Synthesis and Structural Analysis on A Copper（Ⅱ）Compound 1，2－Bis－ （salicylidenehydrazo）－1，2－diphenyl－ethane

LI Zai－gao （College of Chemistry and Environmental Engineering，Yangtze University，Hubei Jingzhou434023）

1 Introduction

One of the interests toward unsaturated and coordinated mononuclear Cu （Ⅱ）complex of aldamine ligand takes the sort for mimic of copper （Ⅱ）－containing enzyme［1－2］.The remaining coordination site of Cu （Ⅱ）allows a ligation of substrate and so promises the catalysis［3］.So far，a huge number of such complexes have been synthesized and proven to be operative，however，to our knowledge，most of them have amine－derived Schiff base ligand.Relatively，those with hydrazone as ligand are much less reported.Recently，Xiang and his co－workers have reported a series of Cu （Ⅱ）complexes containing the hydrazone ligands.Two different pathways including the ring－closure of hydrazone to form［1，2，3］－triazole ligand and novel coupling reactions of two molecules of hydrazoles with one molecule of primary alcohol have been found.The Cu （Ⅱ）ions have been proved as the important catalyst for promoting these two novel reactions［4］.In recent work，we have successfully isolated the first example of Cu （Ⅰ）complex containing［1，2，3］triazolo ［1，5－a］quinoline ligand，which further confirms that Cu （Ⅱ）ion is crucial for promoting the reactivity of hydrazone［5－6］.Thomas and d’Hardemare et al.have recently investigated the redox activity of a series of Zn（Ⅱ）complexes containing azo or hydrazone ligands and their study shows that hydrazyl radical species could be generated by one－electron oxidation／reduction，Which inspires us to investigate the possible function of metal ion towards the reactivity of coordinated hydrazones［7］.Herein，we investigate the reactivity of a variety of hydrazones towards the aerial oxidation in the presence of Zn （Ⅱ）ion and further illustrate the function of metal ions by comparison with Cu （Ⅱ）ion［8］.

2 Experimental

2.1 Reagents and instrumentation

All the solvents are purified by conventional procedures and distilled prior to use.All other chemicals are of reagent grade and used without further purification.All manipulations are performed without precaution to exclude air or moisture unless otherwise stated.Infrared spectra from KBr pellets are collected on a Nicolet Avatar 360FTIR spectrometer in the range 4000～400cm－1.Electrospray ionization mass spectrometry（ESI－MS）is performed using a PE－SCIEX API 365triple quadruple mass spectrometer.Elemental analyses of C，H and N are determined with a Perkin－Elmer 2400C Elemental Analyzer.Magnetic measurements are performed at room temperature using a Sherwood magnetic balance（MarkⅡ）.

2.2 Synthesis of［CuⅡ （BSDPE）］（1）

H2L is prepared by the literature method，preparation of 1∶CuCl22H2O （0.034g，0.2mmol）dissolved in 10ml ethanol is added drop by drop to BSDPE（0.065g，0.2mmol）in ethanol（10ml）.The mixture are stirred for 10min，adjust pH to 8with NEt3，then refluxed for 6h，followed by evaporating the filtrate at ambient condition.Crystals are obtained in about 60%yield.Analysis calculated for C56H40Cu2N8O4：C 66.13，H 3.93，N 11.02%；found：C 66.00，H 3.56，N 11.22%.IR（KBr，cm－1）：3378 （m），3051 （w），3015 （w），1601 （s），1580 （m），1523 （m），1442 （m），1147 （m），906（m），755（m），681（m）.

2.3 Structure determination

Measurements are collected on a Bruker CCD diffractometer using graphite－monochromated MoKa radiation（λ＝0.71073Å）for all the compounds.Details of the intensity data collection and crystal data are given in Table 1.Absorption corrections were done by the multi－scan method.The structures are resolved by the heavy－atom Patterson method or direct methods and refined by full－matrix least－squares using SHELX－97and expanded using Fourier techniques.All non－hydrogen atoms are refined anisotropically.Hydrogen atoms are generated by the program SHELXL－97.The positions of hydrogen atoms are calculated on the basis of riding mode with thermal parameters equal to 1.2times that of the associated C atoms，and participated in the calculation of final R indices.All calculations are performed by using the teXsan crystallographic software［9－11］.

