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 No 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 No 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 No 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 No 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 No 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 No 2583].