Zhang Tonglai, Zhang Jianguo, Zhang Zhigang, Wei Zhaorong, Yu Kaibei^#
(Department of Mechano-electric Engineering, Beijing Institute of Technology, Beijing 100081; ^#Analysis and Measurement Center, Chengdu Branch of the Chinese Academy of Science, Chengdu 610041, China)

Received Feb. 20, 2000.

Abstract A new coordination compound was prepared by mixing aqueous solution of carbohydrazide and manganese perchlorate. It was also characterized by elemental analysis, IR and DSC analysis. The molecular and crystal structure of perchlorate tricarbohydrazide Manganese (II) was determined by X-ray crystallography. The crystalline is monoclinic with space group P2₁/n. The coordination compound could be expressed in the formula of [Mn(CHZ)₃](ClO₄)₂ with crystal parameters: a = 1.0197(2)nm, b = 0.8593(1)nm, c = 2.1412(3)nm, b= 100.86, V = 1.8426(5)nm³, Z = 4. The results suggest that all carbohydrazide molecules coordinated with central ion as bidentates through oxygen atom of carbonyl group and one terminal nitrogen atom, and linked with Manganese to form three five-number rings.
Keywords manganese perchlorate, carbohydrazide, preparation, molecular structure, crystal structure

Carbohydrazide is an azotic ligand with lone electron pairs. It may coordinate with many metal ions as monodentate or multidentate ^[1,2]. Because the ramification of hydrazine possesses strong reduction ability, it has been used to design a variety of compounds with explosive properties. This kind of coordination compounds of carbohydrazide arouses great interests especially in recent years in primary explosives, propellants and high explosives ^[3-6]. As a part of our research work, we now present the preparation method and the structure determination of perchlorate tricarbohydrazide Manganese (II).

1 EXPERIMENTAL
1.1 Preparation 
All materials and reagents used in our experiments are reagent grade. The carbohydrazide was commercial product and recrystallized in distilled water. The product is white sheet crystal with a melting point of 155°C.
    2.97g of carbohydrazide was dissolved in 20ml distilled water. The solution was put into a reactor and heated to 60-70°C in water bath. The solution of manganese perchlorate was obtained by reacting manganese carbonate (1.17g, 0.01mol) and equivalent perchlorate acid ^[5,6]. Its filtrate was then dropped into the reactor with violent stirring and allowed to react for 35 mins. The reaction mixture was then cooled to room temperature and filtered to obtain white crystal product, which was washed with distilled water and dried in vacuum oven at 60°C for 2 hrs. The yield was 76%, M.P. 265-266.3°C (d). The product is a potential strong explosive material and must be treated with great care.
    Controlled evaporation process was used to culture single crystals within a few days. The content of carbon, nitrogen and hydrogen was analyzed by Carlo Erba 1106 automatic micro-analyzer. Found: C, 6.85, H, 3.50, N, 32.07. Calcd.: C, 6.87, H, 3.46, N, 32.08.
1.2 Infrared absorption spectrum analysis
Infrared absorption spectra were recorded on Perkin-Elmer 683 FT-IR spectrometer with KBr tablets. The absorption peaks and assignments are as follows: ＝3348 cm^-1, ＝3307 cm^-1, =1606 cm^-1. The peaks of 1144, 1086 and 629 cm^-1 are assigned to perchlorate ion.
1.3 DSC analysis
DSC experiments were carried out on model CDR-1 differential scanning calorimeter with an aluminum sample pan. The conditions of DSC were as follows: sample mass about 1 mg, heated rate 10°C/min, static air atmosphere, α-Al₂O₃ reference sample, Ni/Cr-Ni/Si thermal-couple.
   The decomposition processes of the title compound were recorded in the range of 30-500°C under linear temperature increase condition. The measurement results showed that the thermal decomposition processes comprise three major stages on the DSC curve. The first stage was a weakly endothermic peak, resulting from melting process of the compound from 263.3°C to 268.7°C. The second stage was an acute exothermic process and showed an acute and strong pinnacle from 268.7°C to 295.6 with maximal at 276.7°C. The third stage showed an overlapped exothermic process from 298.8°C to 330.9°C, and the two peaks appear at 309.8°C and 315.6°C. The DSC results verified that the decomposition process is a very strong exothermic reaction similar to other explosives.
1.4 Crystal structure determination
A single crystal with dimensions of 0.50*0.48*0.28 mm³ was used to collect the diffraction intensity data on a Siemens P4 diffractometer fitted with graphite-monochromated Mo K_a radiation, l=0.071073nm. The measurement was carried out at room temperature. The w scan method was employed and a total of 4247 reflections were collected in the range of 1.94°<q<26.00°. The scan range is: 0< h <12, 0< k <10 and 26 <l <25, in which 3631 independent reflections were obtained, among which 2789 with I＞2σ(I) were used for the determination of crystal structure and refinement. The crystal of [Mn(CHZ)₃](ClO₄)₂ is monoclinic with space group P2₁/n with a = 1.0197(1)nm, b = 0.8593(1) nm, c = 2.1412(1) nm; b=100.86°, V = 1.8426(5) nm³, Z = 4, Dc =1.889 g/cm³, μ=1.089 mm^-1, F(000)=1068.

