Xin-Kan Yao

Magnetic interaction in the keto and enol forms of binuclear copper (II) complexes with a Robson-type ligand. X-ray crystal structure of [Cu2 (HL) (μ-N3) (H2O) (C2H5OH) (ClO4)]

Abstract Three dicopper(II) complexes, [Cu2(H2L) (μ-N3)] (ClO4)2 · 1 2 C 2 H 5 OH ( 1 ) , [Cu2(HL) (μ-N3) (H2O) (C2H5OH) (ClO4)] (2) and [Cu2(L) (μ-N3)] · DMF (3) have been synthesized and characterized, where H3L is the pentadentate binucleating ligand 2,6-diformyl-4-methylphenol di(benzoylhydrazone). Because of the existence of a hydrazide structure in the lateral chain, the ligand H3L can lose one, two or three hydrogen atoms to form the keto form (1) or enol form (3) of the binuclear copper (II) complexes, respectively. The crystal structure of 2 has been determined. Crystal dta for 2: monoclinic, space group P21/c, a = 10.967(4), b = 7.684(2), c = 35.724(7) A , β = 90.08°, Z = 4 . The analysis of variable-temperature magnetic susceptibility data indicates that there is an antiferromagnetic interaction between the copper(II) ions in these complexes with the exchange parameters (2J) of −86.8 cm−1 for 1, −132.4 cm−1 for 2 and −176.7 cm−1 for 3. The effect of a tautomeric isomeride on the magnetic interaction was discussed in relation to molecular mechanics and CNDO/2 methods.

Syntheses and molecular structures of complexes formed in the reaction of dichlorobis[π-cyclopentadienyl)-dicarbonyliron]tin(IV) with polydentate o-(nuclear substituted α-hydroxybenzylidenehydrazonomethyl)phenols

Abstract Eleven complexes having the general formula, [π-C 5 H 5 Fe(CO) 2 ] 2 [RC 6 H 4 C(O)N 2 -CHC 6 H 4 O]Sn (R = H, p -NO 2 , p -Cl, p -Br, p -I, p -CH 3 , p -OCH 3 , m -NO 2 , m -OCH 3 , and 3,5-dinitro) have been synthesized. These complexes have been characterized by 1 H NMR, IR and MS, and by elemental analysis. A single crystal X-ray diffraction study (R = o -NH 2 ) confirmed their molecular structures and revealed that the o -(nuclear substituted α-hydroxybenzylidenehydrazonomethyl)phenols are tridentate planar ligands. The crystals are monoclinic, space group P 2 1 / n with a 13.495(4), b 13.058(2), c 18.311(3) A, β 94.90(2)°, V 3214.9 A 3 , Z = 4, D c 1.66 g/cm 3 . Final discrepancy factors of R = 0.033 and R w = 0.039 were obtained for 3075 observed independent reflections. The tin atom has a distorted trigonal bipyramidal coordination. SnFe bond lengths are 2.5421 and 2.5242 A (av. 2.5332 A). In these complexes, the ligands exist in the enol-form.

Synthesis of Me2 Si-η5-C5H4(CO)Fe(CO)2-Fe(CO)-η5-C5H4SiMe2 and a novel reaction between its SiSi and FeFe bonds

Me2Si-η5-C5H4(CO)Fe(CO)2Fe(CO)-η5-C5H4SiMe2 (1) was synthesized by reaction of 1,2-bis (cyclopentadienyl)tetramethyldisilane and pentacarbonyliron. An unexpected product, Me2Si-η5-C5H4Fe(CO)2SiMe 2-η-5-C5H4Fe(CO)2 (2), was obtained from the reaction, which was evidently formed via a novel metathesis reaction between SiSi and FeFe bonds in 1. The molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction studies.

