Brook D J, Fornell S, Stevens J E, Noll B, Koch T H, Eisfeld W
University of Detroit Mercy, Michigan 48219-0900, USA.
Inorg Chem. 2000 Feb 7;39(3):562-7. doi: 10.1021/ic9903883.
Ferricyanide oxidation of 1,4,5,6-tetrahydro-2,4-dimethyl-6-(2'-pyridyl)-1,2,4,5-tetrazin-3(2H)-one (pvdH3) produces the stable chelating free radical 1,5-dimethyl-3-(2'-pyridyl)-6-oxoverdazyl (pvd) as an orange solid. Combination of group 12 metal halides with the ligand pvdH3 in acetonitrile results in precipitation of metal complexes. The mercuric chloride complex crystallizes in the monoclinic space group P2(1/c) with unit cell dimensions a = 8.5768(8) A, b = 19.1718(17) A, c = 8.5956(8) A, beta = 90.405 degrees, and V = 1413.4(2) A3. The mercuric ion is tricoordinate with a distorted trigonal planar geometry. Cadmium iodide and zinc chloride induce ring opening of the tetrazine resulting in pentacoordinate complexes of a hydrazone ligand. The cadmium iodide complex crystallizes in the triclinic space group P1 with cell dimensions a = 7.7184(8) A, b = 8.0240(9) A, c = 13.348(2) A, alpha = 97.876(4) degrees, beta = 95.594(6) degrees, gamma = 107.304(6) degrees, and V = 773.40(21) A3. Oxidation of all three metal complexes produces verdazyl radicals. Metal coordination is indicated by small changes in the EPR spectrum and by changes in the UV-visible spectrum, in particular the changes in the position of bands in the visible region. The metal halide-pvd complexes can also be synthesized by direct combination of metal halides with the free radical.
1,4,5,6 - 四氢 - 2,4 - 二甲基 - 6 - (2'-吡啶基)-1,2,4,5 - 四嗪 - 3(2H)-酮（pvdH3）的铁氰化物氧化反应生成稳定的螯合自由基1,5 - 二甲基 - 3 - (2'-吡啶基)-6 - 氧代过氮自由基（pvd），呈橙色固体。12族金属卤化物与配体pvdH3在乙腈中反应会生成金属配合物沉淀。氯化汞配合物在单斜空间群P2(1/c)中结晶，晶胞参数为a = 8.5768(8) Å，b = 19.1718(17) Å，c = 8.5956(8) Å，β = 90.405°，V = 1413.4(2) ų。汞离子为三配位，具有扭曲的三角平面几何构型。碘化镉和氯化锌会引发四嗪环开环，生成腙配体的五配位配合物。碘化镉配合物在三斜空间群P1中结晶，晶胞参数为a = 7.7184(8) Å，b = 8.0240(9) Å，c = 13.348(2) Å，α = 97.876(4)°，β = 95.594(6)°，γ = 107.304(6)°，V = 773.40(21) ų。所有三种金属配合物的氧化反应都会生成过氮自由基。EPR谱中的微小变化以及紫外 - 可见光谱中的变化，特别是可见区域谱带位置的变化，都表明了金属配位情况。金属卤化物 - pvd配合物也可以通过金属卤化物与自由基直接反应合成。