3 Results and discussion

3.1 Syntheses and characterizations of ligand H2BHS and 1

Fig.1 The synthetic route for 1

The mixture of salicylaldehyde，hydrated NH2NH2and diketone are heated at reflux with the mole ratio 2∶2∶1in ethanol afforded yellow microcrystalline solids with high yield （90%）.The synthetic procedure is well comparable with most related ligands.IR spectrum of H2BHS shows that the presence of the（C═ N）stretching band is at 1618cm－1and the disappearance of strong peak is at 1685cm－1that is assigned to the（C═ O）stretching band of deketone，suggesting the formation of ligands H2BHS.In a reaction of CuCl2with ligand H2BHS in methanol，the title complex 1is obtained as blue crystals，which are isolated as air－stale，black microcrystalline solid with 70%yield.The IR spectrum of 1agrees with the constitution illustrated by the schematic structure（Fig.1） ═.The C N bonds are symbolized by the absorptions at 1601cm－1and the aryl rings stretching band are in the range of 1598～1806cm－1.Compound 1has room temperature magnetic moment（solid sample，Gouy method）ofμeff＝1.867μB，consistent with its formulation as d9Cu （Ⅱ）complex.This result also indicates that the oxidation state of Cu （Ⅱ）salt remained unchanged.As shown in Figure 1，the ligand H2BHS have two O atoms and four N atoms available for coordination with metal ions.

3.2 Single crystal of 1

Slow evaporation of methanolic solution of 1for 1week afforded dark block crystals suitable for X－ray determination.The crystal structure of 1has been determined by X－ray crystallography.Compound 1 crystallizes in monoclinic P－1group system.Fig.2is the structure of 1revealed by X－ray single crystal diffraction.The independent packing unit of 1is shown to consist of a pair of motifs distributed symmetrically around an inversion center.As the coordination environments of two Cu centers are similar，only one of them is discussed herein.The structural refinement of 1is summarized in Table 1.Selected fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters（Å2）are listed in Table 2and selected bond length（Å）and bond angle（°）are listed in Table 3.The motif of note contains a four－coordinated Cu （Ⅱ）in a surrounding geometric between planar square and tetrahedral with the angles，N1－Cu2－O4＝154.24and N3－Cu2－O3＝144.92°.The intra－cycle angles，N1－Cu2－N3 （95.76°）and N－Cu－O（93.34，93.66°）are systematically larger than 90°.In comparison with planar Cu （Ⅱ）complexes of salicylhydrazone，the O－Cu（1.874Å，1.869Å）and N－Cu（1.941，1.997Å）bonds of 1are some shorter for the less repulsion around Cu （Ⅱ）.The Cu－N and Cu－O bond distances are well comparable with most related Cu （Ⅱ）complexes containing the similar lgands.However，the coordination geometry of Cu（Ⅱ）center is significantly different from that with the Cu （Ⅱ）center with N4ligations in the in－situ formed bis （hydrazone）ligands，where the metal centers are in the distorted square pyramidal coordination sphere.Extensive supra－molecular interactions are found in the packing diagram of this compound，which connectes the discrete structural units into a 3－D supra－molecular network.As demonstrated in Fig.3，there are extensiveπ－πstacking among the phenyl rings of H2BHS with average centroid－to－centroid distance of 3.887（1）Å.The motifs are orderly arranged along a axis （Table 1－3）.

Fig.2 ORTEP（Johnson，1976）plot of the two independent motifs of 1.with partial atoms numbered.Displacement ellipsoids are drawn at the 30%probability level.H atoms are shown as spheres of arbitrary radii

Fig.3 The packing diagram of complex 1

In conclusion，a new Cu （Ⅱ）complex bearing the H2BHS ligand have been obtained.The ligand binds the metal center via two N and two O atoms as the tetradentate ligand.The coordination geometry of Cu （Ⅱ）is significantly different the previously reported Cu （Ⅱ）compounds containing the similar bis （hydrazone）ligand.The different coordination modes may suggest the different reactivity with respect to the air－oxidation.Thus，the present compound may be a good candidate for primary alcohol oxidation via O2in the air.

Table 1 Data collection of compound 1

Table 2 Selected fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters（Å2）

Table 3 Selected geometric parameters（Å，o）

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