Reactions of MoO2Cl2 and MoOCl4 with 2-Mercaptopyridine, 4-Phenylimidazole-2-thiol and 6-Mercaptopurine monohydrate

MoO2Cl2/MoOCl4 have been reacted with 4-phenylimidazole-2-thiol/6-mercaptopurine monohydrate/2-mercaptopyridine in acetonitrile solvent in unimolar/bimolar proportions at room temperature. The products thus obtained are: MoOCl3(C9H8N2S),[1]; Mo2O3Cl6(C9H7N2S) (CH3CN)2,[2]; Mo2O3Cl8(C9H7N2S)2(CH3CN)2,[3] and Mo2O4Cl4(C5H4NS-SN4C5),[4]. These products were studied by various techniques: infrared, proton NMR, liquid/gas chromatographymass spectrometry, elemental analyses. Owing to the sensitivity of the products to air and moisture, the reactions and work ups were performed in vacuum line purged with oxygen by flushing dry nitrogen in it. Ions observed in mass spectrum are concurrent with the depicted formulae.


INTRODUCTION
6-Mercaptopurine ring system may be considered as if a pyrimidine ring has been fused to an imidazole ring. Electrons of 6-mercaptopurine are highly delocalized. The ring is susceptible to both electrophilic and nucleophilic attacks. 6-Mercaptopurine 1-2 is used as chemotherapy drugs for treatment of autoimmune diseases and cancer like leukemia, ulcerative colitis and Crohn's disease. Mercaptopurine is sold as purinethol. It is a class of medication known as purine antagonists and works by stopping the growth of cancer cells. Many transition metal complexes of 6-mercaptopurine are reported [3][4] . Some of transition metal complexes of 6-mercaptopurine have higher anticancer activity than that of 6-mercaptopurine [5][6][7][8] . Divalent transition metals coordinate 5,7,9 through S and N atoms of 6-mercaptopurine.

MATERIALS AND METHODS
MoO 2 Cl 2 , MoOCl 4 , 4-phenylimidazole-2-thiol, 6-mercaptopurine monohydrate and 2-mercaptopyridine used were manufactured by Sigma-Aldrich. We used them without any further treatment. Owing to the sensitivity of the products to air and moisture, the reactions and work ups were performed in vacuum line purged with oxygen by flushing dry nitrogen in it. The reactions were carried out for 6-8 h with continuous stirring using pressure stabilised dropping funnel. The products were filtered through filtration unit fitted with G-4 crucible and isolated.
Molybdenum was determined by oxinate 40 gravimetric method. Chlorine was determined by silver chloride 40 gravimetric method. Thermo Finnigan Elemental Analyser was used to determine other elements. Perkin-Elmer 400 FTIR Spectrometer, in the range 4000-400 cm -1 was used to obtain spectra using KBr disks. 1 H-NMR spectra were recorded in solvent DMSO-d 6 using Brucker Avance-II 400 NMR. Liquid Chromatography-Mass spectra were obtained in the range 0-1100 m/z. These facilities were provided by Panjab University, Chandigarh (India).

Preparation of compounds 1-4
Disproportionation/rearrangement might have occurred during the course of reactions. The source of the products is indicated below the products.

AIM of investigation
MoO 2 Cl 2 and MoOCl 4 are known to react with a variety of ligands. The author earlier investigated 31-37 reactions of MoO 2 Cl 2 with various diaminoalkanes, alkanediols, amides, imides, thiols and aromatic azoles.

Mass Spectra (LC-MS) 59
There is formation of [SOCl 2 ] + and [SOCl] + on fragmentation 60 of [4]. Ions observed in mass spectrum are concurrent with the depicted formulae (Tables 8, 9), [2] and [3] do not have any absorption around 2670 cm -1 because there is no S-H group in them. S-H bond does not exist because of presence of υ(C=S) at 1027 cm -1 in both of them. Ions observed in mass spectrum are concurrent with the depicted formulae. S→Mo coordinate bond is likely to be present. Terminal υ(Mo=O) absorbs at 973 cm -1 in [2] and at 970 cm -1 in [3]. S-H peak is missing in 1 H NMR of [2] and [3]. LC-MS supports the predicted formulae. CH 3 CN is present in in [2] and [3] as verified by the presence of its peak in 1 H NMR.
N-H group absorbs at 3383 cm -1 in [4]. Absence of any peak around 2708 cm -1 is because of missing S-H group it. C=S stretching at 1261 cm -1 , 1109 cm -1 are due to C=S group. C-S stretching at 767 cm -1 , 707 cm -1 depict Mo-S bond existence. υ(Mo=O) absorption at 983 cm -1 in [4] suggests presence of terminal Mo=O group it. Fragmentation pattern in LC-MS support the proposed formula.

ACKNOWLEDGEMENT
We thank Panjab University, Chandigarh (India) for providing testing facility.