Synthesis , Spectral Characterization and Ligation of N-[ 2-( Phenylseleno ) ethyl ] phthalimide

PhSeNa generated in situ by reduction of PhSeSePh, with sodium borohydride on reaction with N-(2-bromoethyl) phthalimide in N2 atmosphere results in the formation of N-[2-(phenylseleno)ethyl]phthalimide (L). The title compound has been characterized by elemental analysis, FT-IR, H and C NMR techniques. The crystal structure of L has been solved by direct methods and refined by full-matrix least squares. The ligand L crystallize in the monoclinic space group. Selenium forms two Se-C linkages, one is due to Se-Calkyl and the other one to Se-Caryl. Further, the ligation reaction of L with complex 1 is also explored whose identities are characterized by spectroscopic techniques.


Introduction
There is current interest in the chemistry of a variety of polydentate organochalcogen ligands due to their hemilabile nature, and the possiblilty of using their metal complexes as precursor for II-VI semiconductors [1][2][3][4].The synthesis and characterization of N-{2-(4methoxyphenyl telluro) ethylphthalimide} [5], potentially [Te, N, O 2 ] type donor along with its palladium [5] and ruthenium complexes [6] were studied.Recently various bidentate heteroleptic ligands [7] containing donor groups (N, S and N, Se), have been prepared which offer opportunities in catalytic cycle of aryl bromides.In our previous study, we reported the synthesis, characterization, and crystal structure of the first example of selenium containing acetate salt (3-Phenylseleno) propylammonium acetate salt [8].We have also reported the cleavage of L 1 in two different ways upon reaction with selected metal salts [8].In continuation of our studies on (Te, N, O) and (N, S and N, Se) donors, we have synthesized a novel (Se, N, O) donors.L 1 was characterized by spectral and X-ray analysis.

Materials
Diphenyl diselenide [9], was prepared according to the published method, N-(2-bromoethyl) phthalimide was used as received from Aldrich.Selenium powder and sodium borohydride were purchased from CDH (India).All glassware were cleaned with acetone, followed by copious rinsing with distilled water before rinsing with distilled water before drying at 150˚C in oven for a few hours.

Equipment
All reactions involving air sensitive compounds were performed under nitrogen atmosphere.The C, H and N analysis were carried out with an Elementar Vario EL III analyser. 1H and 13 C NMR spectra were recorded with a JEOL AL300 FT NMR spectrometer at 300 MHz and 75.45 MHz, respectively, in CDCl 3 and DMSO(d 6 ) as solvents (tetra methyl silane (TMS) as internal standard).IR spectra in the range of 4000 -400 cm −1 were recorded on a Shimadzu Prestige 21 FT-IR spectrometer as KBr pellets.The melting point was determined in open capillary are reported as such.

Ligand Synthesis
Synthesis N- [2-(phenylseleno)ethyl]phthalimide (L 1 ).To an aqueous THF solution (20 mL THF + 0.2 mL H 2 O) of diphenyl diselenide (3.14 g, 10 mmol) and NaOH (0.80 g, 20 mmol) under N 2 atm, NaBH 4 (0.75 g, 20 mmol) was added in pinches.The yellow color of the diselenide darkened and then gradually faded to colorless.To this colorless solution, N-(2-bromoethyl)phthalimide [5.08 gm, 20 mmol] in THF (20 mL) was added dropwise and the solution was stirred for 24 h at room temperature.It was hydrolyzed with 100 mL water and extracted into 200 mL chloroform, washed with 100 mL water and dried over anhydrous magnesium sulphate.The extract was concentrated to 5 mL under reduced pressure, then washed with diethyl ether to remove the precursor diphenyl diselenide, and kept overnight at room temperature.The resulting white precipitate was recrystallized with chloroform-diethyl ether mixture (1:2) and dried in vacuo.It was followed by crystallization with slow evaporation of a CHCl 3 /MeOH solution to yield a transparent crystals.Yield: 70% Mp: 120˚C Found:

Crystal Structure Analysis
X-ray data for N- [2-(phenylseleno)ethyl]phthalimide were collected with an Oxford Diffraction Gemini R CCD area detector using CrysAlisPro software and graphite-monochromated MoKα (l = 0.71073 Å) at 200 (2) K.The size of crystal used for data collection was 0.55 × 0.35 × 0.12 mm 3 .The structure was solved by direct methods using SHELXS97 [10] and all of the non-hydrogen atoms were refined anisotropically by full matrix least-squares on F 2 using SHELXL97 [10].The hydrogen atoms were placed in their calculated positions and included in the refine-ment using the riding model.An absorption correction was performed using CrysAlis RED and all calculations were performed using SHELXTL [11].

