Ji Yeon Ryu

Ruthenium–Cobalt Bimetallic Supramolecular Cages via a Less Symmetric Tetrapyridyl Metalloligand and the Effect of Spacer Units

The self-assembly of C(s)-symmetric tetrapyridyl cobalt-metalloligand 2 with three half-sandwich diruthenium acceptors, 3-5, led to the formation of A4D2 (A = acceptor, D = donor) metallacages 6-8, as shown by ESI mass spectrometry, NMR spectroscopy, and X-ray crystallography. The solid-state structures of 6-8 revealed that the length of the acceptor unit greatly influences the molecular packing of these metallacages. Hence, in the solid state, 6-8 can be considered to have waterwheel-shaped, tweezer-shaped, and butterfly-like architectures, respectively.

Selective Formation of Heterometallic Ru–Ag Supramolecules via Stoichiometric Control of Multiple Different Tectons

Stoichiometric control of Ru, Ag, and tetrazolyl ligands resulted in the formation of different heterometallic Ru-Ag supramolecular architectures. Although the reaction of Ru and 5-(2-hydroxyphenyl)-1H-tetrazolyl (LH2) in a molar ratio of 2:1 or 6:4 resulted in the formation of dimeric or hexameric Ru complexes, Ag metal ions caused the Ru complexes to form three-dimensional cylindrical Ru6Ag6L6 and double-cone-shaped Ru6Ag8L6 complexes by occupying vacant coordination sites.

Self‐Assembly of Novel Thiophene‐Based BODIPY RuII Rectangles: Potential Antiproliferative Agents Selective Against Cancer Cells

Novel Ru (2+2) rectangles were designed and synthesized by self-assembly of a new thiophene-functionalized dipyridyl BODIPY ligand, BDPS, and ruthenium(II) precursors. The complexes exhibited dose-dependent antiproliferative activities against cancer cells, in which some compounds selectively kill cancer cells. The net fluorescence due to BODIPY allowed us to visualize their location inside cancer cells. Moreover, the metalla-rectangles displayed substantial propensity to bind with biomolecules.

Methylaluminoxane-Free Chromium Catalytic System for Ethylene Tetramerization

Ethylene tetramerization catalyst systems comprising a Cr(III) complex containing PNP ligands and methylaluminoxane (MAO) are useful for the production of 1-octene. However, a concern with these systems is the use of expensive MAO in excess. Herein, we report a catalytic system that avoids the use of MAO. Metathesis of CrCl3(THF)3 and [(CH3CN)4Ag]+[B(C6F5)4]− afforded [L4CrIIICl2]+[B(C6F5)4]− (L = CH3CN or tetrahydrofuran (THF)), which was converted to [(PNP)CrCl2L2]+[B(C6F5)4]−, where PNP is iPrN(PPh2)2 (1) or [CH3(CH2)16]2CHN(PPh2)2 (2). The molecular structures of [(THF)4CrIIICl2]+[B(C6F5)4]− and [1-CrCl2(THF)2]+[B(C6F5)4]− were unambiguously determined by X-ray crystallography. The cationic (PNP)CrIII complexes paired with [B(C6F5)4]− anions, that is, [(PNP)CrCl2(CH3CN)2]+[B(C6F5)4]−, exhibited high activity in chlorobenzene when activated with common trialkylaluminum species (Me3Al, Et3Al, and iBu3Al). The activities and selectivity were comparable to those of the original MAO-based Sasol system (1-CrCl3/MAO). When activated with Et3Al or iBu3Al, the Cr complex, [2-CrCl2(CH3CN)2]+[B(C6F5)4]−, which bears long alkyl chains, showed high activity in the more desirable methylcyclohexane solvent (89 kg/g-Cr/h) and much higher activity in cyclohexene (168 kg/g-Cr/h). Other advantages of the [2-CrCl2(CH3CN)2]+[B(C6F5)4]−/Et3Al system in cyclohexene were negligible catalyst deactivation, formation of only a negligible amount of polyethylene side product (0.3%), and formation of fewer unwanted side products above C10. The [B(C6F5)4]− anion is compatible with trialkylaluminum species once it is not paired with a trityl cation. Hence, [(PNP)CrCl2(CH3CN)2]+[B(C6F5)4]−/Et3Al exhibited a significantly higher activity than that of a previously reported system composed of [Ph3C]+[B(C6F5)4]−, that is, 1/CrCl3(THF)3/[Ph3C]+[B(C6F5)4]−/Et3Al.

