1,2,3-Dithiazolyl and 1,2,35-Dithiadiazolyl Radicals as Spin-Bearing ...

pellets on a Nicolet 510-FTIR spectrometer at ambient temperature. Elemental analyses
were performed at MHW Laboratories, Phoenix, AZ. Electron paramagnetic resonance
(EPR) spectra were recorded on a Bruker EMX spectrometer.
4-(2′-Pyrimidyl)-1,2,3,5-diselenadiazolium chloride (II-4). A solution of 4,2′-
pyrimidyl-N,N,N′-tris(trimethylsilyl)amidine (1.1072 g, 3.2988 mmol) in 10 mL of
acetonitrile was added to a solution of SeCl 2 [generated in situ from SeCl 4 (0.6588 g,
2.984 mmol) and Se powder (0.2473 g, 3.132 mmol)] in 20 mL of acetonitrile and heated
gently for 1 h. The resulting orange powder was filtered and washed with 3 × 5 mL
portions of acetonitrile and dried in vacuo to afford the title compound used without
further purification, yield: 0.7026 g (69% based on amidine). ν max (KBr)/cm −1 : 3123(w),
3056(w), 3029(w), 3018(w), 2974(w), 2958(w), 1695(w), 1561(s), 1428(m), 1373(m),
1358(m), 1262(w), 1188(m), 1177(m), 1100(w), 992(w), 845(w), 823(w), 781(m),
745(m), 714(w), 680(mw), 661(w), 648(w), 631(m), 596(w), 449(w), 411(w).
4-(2′-Pyrimidyl)-1,2,3,5-diselenadiazolyl (II-1). Solid triphenylantimony (2.0622 g,
5.8408 mmol) was added to a slurry II-4 (3.5902 g, 11.489 mmol) in 100 mL of
acetonitrile and refluxed for 1.5 h. The resulting black powder was filtered and washed
with 3 × 20 mL of acetonitrile and dried in vacuo. Crude yield: 2.9619 g (94% based on
II-4). Crystals suitable for X-ray crystallography were obtained by dynamic vacuum
sublimation (10 −2
Torr) at 110 °C. ν max (KBr)/cm −1 : 3122(w), 3058(w), 3028(w),
3018(w), 2977(w), 2964(w), 1736(w), 1557(s), 1435(w), 1418(s), 1345(m), 1270(w),
1256(w), 1226(w), 1180(m), 1106(w), 989(w), 968(w), 893(w), 877(w), 825(m), 798(w),
101