1. 2-(Imidazol-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol 3-oxide 1-oxyl (1a) was synthesized according to the standard procedure,7 by the reaction of 2,3-bis(hydroxylamino)-2,3-dimethylbutane8 with 4(5)-imidazole carbaldehyde with further oxidation by PbO2. Summary yield 85%; mp 184–185°C; μeff/β=1.73 (295 K); aN=7.70 G. Anal. found: C, 54.0; H, 6.9; N, 24.8. Calcd for C10H15N4O2: C, 53.8; H, 6.8; N, 25.0%.[Cu(1a)2](NO3)2. A solution of Cu(NO3)2 (27 mg, 0.112 mmol) in water (1.5 ml) was added to a solution of 1a (50 mg, 0.195 mmol) in water (4 ml). The dark blue crystals that precipitated 6 h later were filtered off and washed with acetone (2–3 ml). Yield 65%; temp. of decomp. >203°C. Anal. found: C, 38.0; H, 4.9; N, 22.1. Calcd for CuC20H30N10O10: C, 37.9; H, 4.8; N, 22.1.[Cu(3a)2](NO3)2. A solution of Cu(NO3)2 (27 mg, 0.112 mmol) in water (1.5 ml) was added to a solution of 1a (50 mg, 0.195 mmol) in water (4 ml), then a solution of HMTA (7 mg, 0.05 mmol) in water (1 ml) was added. After a day, brown crystals were filtered off and washed with cold water. Yield 55%; temp. of decop. >270°C. Anal. found: C, 40.0; H, 5.4; N, 23.5. Calcd for C20H32CuN10O8: C, 39.8; H, 5.3; N, 23.2.2-(1H-Tetrazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl sodium salt (2c). Typical procedure. A solution of 1c (1.12 g, 3.96 mmol) and HMTA (137 mg, 0.98 mmol) in MeOH (10 ml) was stirred for 10 h at room temperature. Then, PbO2 (2.0 g, 8.4 mmol) was added and the reaction mixture was stirred for 1 h. The precipitate was filtered off and washed with EtOH. The solvent was distilled from the filtrate in vacuo, and the residue was quenched with acetone (5 ml) and filtered off. The product was crystallized from a mixture of MeOH with AcOEt. The initial colorless crystalline precipitate was removed by filtration and the filtrate was kept in a refrigerator for a few days. The resulting orange crystals were filtered off. Yield 520 mg (57%); temp. of decomp. 285°C. Anal. found: C, 41.4; H, 5.2. Calcd for C8H12N6NaO: C, 41.6; H, 5.2%. μeff/β=1.73 (295 K), aN1=9.39 G, aN2=4.54 G.2-(Imidazol-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol 1-oxyl (2a). Yield 57%; mp 174–175°C; μeff/β=1.74 (295 K), aN1=9.35 G, aN2=4.30 G. Anal. found: C, 57.7; H, 7.5. Calcd for C10H15N4O: C, 57.9; H, 7.3.4,4,5,5-Tetramethyl-4,5-dihydro-1H,3′H-[2,4′]biimidazolyl 3-oxide (3a). The reaction time was 3 days. Yield 55%; mp 216–220°C. Anal. found: C, 57.5; H, 8.0; N, 26.9. Calcd for C10H16N4O: C, 57.6; H, 7.7; N, 26.9.
2. Cystal data for 1a·CH3OH: C11H19N4O3, Mw=255.30, monoclinic, space group P21/n, a=10.081(1), b=12.260(2), c=11.614(2) Å, β=110.884(2)°, V=1341.0(3) Å3, Z=4, Dcalcd=1.265 g cm−3, μ=0.094 mm−1, reflections collected/unique=5700/1929 (Rint=0.2027), 231 parameters, Goof=0.932, R1=0.0640, wR2=0.1393 (I>2σ(I)), R1=0.0909, wR2=0.1525 for all data. CCDC reference number 209723. For 2a: C10H15N4O, Mw=255.30, triclinic, space group P1̄, a=13.972(3), b=14.044(3), c=14.484(3) Å, α=111.036(5), β=95.644(5), γ=113.217(5)°, V=2340.7(9) Å3, Z=8, Dcalcd=1.176 g cm−3, μ=0.080 mm−1, reflections collected/unique=9993/6626 (Rint=0.0851), 752 parameters, Goof=0.763, R1=0.0642, wR2=0.1039 (I>2σ(I)), R1=0.2088, wR2=0.1447 for all data. CCDC reference number 209719. For [Cu(1a)2](NO3)2·3H2O: C20H36CuN10O13, Mw=688.13, orthorhombic, space group Pccn, a=13.353(3), b=25.864(6), c=8.675(2) Å, V=2996.3(12) Å3, Z=4, Dcalcd=1.525 g cm−3, μ=0.808 mm−1, reflections collected/unique=11733/2149 (Rint=0.0758), 274 parameters, Goof=0.761, R1=0.0394, wR2=0.1048 (I>2σ(I)), R1=0.0514, wR2=0.1141 for all data. CCDC reference number 209722. For [Cu(3a)2](NO3)2: C20H32CuN10O8, Mw=604.10, monoclinic, space group P21/n, (No. 14), a=7.301(1), b=23.701(4), c=8.002(1) Å, β=105.295(3)°, V=1335.7(3) Å3, Z=2, Dcalcd=1.502 g cm−3, μ=0.881 mm−1, 5676 reflections measured, 1920 unique (Rint=0.1116), 1920 observed (I>2σ(I)), 243 parameters, Goof=0.827, R1=0.0462, wR2=0.1167 (I>2σ(I)), R1=0.0636, wR2=0.1324 for all data. CCDC reference number 209718. For 2c: C8H12N6NaO, Mw=231.23, monoclinic, space group P21/c, a=10.354(2), b=8.962(1), c=12.915(2) Å, β=113.630(1)°, V=1097.9(3) Å3, Z=4, Dcalcd=1.399 g cm−3, μ=0.133 mm−1, reflections collected/unique=3059/1564 (Rint=0.1199), 194 parameters, Goof=0.870, R1=0.0619, wR2=0.1114 (I>2σ(I)), R1=0.1155, wR2=0.1287 for all data. CCDC reference number 209720. For 3a: C10H16N4O, Mw=208.27, orthorhombic, space group P212121, a=7.5254(9), b=12.096(2), c=12.488(2) Å, V=1136.7(2) Å3, Z=4, Dcalcd=1.217 g cm−3, μ=0.083 mm−1, reflections collected/unique=4924/1638 (Rint=0.1301), 201 parameters, Goof=1.009, R1=0.0391, wR2=0.0989 (I>2σ(I)), R1=0.0404, wR2=0.1002 for all data. CCDC reference number 209721. The reflection data were collected on a Smart Apex Bruker AXS, Mo-Kα radiation (λ=0.71073 Å), all structures were solved using standard direct method techniques, and refined using full-matrix least-squares based on F2. Hydrogen atoms were localized in Δρ synthesis and refined isotropically with anisotropic non-hydrogen atoms.
3. Periodic Tiling of Pentagons: The First Example of a Two-Dimensional ( )-net
4. Synthetic Chemistry of Stable Nitroxides;Volodarsky,1994
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