Results and Discussion
The reaction given in Scheme 1 produce N-[2-(phenylseleno)ethyl]phthalimide (L 1 ), which remain stable under ambient conditions for 2 -3 months.It is soluble in ethanol, methanol, chloroform and dichloromethane.It was characterized by elemental analysis, IR, 1 H, 13 C NMR and single crystal structure.In the IR spectra of L 1 due to presence of electronegative selenium, band of amide group is shifted to higher wavenumber 1708 cm −1 in comparison to the precursor N- [2-(bromo) ethyl] phthalimide at 1681 cm −1 .The bands at 1170 and 512 cm −1 are attributed to ν (C-N) and ν (Se-CH 2 ).The 1 H and 13 CNMR spectra of L 1 display the expected resonances and peak multiplicities.1:1 heterobimetallic adducts of L 1 with HgCl 2 was obtained by stirring a mixture of the two components in methanol: chloroform mixture spectively.The absorption due to ν (C=O) remain almost unaffected, indicating that L 1 in complex 1 is coordinated through N and Se.The 1 H and 13 C NMR spectra of complex 1 are normal.In d 10 system, coordination shifts in the NMR spectra is found to be insignificant [8].In 1 H NMR spectrum of complex 1 the downfield shift of Se-CH 2 and N-CH 2 signals clearly establishes the coordination through Se and N to the metal atom.In the 13 C { 1 H} NMR spectra of complex 1, the deshielding of Se-CH 2 and N-CH 2 signals by 0.42 and 1.16 ppm respectively with respect to those of free ligand L 1 , also argues for the coordination of the selenium and the nitrogen atom to the metal ion.Thus, the IR and NMR data shows that the ligand L 1 ligates through (Se, N) in a bidentate mode [12][13][14] to the metal salt and support from previous work, the following most possible structure has been proposed on the presumption that geometry of complex 1 is tetrahedral (Figure 1) The molecular and that of the unit cell, as determined by X-ray diffraction on a single crystal of N-[2-(phenylseleno)ethyl]phthalimide, are shown in Figures 2 and 3.It may act as a (Se, N) donor easily and perhaps (Se, N, O) donor also in bimetallic complexes.L 1 crystallizes in the   monoclinic space group P 21/n with unit cell parameters a = 5.0586 (5), b = 10.1316(8), c = 27.050(5), Å = 93.250(11)˚, Z = 4. Crystal and experimental data for L 1 are listed in Table 1.Bond lengths and bond angles are all within expected ranges, (see Table 2).In the present compound selenium is regarded as in oxidation state +2.The length of the C-Se bonds, 1.919 (3) and 1.952 (3)  Ǻ and the angle between these two bonds, C-Se-C are consistent [15].The Se-C(Ar) bond distance is somewhat shorter than the Se-C(alkyl) distance as expected [16].

Conclusion
We have shown that NaBH 4 can be used as reduction system to generate an organochalcogen anion.This anion reacts in a SN 2 reaction on N- [2-bromoethyl]phthalimide to produce N- [2-(phenylseleno)ethyl]phthalimide (L 1 ) under mild conditions.These organochalcogen derivatives, L 1 , was used to synthesize a metal complex 1, from HgCl 2 .L 1 act as a polydentate ligand containing oxygen or nitrogen as a hard donor.And chelate 1 was characterized as 1:1 complex by various spectroscopic techniques (IR, FAB mass, 1 H and 13 C NMR).

Supplementary Material
For L 1 , crystal data, structural information (geometric bond distances, bond and torsion angles; hydrogen bonding) & refinement data are provided.Crystallographic data (CIF) for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre and allocated the deposition numbers CCDC 766004 for L 1 .These data can be obtained, free of charge via www.ccdc.cam.ac.uk/data_request/cif, by sending an e-mail to data_request@ccdc.cam.ac.uk., from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax; +44 1223 336033

Figure 2 .
Figure 2. The molecular structure of the complex, C 16 H 13 -NO 2 Se, showing the atom numbering scheme and 30% probability displacement ellipsoids.Symmetry transformations used to generate equivalent atoms.

Figure 3 .
Figure 3.The molecular packing for C 16 H 13 NO 2 Se, viewed down the axis.