Jong Hwa Jeong

Relationships among structure and spectroscopic properties in tetrahedrally distorted copper(II) (−)-sparteine dichloride

Abstract The 1:1 mixed crystalline Cu(C15H26N2)Cl2·Zn(C15H26N2)Cl2, 2, and the host lattice material, Zn(C15H26N2)Cl2, 3, were newly prepared and characterized, and the X-ray crystallographic structures of 2 and 3 determined. Further distortion around the Cu(II) center of Cu(C15H26N2)Cl2, 1, was achieved by introducing 1 into the corresponding diamagnetic Zn(II) host lattice. In the 1:1 mixed crystalline, the dihedral angle between the CuN2 and the CuCl2 planes in the Cu(C15H26N2)Cl2 units increased by ∼11° more than that in the neat 1. The ESR and the optical spectral data in solution and solid states were collected for 1 and 2, and the results correlated with the degree of the distortion around the Cu(II) center. The A∥ values of the ESR spectra and the ligand-field transitions are quite sensitive toward the small change in the dihedral angle between the CuCl2 and the CuN2 planes of the Cu(C15H26N2)Cl2 unit.

Synthesis and characterization of a Zn(II) complex of a pyrazole-based ligand bearing a chiral l-alaninemethylester

Abstract Reaction of ZnCl2 with a new ligand N,N-bis(3,5-dimethylpyrazolylmethyl)- l -alaninemethylester (bdmpame) in methanol gives [ZnCl2(bdmpame)]. The structure of [ZnCl2(bdmpame)]·CH2Cl2 has been resolved by X-ray crystallographic analysis. The Zn atom has a distorted tetrahedral geometry involving a nitrogen atom from each pyrazole in bdmpame and two chloro ligands with bond lengths in the range 2.037(4)–2.237(2) A. The nitrogen atom of the l -alaninemethylester group in the compound was not coordinated to the metal center, giving an eight-membered ring in which the nitrogen atoms of each pyrazole in bdmpame are coordinated to the metal center. The results of the catalytic enantioselective reduction of acetophenone promoted by ligand/Zn(OTf)2=1:1 mole ratio in the presence of catecholborane for 48 h at 0°C gives (S)-(−)-1-phenylethanol in 21% ee with 68% yield.

Asymmetric addition of diethylzinc to aromatic aldehydes by chiral ferrocene-based catalysts

Abstract A series of chiral C1- and C2-symmetric ferrocenyl Schiff bases (1a–c), ferrocenyl aminoalcohols (2a), ferrocenylphosphinamides (2b–c), 1,1′-ferrocenyl-diol (3), and 1,1′-ferrocenyl-disulfonamide (4) were prepared and employed as base catalysts or as ligand for titanium(IV) complexes in the asymmetric addition of diethylzinc to aromatic aldehydes. High enantioselectivity up to almost 100% ee was achieved for the alkylation of benzaldehyde and p-methoxybenzaldehyde with 1 or 3. In contrast, however, the β-aminoalcohol (2a) and phosphinamides (2b and c) that are ubiquitous classes of base catalysts for this reaction proved inefficient in our hands, regardless of the types of substrates or reaction conditions. Comparative studies show that there exist various reaction parameters governing not only chemical yields but also optical yields. These include steric and electronic environment of the substrate, the solvent, the reaction temperature, and the nature of the ferrocene moieties.

Synthesis and properties of a tetraaza macrocyclic ligand containing 2-pyridylmethyl pendant arms and its copper(II) and nickel(II) complexes: crystal structure of the copper(II) complex

Abstract A new functionalized macrocyclic ligand 2,13-bis(2′-pyridylmethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.118O712]docosane (L2) containing two 2-pyridylmethyl pendant arms has been prepared by the one-step reaction of 3,4-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.118O712]docosane (L1) with 2-(chloromethyl) pyridine. The octahedral complexes [NiL2](ClO4)2 and [CuL2](ClO4)2, in which two pyridyl groups are coordinated to the metal ion, have been prepared and characterized. The crystal structure of [CuL2](ClO4)2 shows that the complex is centrosymmetric and the metal center has a tetragonally distorted octahedral geometry. In concentrated HClO4 solutions, the coordinated pyridyl groups of [CuL2]2 are protonated and are removed from the coordination sphere. However, those of [NiL2]2 are not protonated but are coordinated to the metal ion even in 3.0 M HClO4. The macrocycle L2 reacts more slowly with copper(II) ion than does L1.

Template synthesis of N-aminoethylated hexaaza macrobicyclic nickel(II) complexes containing one four-membered chelate ring

Abstract New nickel(II) complexes of the hexadentate macrobicycles 6-(2-aminoethyl)-1,3,6,9,11,14-hexaazabicyclo[12.3.1]octadecane (1), 6-(2-aminoethyl)-1,3,6,9,11,14-hexaazabicyclo[12.2.1]heptadecane (2), and 6-(2-aminoethyl)-1,3,6,9,11,15-hexaazabicyclo[13.3.1]nonadecane (3) have been prepared selectively by the metal template condensation of formaldehyde with tris(2-aminoethyl)amine and a triamine (1,4,8-triazaoctane, 1,4,7-triazaheptane, or 1,5,9-triazanonane). The complexes [Ni(L)]2+ (L=1, 2, or 3), in which one 2-aminoethyl pendant arm is coordinated to the metal ion, have distorted octahedral coordination geometry with a rarely observed four-membered chelate ring. They are extremely stable in neutral or basic aqueous solutions but are readily decomposed in acidic conditions. The decomposition rate of the complexes in HClO4 solutions is not affected significantly by the ring size of the macrobicyclic ligands. Synthesis and characterization of the nickel(II) complexes are reported, together with the crystal structure of [Ni(1)][ZnCl4].

