Lewis-Base Adducts of Lead(II) Compounds. IX. Synthetic and Structural Studies of Some 1:1 Adducts of 'cyclam' and Its Hexamethylated Derivative 'tet-b' With Lead(II) Oxoanion Salts

Abstract

Syntheses and room-temperature single-crystal X-ray structure determinations are recorded for 1 : 1 adducts of (1,4,8,11-tetraazacyclotetradecane) ('cyclam') with lead(II) perchlorate and (7R*,14R*)-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane ('tet -b') with lead(II) nitrate, perchlorate and acetate ('ac'). [( cyclam ) Pb (ClO₄)₂] is orthorhombic, Pb2₁a, a 16.024(7), b 13.595(4), c 8.6810(5) Ǻ, Z = 4 f.u .; R was 0.055 for N_o 1318 independent 'observed' (I > 3σ(I)) reflections. [( tet -b) Pb (NO₃)₂]₂ is monoclinic. P 2₁/a, a 16.15(2), b 14.550(6), c 19.775(2) Ǻ, β 90.86(5)°, Z = 4 dimers ; R 0.074 for N_o 3184. [( tet -b) Pb (ClO₄)₂]₂.H₂O is monoclinic, P 2₁/c, a 13.663(9), b 9.031(3). c 20.61(1) Ǻ, β 100.40(3)°, Z = 4 f.u .; R 0.044 for N_o 2857. [( tet -b) Pb (ac)₂].2H₂O is triclinic, Pī , a 13.138(5), b 10.924(4), c 10.518(3) Ǻ, α 115.48(3), β 91.95(2), γ 102.38(2)°, Z = 2 f.u .; R 0.031 for N_o 6485. In all complexes, the macrocycle-N₄ ligand occupies one 'side' of the coordination sphere of the lead atom, with anionic oxygens opposed; the cyclam/perchlorate complex is, like the nitrate, mononuclear with seven-coordinate (N₄)PbO₃ with a bidentate O,O'- and a unidentate O- perchlorate . In the tet-b acetate, the anionic oxygen atoms are surprisingly sparse, comprising simply a bidentate acetate in a mononuclear (N₄)PbO₂ environment with the other (lattice) acetate bonded to the macrocycle axial NH hydrogens . The nitrate and perchlorate complexes involve bridging anions: in the nitrate. a central centrosymmetric PbO₂Pb array is found, the lead atoms being bridged by one oxygen of a bidentate nitrate, the other nitrate being unidentate and the coordination sphere (N₄)PbO₄: in the perchlorate , again a centrosymmetric dimer is found, the lead atoms being linked by O,O'-bridging perchlorates (again with (N₄)PbO₂ coordination environments), the complex being essentially [( tet -b) Pb (OClO₂O)₂Pb( tet -b)](ClO₄)₂H₂O. The structure of [cyclamH₄]⁴⁺ (NO₃-)₄.2H₂O is also recorded [triclinic, Pī , a 8.626(2), b 8.549(1), c 8.400(2) Ǻ, α 80.60(2), β 76.62(2), γ 65.06(1)°, Z = 1; R 0.044 for N_o 1539], together with that of the diprotonated hexamethyl derivative [tet-bH₂]²⁺(ClO₄-)₂.CH₃OH [monoclinic, P2₁/c, a 11.296(3), b 8.834(8), c 26.22(1) Ǻ, β 99.05(3)°, Z = 4 f.u .; R 0.063 for N_o 2583].