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 [1-4]. The synthesis and characterization of N-{2-(4methoxyphenyl telluro) ethylphthalimide} [5], potentially [Te, N, O₂] 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 L¹ 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. L¹ was characterized by spectral and X-ray 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 mm³. 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 F² using SHELXL97 [10]. The hydrogen atoms were placed in their calculated positions and included in the refinement using the riding model. An absorption correction was performed using CrysAlis RED and all calculations were performed using SHELXTL [11].

The reaction given in Scheme 1 produce N-[2-(phenylseleno)ethyl]phthalimide (L¹), 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, ¹H, ¹³C NMR and single crystal structure. In the IR spectra of L¹ 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-CH₂ ). The ¹H and ¹³CNMR spectra of L¹ display the expected resonances and peak multiplicities. 1:1 heterobimetallic adducts of L¹ with HgCl₂ was obtained by stirring a mixture of the two components in methanol: chloroform mixture (1:1) at r.t. (Scheme 2). Complex 1 remains stable under ambient conditions for 2 - 3 months. It is soluble in ethanol, methanol, chloroform and dichloromethane. It was characterized by elemental analysis, FAB mass IR, ¹HNMR and ¹³CNMR. FAB mass spectrum of complex 1 confirms its monomeric character and the presence of a 1:1 metal:ligand stoichiometry in the compound. The molecular ion peak [M + H] is observed at m/z 604 with a very low intensity. The base peak at m/z 174 corresponds to [L¹-SePh]. The peaks at m/z 533 [MH-2Cl] and m/z 254 [L¹-Ph] are observed with low intensity whereas the peaks at m/z 568 [MH-Cl] and 331 [L¹] observed with abundance. In the IR spectra of complex 1, the absorption due to ν (C-N) and ν (Se-CH₂) are shifted to lower frequency and appear at 1153 and 501 cm⁻¹ re-

Scheme 1. Preparation of N-[2-(phenylseleno)ethyl]phthalimide (L¹).

Scheme 2. Preparation of complexes 1.

spectively. The absorption due to ν (C=O) remain almost unaffected, indicating that L¹ in complex 1 is coordinated through N and Se. The ¹H and ¹³C NMR spectra of complex 1 are normal. In d₁₀ system, coordination shifts in the NMR spectra is found to be insignificant [8]. In ¹H NMR spectrum of complex 1 the downfield shift of SeCH₂ and N-CH₂ signals clearly establishes the coordination through Se and N to the metal atom. In the ¹³C {¹H} NMR spectra of complex 1, the deshielding of Se-CH₂ and N-CH₂ signals by 0.42 and 1.16 ppm respectively with respect to those of free ligand L¹, 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 L¹ ligates through (Se, N) in a bidentate mode [12-14] 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. L¹ 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 L¹ 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)

Table 1. Crystal data and structure refinement for N-[2- (phenylseleno)ethyl]phthalimide.

Table 2. Bond lengths [Å] and angles [˚] for N-[2-(phenylseleno)ethyl]phthalimide.

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].

We have shown that NaBH₄ can be used as reduction system to generate an organochalcogen anion. This anion reacts in a SN₂ reaction on N-[2-bromoethyl]phthalimide to produce N-[2-(phenylseleno)ethyl]phthalimide (L¹) under mild conditions. These organochalcogen derivatives, L¹, was used to synthesize a metal complex 1, from HgCl₂. L¹ 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, ¹H and ¹³C NMR).

For L¹, 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 L¹. 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

One of the authors (Rupali Rastogi) is grateful to UGC, New Delhi, India for financial assistance. The authors are thankful to the Director, Central Drug Research Institute, Lucknow, India and Chairman CISC, Banaras Hindu University, Varanasi, India for C, H, N analysis and ¹H, ¹³C NMR spectra, respectively. Further, we are also thankful to the Head, School of Studies in Chemistry, Jiwaji University, Gwalior, India for FTIR. Crystallographic studies were supported in part by the Office of Naval Research (ONR) and the Naval Research Laboratory (NRL). RJB would like to acknowledge the NSFMRI program (CHE-0619278) for funds to purchase the X-ray diffractometer.