Organoselenium compounds containing pyrazole or phenylthiazole groups: Synthesis, structure, tin(IV) complexes and antiproliferative activity.

The diorganodiselenides (pzCH2CH2)2Se2 (<bold>1</bold>) and (PhtzCH2)2Se2 (<bold>2</bold>) were prepared by reacting Na2Se2 with 1‐(2‐bromoethyl)‐1H‐pyrazole and 4‐(chloromethyl)‐2‐phenylthiazole, respectively, while the reactions between 1‐(2‐bromoethyl)‐1H‐pyrazole or 4‐(chloromethyl)‐2‐phenylthiazole and the lithium organoselenolates [2‐(Et2NCH2)C6H4]SeLi and [2‐{O(CH2CH2)2NCH2}C6H4]SeLi in a 1:1 molar ratio resulted in the heteroleptic diorganoselenium(II) compounds [2‐(Et2NCH2)C6H4](R)Se (R = pzCH2CH2 (<bold>3</bold>) or PhtzCH2 (<bold>5</bold>)) and [2‐{O(CH2CH2)2NCH2}C6H4](R)Se (R = pzCH2CH2 (<bold>4</bold>) or PhtzCH2 (<bold>6</bold>)). The diorganotin(IV) bis(organoselenolato) derivatives of type R2Sn(SeCH2CH2pz)2 (R = 2‐(Me2NCH2)C6H4 (<bold>7</bold>) or Me (<bold>8</bold>)) were obtained by reacting (pzCH2CH2)SeNa with the appropriate diorganotin(IV)dichloride in a 2:1 molar ratio. All compounds were investigated using NMR spectroscopy (1H, 13C, 77Se, 119Sn as appropriate) and ESI+ mass spectrometry. The molecular structures of <bold>2</bold> and <bold>6</bold> were determined using single‐crystal X‐ray diffraction. The formation of a 10–Se–3 hypercoordinated species was evidenced for <bold>6</bold> in the solid state, as a consequence of the <italic>C,N</italic> coordination behaviour of the 2‐{O(CH2CH2)2NCH2}C6H4 group. Compounds <bold>1</bold>, <bold>7</bold> and <bold>8</bold> were investigated for their antiproliferative activity towards the mouse colon carcinoma C26 cell line with the preliminary results showing a better activity than 5‐fluorouracil. [ABSTRACT FROM AUTHOR]