercaptobenzimidazole. The acetal group of the aforementioned salts undergoes hydrolysis in acidic medium to liberate aldehyde which would react with the NH-moiety of mercaptobenzimidazole, thus leading to cycle expansion with the formation of 3,3,4-trihydroxy-3,4-dihydro-2H-benz[4,5]imidazo[2,1-b][1,3]thiazinium salts. In DMSO solution, the 3,3,4-trihydroxythiazine moiety of the latter compounds is oxidized into 3,4-dioxothiazine one existing in enol form.

Three known multinuclear Zn(II)-arylhydrazone complexes, [Zn{(CH3)2SO}(H2O)(L1)] (1), [Zn2(CH3OH)2(μ-L2)2] (2) and [Zn4(μ-OH)2(1κO:2κO-HL3)4(κO-HL3)2(H2O)4] (3) were prepared upon reaction of ZnCl2 or Zn(CH3COO)2·2H2O with 3-(2-(2-hydroxy-4-nitrophenyl) hydrazineylidene) pentane-2,4-dione (H2L1), 3-(2-(2-hydroxyphenyl)hydrazineylidene)pentane-2,4-dione (H2L2) and 2-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl)benzoic acid (H2L3), respectively, in methanol solution. Compounds 1–3 were tested as catalysts for the cyanosilylation reaction of a diversity of both aliphatic and aromatic aldehydes with trimethylsilyl cyanide yielding the corresponding cyanohydrin trimethylsilyl ethers in high yields (72–98%) in methanol and at room temperature.

Two known iron(iii) complexes, [Fe(H2O)3(L1)]·xH2O (x = 4 (1), 5 (2)) and [Fe(H2O)3(L2)]·3H2O (3), bearing the basic forms of 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxybenzenesulfonic acid (H3L1) and 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonic acid (H3L2), were prepared and used as homogeneous catalysts for cyanosilylation of a variety of aldehydes with trimethylsilyl cyanide leading to the corresponding cyanohydrin trimethylsilyl ethers. High yield (up to 98 %) was observed in the reaction catalyzed by 3 at room temperature in methanol.