Ruthenium-Catalyzed C–H Activation of Salicylaldehyde and Decarboxylative Coupling of Alkynoic Acids for the Selective Synthesis of Homoisoflavonoids and Flavones

Homoisoflavonoids were formed in DMSO exclusively, and flavones were formed in t-AmOH when salicylaldehyde and alkynoic acids reacted with [Ru(p-cymene)Cl2]2 and CsOAc. They were formed through C-H activation of salicylaldehyde and decarboxylative coupling of alkynoic acid. This reaction system showed good yields, broad substrate scope, and good functional group tolerance. It was found that chalcone was an intermediate in the formation of both homoisoflavonoid and flavone.

Unique Ruthenium Bimetallic Supramolecular Cages From C4-Symmetric Tetrapyridyl Metalloligands

The self-assembly of C4-symmetric tetrapyridyl metalloligands containing Fe or Co and diruthenium electron acceptors by means of dative coordination bonding led to the formation of six different heterobimetallic supramolecules. All complexes were characterized by X-ray crystallography, ESI mass spectrometry, and 1H NMR (in the case of diamagnetic systems) spectroscopy. The bridging units in the diruthenium complexes greatly influenced the geometrical preference of the supramolecular structures, resulting in the formation of different architectures, namely A4D2 or A6D3 (A = acceptor, D = donor). Depending on the bridging unit, A4D2 tetragonal prism, A4D2 molecular tweezer, or A6D3 triple-decker complexes were obtained selectively. The self-assembly of an unexpected triple-decker type Ru12Fe3 heterobimetallic species was also observed.

Facile synthesis of a dimeric titanium(IV) complex with terminal TiO moieties and its application as a catalyst for the cycloaddition reaction of CO2 to epoxides

In this report, facile and exclusive synthesis of dimeric titanium(IV) complex with a terminal TiO moiety from the reaction between novel pyridine-based tridentate ligand (LH2) and Ti(O-i-Pr)4 under the bubbling of wet air is presented. Alternatively, the same dimeric Ti complex was obtained via wet air bubbling of monomeric LTi(O-i-Pr)2 or addition of the same equiv. of H2O into LTi(O-i-Pr)2. All compounds including LH2 and two titanium complexes were characterized by single crystal X-ray analyses. Newly synthesized terminal oxo-titanium compound is the first example of structurally characterized dimeric terminal oxo-titanium compound having no TiO→Ti bonds. Two titanium complexes were used as effective catalysts for the cycloaddition of CO2 to propylene oxide in the presence of various kinds of cocatalysts such as n-Bu4PBr, n-Bu4NI, n-Bu4NBr, n-Bu4NCl, PPNCl, and DMAP.

Bifunctional N-heterocyclic carbene ligands for Cu-catalyzed direct C–H carboxylation with CO2

Diethylene glycol-functionalized imidazo[1,5-a]pyridin-3-ylidenes (DEG-ImPy) have been developed as bifunctional N-heterocyclic carbene ligands. The DEG-ImPy Cu(I) complexes efficiently catalyzed the direct C–H carboxylation of benzoxazole with CO2, showing higher isolated yields than those with the N,N′-(2,6-diisopropylphenyl)imidazolylidene Cu catalyst.

Crystal structure of 1-(5-amino-2H-tetra-zol-2-yl)-2-methyl-propan-2-ol.

The title compound, C5H11N5O, crystallized with two independent molecules in the asymmetric unit. The two molecules differ in the orientation of the 2-methylpropan-2-ol unit, with the hydroxy H atoms pointing in opposite directions. In the crystal, molecules are linked via O—H⋯O and N—H⋯O hydrogen bonds, forming ribbons propagating along [10-1]. The ribbons are linked via N—H⋯N hydrogen bonds, forming a three-dimensional structure.

A Regulation of Regiodivergent Routes for Enantioselective Aldol Addition of 2-Alkyl Allenoates with Aldehydes: α-Addition versus γ-Addition

A method for the regioselective asymmetric aldol addition of 2-alkyl allenoates with aldehydes to provide an α- or γ-adduct depending on the aldehyde pair is reported. In most cases, except enals, a mixture of a chiral bromoborane with 2-alkyl allenoates in the presence of iPr2NEt can react with aldehydes to provide efficient γ-addition products as single isomers containing axial and central chirality. On the other hand, observations indicate that enals undergo α-addition to yield highly functionalized adducts, including an α-carbon quaternary center in high levels of diastereo- and enantioselectivity.