Synthesis and structure of pentacoordinate tin(IV) complexes

Ten complexes formulated as Ph2SnL, where L is RC6H4C(O)N2CHC6H4O with R = H, p-NO2, p-Cl, p-Br, p-CH3, p-OCH3, o-NH2, m-NO2, m-OCH3, and 3,5-dinitro, have been prepared and were characterized by 1H NMR, IR, and mass spectroscopy and elemental analyses. A single crystal X-ray diffraction study of the complex with R=o-NH2 confirms the molecular structure. The crystals are triclinic, space group P1 with a 9.608(2), b 11.826(4), c 21.478(6) A, α 76.17(2), β 76.53(2), γ 88.91(2)°, V 2302.7(4) A3, Z = 4, Dc 1.52 g/cm3. The final discrepancy factors are R = 0.050 and Rw = 0.057 for 3129 observed independent reflections. The tin atom has a distorted trigonal bipyramidal coordination. The two SnO bonds of 2.073(6) and 2.116(6) A, respectively and one SnN bond (of 2.143(7) A)1 are shorter than those found in related complexes. A comparison of the IR spectra of the ligands with those of the corresponding complexes, reveals that the disappearance of the bands assigned to carbonyl unambiguously confirms that the ligands coordinate with the tin in the enol form.

A NEW FRAMEWORK STRUCTURE POLYNUCLEAR COMPLEX OF EUROPIUM NITRATE WITH 1,4-BIS (PHENYLSULFINYL)BUTANE

Abstract A polynuclear europium(III) complex of the formula [Eu(bphsb)1.5(NO3)3]n[bphsb = 1.4-bis(phenylsulfinyl)butane]1734 141 has been prepared and its structure and luminescent properties have been determined by X-ray diffraction and spectral measurements. The structure consists of EuIII ions bridged by bidentate bphsb ligands and coordinated by NO3− groups to make a polynuclear neutral complex. The europium ion is nine-coordinated and the geometry around the EuIII is that of a distorted tricapped trigonal prism. The polynuclear complex has a framework structure with 54-membered macrocyclic rings, each containing six europium ions. The complex exhibits sensitized luminescence that originates from 5D0 state to 7FJ Stark levels.

Synthesis, structures and electrochemical properties of VIB carbonyl complexes containing bis(4-halopyrazol-1-yl)alkanes

Abstract Bis(4-halopyrazol-1-yl)alkanes (1=bis(4-bromopyrazol-1-yl)methane CH2(4-BrPz)2, 2=bis(3,5-dimethyl-4-bromopyrazol-1-yl)methane CH2(3,5-Me2-4-BrPz)2, 3=bis(4-chloropyrazol-1-yl)methane CH2(4-ClPz)2, 4=bis(3,5-dimethyl-4-chloro-pyrazol-1-yl)methane CH2(3,5-Me2-4-ClPz)2) have been synthesized by the reaction of bis(pyrazol-1-yl)methane or bis(3,5-dimethylpyrazol-1-yl)methane with Br2 or SO2Cl2. These ligands react with M(CO)6 (M=Cr, Mo, W) to yield bis(4-halopyrazol-1-yl) methane tetracarbonyl chromium(0), molybdenum(0) and tungsten(0) complexes in reasonable yield. All new compounds have been characterized by elemental analyses, IR, 1H NMR and 13C NMR in the case of tungsten complexes. The electrochemical properties of these complexes studied by the cyclic voltammograms indicate that each compound exhibits one reversible or quasi-reversible couple corresponding to a one-electron oxidation. The structure of CH2(3,5-Me2-4-ClPz)2W(CO)4 determined by X-ray crystallography shows that the six-membered W–N–N–C–N–N metallacycle adopts a boat form.

