Michio Nakashima

Synthesis and crystal structure of a novel hexanuclear Zr(IV) complex with 1,10-phenanthroline including carboxylato, hydroxo, and oxo bridging

Abstract A novel hexanuclear Zr(IV) complex, [Zr 6 (O) 6 (OH) 2 (Ph 2 CHCOO) 10 (phen) 2 ]·4CH 3 CN ( 1 ), where phen denotes 1,10-phenanthroline, has been prepared and characterized on the basis of elemental analysis, infrared-spectroscopy measurements, and X-ray crystallography. Complex 1 resides on a crystallographic inversion center, thus making only three of the six zirconium ions unique. The six zirconium ions are arranged in apices of an octahedron. One Zr(IV) metal ion (Zr1) is individually joined with two Zr(IV) metal ions (Zr2, Zr3) by one syn–syn bridging carboxylate group, and Zr1 has three μ 3 -O and one μ 3 -OH bridges through Zr2 and Zr3. The Zr2 atom is also connected by one syn–syn bridging carboxylate group through Zr3*. Moreover, Zr1 is coordinated by two nitrogen atoms of a bidentate 1,10-phenanthroline group with eight coordination. Besides these, Zr2 is coordinated by one carboxylate of a bidentate–chelate type, completing the eight coordination. The Zr3 atom is coordinated by one monodentate carboxylate oxygen, consequently has a novel seven coordination.

CRYSTAL STRUCTURE AND CHARACTERIZATION OF BINUCLEAR COPPER(II) COMPLEX WITH N- (2-HYDROXYPHENYL)-3-METHOXYCARBONYL -4,6-DIMETHYLSALICYLAMIDE

The binuclear copper(II) complex of N -(2-hydroxyphenyl)-3-methoxycarbonyl-4,6-dimethylsalicylamide (H 3 Lmc) was obtained as the tetrapropylammonium salt (NPr 4 ) 2 [Cu 2 (Lmc) 2 ] NPr 4 + = tetrapropylammonium ion). The structure was solved by single-crystal X-ray crystallography, which demonstrated that two copper ions are bridged by the phenolic oxygen of the ‘aminophenol’ moiety. Cryomagnetic investigation (80–300 K) revealed a significant antiferromagnetic spin exchange through the bridging oxygen. Cyclic voltammetry showed two irreversible oxidation waves at +.40 and +0.67 V (versus SCE).

Synthesis and characterization of a manganese(III) complex with a new unsymmetrical chelating ligand

Abstract The new unsymmetrical chelating ligand of 4,6-dimethyl-3-(4,4-dimethyl-2-oxazolinyl)- N -(2-hydroxy-1,1-dimethylelthyl) salicylamide (H 3 LOx) and the mononuclear manganese(III) complex, [Mn(OAc)(H 2 LOx) 2 ] ( 1 ), have been synthesized and characterized by X-ray structural analyses, elemental analyses and cyclic voltammograms. The crystal structure analyses have revealed that the H 3 LOx ligand functions as a bidentate chelate with a deprotonated phenolic oxygen atom and nitrogen atom of an oxazolinyl ring.

Crystal Structure and NQR Studies of Compounds (RH)[ZnBr3(R)], (RH)(2)[ZnBr4] and [ZnBr2(R)(2)] (R = Py, n-MePy: n=2, 3, 4); on the Dominant Stability of the Monoanionic Complexes over the Dianionic and Neutral Species

The monoanionic complexes (C5H5NH)[ZnBr3(C5H5N)] (1) and (n-CH3C5H4NH)[ZnBr3(n- CH3C5H4N)] (n = 2 (2), 3 (3), 4 (4)) were prepared by crystallization from ethanol solutions through redistribution reactions between the corresponding dianionic complexes (C5H5NH)2[ZnBr4] (5) and (n-CH3C5H4NH)2[ZnBr4] (n = 2, 3 (6), 4 (7)) and the neutral complexes [ZnBr2(C5H5N)2] (10) and [ZnBr2(n-CH3C5H4N)2] (n = 2 (8), 3, 4 (9)). The crystal structures of 1, 4, 9, and 10 were determined; 1: triclinic, P1, a = 7.6957(5), b = 7.7975(4), c = 12.4768(8) Å , α = 90.857(5), β = 95.917(5), γ = 107.899(6)°, Z = 2, 150 K; 4: monoclinic, P21/c, a = 14.8369(6), b = 13.9504(5), c = 8.0041(3) Å , β = 96.318(4)°, Z = 4, 299 K; 9: monoclinic, P21/c, a = 14.2883(5), b = 8.0269(3), c = 13.6031(5) Å , β = 100.581(4)°, Z = 4, 150 K; 10: monoclinic, P21/c, a = 8.7388(5), b = 17.9730(10), c = 8.5452(5) Å , β = 100.024(6)°, Z = 4, 300 K. The cation and anion are paired up via bifurcated hydrogen bonds in the structure of 1 and via a normal N-H· · ·Br hydrogen bond in the structure of 4. 81Br NQR resonance lines coinciding in number with the Br atoms in the chemical formulae were observed for the compounds 1 - 5 and 7 - 9 throughout the temperature range from 77 to ca. 320 K. The comparison between the net charges on the Br atoms obtained by the Townes-Daily analysis or by the Mulliken population analysis seems to indicate that the formation of the intermolecular N-H· · ·Br hydrogen bonds and the π-π and the CH3-π interactions in the crystal structures of the monoanionic complexes are the driving forces to the redistribution reactions Graphical Abstract Crystal Structure and NQR Studies of Compounds (RH)[ZnBr3(R)], (RH)2[ZnBr4] and [ZnBr2(R)2] (R = Py, n-MePy: n = 2, 3, 4); on the Dominant Stability of the Monoanionic Complexes over the Dianionic and Neutral Species

Crystal Structure, NQR and DSC Studies of Tetrabromocadmates(II): [4-H2NC5H4NH]2CdBr4 · H2O and [2,3,5,6-(CH3)4C4N2H2]CdBr4

Abstract 4-Aminopyridinium tetrabromocadmate(II) monohydrate (1) crystallizes in the orthorhombic space group Pbcm with a = 6.876(2), b = 14.089(2), and c = 18.845(2) Å , Z = 4, T = 296 K. In the crystal structure, a [CdBr4]2− anion, a 4-aminopyridinium cation, and a water molecule are alternately connected into chains by hydrogen bonds N-H···Br and O-H···Br. 2,3,5,6- Tetramethylpyrazinium tetrabromocadmate(II) (2) crystallizes in the orthorhombic space group P212121 with a = 14.640(12), b = 15.615(7), c = 6.686(5) Å , Z = 4, T = 296 K. In the crystal structure, a [CdBr4]2− anion and a 2,3,5,6-tetramethylpyrazinium cation are interconnected by bifurcated hydrogen bonds N-H· · ·2Br and form infinite chains. 81Br NQR spectra with three lines with an intensity ratio of 1 : 1 : 2 (77 K ≤ T ≤ ca. 325 K) and four lines with an intensity ratio of 1 : 1 : 1 : 1 (77 K ≤ T ≤ ca. 330 K) were observed for crystalline 1 and 2, respectively, which are consistent with the crystal structure data. DSC measurements showed the existence of thermal anomalies at high temperatures in both 1 and 2.