Lewis-Base Adducts of Lead(II) Compounds. VIII. Synthetic and Structural Studies of Some Adducts of Linear Polyamines With Lead(II) Bromide

Abstract

Syntheses and room-temperature single-crystal X-ray structure determinations are recorded for adducts of lead(II) bromide with some linear polyamines. Adducts with ethane-1,2-diamine ('en') and propane- 1,2-diamine (' pn ') are of 2:1 and 1:1 stoichiometry respectively. [(en)₂PbBr₂]_(∞|∞) is monoclinic, C2/c, a 13,076(4), b 7.586(2),c 13.248(4) Ǻ, β 117.88(2)°, Z = 4 f.u .; R was 0.029 for N_o = 1832 'observed' (I > 3σ(I)) reflections (a redetermination ). [( pn )PbBr₂]_(∞|∞) is orthorhombic, Pbca , a 23.457(3), b 9.567(2), c 7.714(3) Ǻ, Z = 8; R 0.051 for N_o 1297. [(en)₂PbBr₂](∞|∞) is a single stranded linear polymer parallel to c; the lead atom, lying on a crystallographic twofold axis, is six-coordinate PbN₄Br₂, with the bromine atoms cis in the coordination sphere and lying opposed to a bidentate en ligand. The trans sites are linked into a chain by bridging en ligands . [( pn )PbBr₂](∞|∞) is a more complex two-dimensional polymer; the pn is bidentate , but the lead atoms are now eight coordinate with doubly and quadruply bridging bromines linking them into the polymeric sheet. The adduct with '323tet' (4,7-diazadecane 1,10-diamine) is of a novel (323tet)₂(PbBr₂)₃ stoichiometry , best represented (simplistically) as {[ Pb (323tet)]₂[PbBr₆]}(∞|∞); crystals are triclinic, Pī , a 11.892(4), b 9.306(3), c 9.016(6) Ǻ, α 60.74(4), β 86.04(4), γ 74.43(3)°, Z = 1 f.u ., with R 0.061 for N_o 2071. About one lead atom type, the ligand is quadridentate , lying on one face of the coordination sphere; the region opposite is occupied by four triply bridging bromine atoms from the [PbBr₆] anionic units (which contain quasi-octahedral, centrosymmetric lead. with a pair of trans-bromine atoms terminal and the others bridging) linking the array into a two dimensional polymer.