Trinuclear Cu(II) and Zn(II) complexes bridged by μ3-carbonato anion

The trinuclear Cu(II) and Zn(II) complexes [(CuTPA),(μ3-CO,)] (C104)4(1) and [(ZnTPA),(μ3-C03)](C104)4 (2) (TPA = tri(pyridylmethy1)amine) have been synthesized. X-ray structure analysis of the two complexes proves that CO3 2- anion has an unusual triply bridging ligand, bridging three CuTPA and ZnTPA units respectively, and assembles new trinuclear complexes. The CO3 2- comes from atmospheric CO2. The structure of each trinuclear unit consists of three copper or zinc atoms in a five-coordinate triangular hipyramidal environment. The [(CuTPA)3(μ3-C03) ](C104), compound shows a very weak antifemmagnetic coupling.

Synthesis and molecular structure of a novel binuclear cobalt carbonyl complex with mixed valence Co0CoI(μ-Ph2Ppy)2-(μ-CO)(CO)Cl (Ph2Ppy = diphenylphosphinopyridine)

Abstract Under mild conditions reaction of (Ph 2 Ppy) 2 CoCl 2 or Ph 2 Ppy (Ph 2 Ppy = diphenylphosphinopyridine) and CoCl 2 ·6H 2 O with CO in the presence of zinc powder gave a novel binuclear cobalt carbonyl complex with mixed valence Co 0 Co I (μ-Ph 2 Ppy) 2 (μ-CO)(CO)Cl. The molecular structure of this compound has been determined by X-ray diffraction. The compound crystallized in the monoclinic space group C c (No. 9) with the cell parameters a 17.327(3), b 11.260(2), c 18.212(3) A and β 109.13(1)°. Full matrix least-squares refinement yielded R = 0.034. The formation mechanism of this compound is discussed.

Synthesis, crystal structures and magnetic properties of copper(II) complexes with nitronyl nitroxide

Abstract Two novel adducts of formula [Cu(pfpr) 2 (NITmNO 2 )] 2 (I) and Cu(hfac) 2 (NITmNO 2 ) (II), where pfpr=pentafluoropropionate, hfac=hexafluoroacetylacetonate and NITmNO 2 =2-(3-nitrophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, have been synthesized. Compound (I) is the first example of copper (II)–nitroxide complexes bridged by pfpr. Its structure consists of binuclear units with the tetrakis(pentafluoropropionate) bridging two copper ions. Each copper ion has a distorted trigonal–bipyramidal coordination. Compound (II) is a mononuclear complex with a five-coordinated distorted square–pyramidal environment. The variable temperature magnetic susceptibilities show that there are antiferromagnetic interactions between copper ions and radicals for compound (I), and compound (II) is diamagnetic.

Synthesis, structure and magnetic properties of a quasi-one-dimensional copper(II) compound. An unusual oxalato-bridged copper dimer

Abstract A new compound [Cu(Him)2(ox)]2[Cu(Him)2(H2O)]2 (Him=imidazole, ox=dianion of oxalic acid) has been prepared and structurally determined. The structure consists of quasi-one-dimensional chains built from two different neutral [Cu(Him)2(ox)]2 and [Cu(Him)2(H2O)(ox)]2 units linked by hydrogen bonds. Two centrosymmetrically related copper ions in the former unit are five-coordinated by two nitrogen atoms from the imidazole ligands and two oxygen atoms from the oxalate anion occupying the basal plane and the oxygen atom of another chelating oxalate situated at the apical position with a weak contact of 2.837(2) A. The coordination environment of the other two copper ions connected by O–H · · · O hydrogen bonds in the other unit can be described as a distorted square pyramid, with two oxygen atoms of the oxalate ion and two nitrogen atoms from the imidazole ligands in the basal plane and one oxygen atom of the coordinated water molecule in the apical position. The (Him)N–H · · · O(ox) hydrogen bonds connect the adjacent units to give rise to a quasi-one-dimensional structure. The room-temperature ESR study gives a g↑ value of 2.07 and a g∥ value of 2.23. From magnetic susceptibility measurements the compound was found to exhibit a weak antiferromagnetic interaction (J=−2.64 cm−1) between the copper(II) ions through the Cu–O–Cu pathways.