Table 1 Experimental data and summary of intensity collection and structure data

w=1/[σ²(F₀²)+(0.0929P) ²+0.94P], P=[ F₀²+2F_C²]/3

Table 2 Atomic Coordinates (*10⁴) and Equivalent Isotropic Displacement Parameters (nm²)

Table 3 Selected Bond Distances

    The structure was solved by direct method and refined by full-matrix least-squares methods based on F with anisotropic displacement parameters for the non-H atoms. The positions of the H atoms were found in differential Fourier maps and refined using isotropic displacement parameters. A semi-empirical extinction correction was applied to Fc. The refinement continued to final R=0.0488 and R_w=0.1393 for 3631 independent reflections. The structure solution and refinement are accomplished by using the Siemens SHELXTL 5.03 programs package with the Eclipes/140 computer. Crystal data are listed in Table 1. Fractional atomic coordinates and thermal parameters of [Mn (CHZ)₃](ClO₄)₂ are given in Table 2. Selected bond lengths and angles are provided in Table 3 and Table 4.

2 RESULTS AND DISCUSSIONS
The molecular structure of perchlorate tricarbohydrazide manganese (II) and the atom labeling scheme are illustrated in Figure 1. The results show that there are three carbohydrazide molecules in every molecule. Every carbohydrazide acts as a bidentate and coordinated to manganese cation with its oxygen atom of the carbonyl group and the terminal nitrogen atom so that they formed a chelating ring with five members. There are three such rings in the molecule. The coordination number of the central atom is six with a octahedral configuration. The atoms forming every five-member ring take on the favorable coplanarity.

Table 4 Selected Bond Angles

    Due to these three chelate-rings, the molecular structure of [Mn(CHZ)₃](ClO₄)₂ possesses particular stability. Because every carbohydrazide molecules has one free diazanyl in the molecular structure, they served as spring between molecules that makes the molecular structure possess good flexibility of which is accordant with its lower mechanical sensitivity^[7]. The outer spheres are two perchlorate anions. They combined to inner sphere by static electricity.

Fig. 1 The molecular structure of [Mn(CHZ)₃](ClO₄)₂

Fig. 2 Projection of the crystal packing of [Mn(CHZ)₃](ClO₄)₂

    The molecular packing in the unit cell of perchlorate tricarbohydrazide manganese (II) is illustrated in Figure 2 in which the hydrogen atoms have been removed for clarity. It is clear that the molecule exits in stakes wherein each stake is composed of molecules generated by inversion center without any intermolecular contact.

3 CONCLUSION
The obtained results show that the coordination compound is expressed as [Mn(CHZ)₃](ClO₄)₂ . All of the carbohydrazide molecules serve as bidentates to chelate with manganese cation forming three five-member rings, which let the coordination compound possess very stable structure. The higher nitrogen content of the ligand and stronger oxidization ability of perchlorate make the compound give out high energy output when it is ignited. Consequently, perchlorate tricarbohydrazide manganese (II) would be a kind of prominent and potential energetic material for mining applications.

REFERENCES
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[3] Fogelzang A E. Mater. Res. Symp. Proc., 1996, 418-422.
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[5] Lu C H, Zhang T L, Wei Z R et al. Chinese Journal of Inorganic Chemistry (Wuji Huaxue), 1999, 15 (3): 377-383.
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[7] Lu C H, Zhang T L, Wei Z R et al. Proceedings of the third International Autumn Seminar on Propellants, Explosives and Pyrotechnics Sichuan Publishing House of Science of Technology, Chengdu, 1999, 33-36.　

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