Synthesis and crystal structure of bis[(μ-κO:κO′-acetato)(μ-κO:κ2O′-acetato)][(η5-Cp)tris(dimethylphosphito-P)cobalt-O,O′,O″]yttrium(III)

Abstract The [η5-CpCo{P(O)(OMe)2}3Y(O2CCH3)2]2, yttrium(III) complex has been synthesized by the stoichiometric mixture of YCl3, NaLOMe and NaAc in a 1:1:2 molecular ratio in dry THF solvent and we have determined the structure by X-ray diffraction. The molecule is a dimeric compound, which consists of one tripodal ligand (LOMe=CpCo[P(O)(OMe)2]3) and two bridging acetato (Ac) ligands on each yttrium atom. The acetate ligands of this complex have two different coordination modes, which are μ-κO:κO′-acetato and μ-κO:κ2O′-acetato bound to each yttrium atom.

Selective protonation of a tetraaza macrocyclic copper(II) complex containing two N-acetate pendant arms: short hydrogen-bonded chain structure of the mono-protonated derivative

Abstract Two copper(II) complexes [Cu(H2L3)](ClO4)2 (1) and [Cu(HL3)]n(ClO4)n.nCH3CN (2), in which the pendant N-acetate groups of L3 (2,12-bis(2-carboxymethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14.4.01.18.07.12]docosane) are fully or partially protonated, have been prepared selectively. The complexes have an octahedral coordination polyhedron. The [Cu(HL3)]+ cations of 2 are linked together by strong intermolecular hydrogen bonding interactions (COH⋯OC) between the N-acetic acid and N-acetate pendant arms, forming an one-dimensional polymer; the acetic acid and acetate groups are also coordinated to the metal ion through the oxygen atoms of the carbonyl units. The complexes 1 and 2 are quite stable in the solid states or in non-aqueous solvents, such as nitromethane and N,N-dimethylformamide, but are readily deprotonated to produce [CuL3] in aqueous solutions.

Syntheses and characterization of mono- and di-N-hydroxyethylated tetraaza macrocycles containing eight C-methyl groups and their nickel(II) and copper(II) complexes

Abstract New partially N-hydroxyethylated 14-membered tetraaza macrocycles 1,8-bis(2-hydroxyethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L2) and 1-(2-hydroxyethyl))-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L3) have been synthesized selectively by the one-step reaction of 2,5,5,7,9,12,12,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L1) with 2-hydroxyethyl bromide. The complexes [NiL3]2+, [CuL2]2+, and [CuL3]2+ have been prepared and characterized. The complex [CuL2](ClO4)2 has a square-pyramidal coordination geometry with one apical oxygen atom; only one of the two hydroxyethyl groups is coordinated to the metal ion. Electronic absorption spectra of [CuL3](ClO4)2 containing one hydroxyethyl pendant arm indicate that the geometry is similar to that of [CuL2](ClO4)2. Unexpectedly, the nickel(II) complex [NiL3](ClO4)2 has a severely distorted trigonal bipyramidal coordination geometry with the oxygen atom of the pendant arm at the equatorial position. The NiO bond distance of the nickel(II) complex is shorter, or not longer, than the NiN bond distances. The ligand in [CuL2]2+ is in the RRSS (trans-III) configuration, as usual, whereas that in [NiL3]2+ has the RRRR (trans-V) conformation. The coordination geometry and properties of [NiL3]2+ are quite different from those reported for other related nickel(II) complexes containing one functional pendant arm.

Syntheses and reactivities of new bis(imido)Mo(VI) complexes of hydrotris(3,5-dimethyl-1-pyrazolyl)borate and X-ray molecular structures of [{HB(3,5-Me2C3N2H)3}Mo(Nmes)2X] (X=Cl or OH; mes=2,4,6-trimethylphenyl)

Abstract A chloride substitution reaction of a bis(imido) molybdenum(VI) complex, [Mo(Nmes) 2 Cl 2 (dme)] (dme=1,2-dimethoxyethane) with KTp* (Tp*=hydrotris(3,5-dimethyl-1-pyrazole)borate) in THF resulted in [Tp*Mo(Nmes) 2 Cl] 1 in good yield. The analogous methylated complex [Tp*Mo(Nmes) 2 (CH 3 )] 2 was formed by reaction of 1 with 1 equiv. of CH 3 MgCl in THF, while [Tp*Mo(Nmes) 2 (OH)] 3 was conveniently produced from 2 in the presence of wet methanol under aerobic conditions. The complexes were characterized by 1 H NMR and IR spectroscopy. The molecular structures of complexes of 1 and 3 have been determined by X-ray single crystal analyses. The crystal structures of the complexes show that the three nitrogen atoms of Tp* are not equidistant from the respective Mo(VI) centers. Each Mo(VI) centre of 1 and 3 is in a distorted octahedral coordination geometry with a facially co-ordinated Tp* and two Nmes ligands. The complexes of 1 and 3 contain linear imido ligands

1,3,5-Tri-p-tolyl­biuret

MoOCl2(LOMe) as catalyst, where LOMe is CpCo[P(O)(OMe)2]3, reacts with p-tolyl isocyanate to afford the title compound, C23H23N3O2. The structural features are the intramolecular hydrogen bond forming a six-membered ring and a nearly planar arrangement of the biuret moiety. Each p-tolyl phenyl ring is twisted by approximately 60–80° with respect to the others. The bond lengths N1—C22 of 1.357 (3) A and N2—C23 of 1.333 (3) A indicate that they are partial double bonds.