LEWIS-BASE ADDUCTS OF LEAD(II) COMPOUNDS .12. SYNTHETIC, SPECTROSCOPIC AND STRUCTURAL STUDIES OF SOME 1 1 ADDUCTS OF LEAD(II) (PSEUDO-)HALIDES WITH AROMATIC BIDENTATE LIGANDS/

Syntheses and room-temperature single-crystal X-ray structure determin ations are recorded for some 1:1 adducts of lead(II) (pseudo-)halides with 1,10-phenanthroline ('phen') and 2,2'-bipyridine ('bpy'). [(phen) PbX(2)]((infinity/infinity)), X = Cl, Br, I, have been refined in a co mmon monoclinic C2/c setting, a approximate to 16 2, b approximate to 10.6, c approximate to 8.2(5) Angstrom, beta approximate to 105 degree s, Z = 4 f.u.; (conventional R on /F/ 0.034, 0.046, 0.043 for N-0 = 16 94, 1626, 1387 independent, 'observed' (I > 3 sigma(I)) reflections re spectively); [(bpy)PbI2]((infinity/infinity)) is isomorphous with simi lar cell dimensions (R 0.035 for N-0 1263), but, in its chloride count erpart, the symmetry is degraded to P2(1)/c, a 15.336(5), b 9.476(5), c 8.191(3) Angstrom, beta 92.81(3)degrees, Z = 4 (R 0.041 for N-0 2849 ). In the C2/c model the lead atoms are disposed on crystallographic 2 axes, as also are the associated N,N'-bidentate ligands, with the six -coordinate (cis-N-2)Pb(mu-X)(4) environments linked in an infinite .. . (mu-X)(2)Pb(mu-X)(2)Pb ... one-dimensional polymeric chain by bridgi ng halogen atoms. A somewhat similar, albeit more complex, array is fo und in [(bpy)Pb(SCN)(2)]((infinity/infinity)), monoclinic, C2/c, a 17. 655(6): b 12.027(3), c 6.794(1) Angstrom, beta 107.03(2)degrees, Z = 4 (R 0.028 for N-0 1064), isomorphous with its previously studied phen analogue, in which a web of bridging SCN units is found. Stacks of suc cessive strands up b have interleaving arrays of ligands and (pseudo-) halide atoms. The far-infrared spectrum of [(phen)PbCl2] shows four st rong, broad bands at 152, 144, 116 and 96 cm(-1) which are assigned as v(Pb-Cl) The corresponding bands in the bromo and iodo complexes are shifted to below 100 cm(-1), revealing sharper bands at about 120 and 150 cm(-1) which are assigned to v(Pb-N) modes. The low wavenumbers of the v(Pb-X) bands are indicative of weak Pb-X bonding. The far-infrar ed spectrum of the previously reported [(phen)Pb(NCS)(2)] complex is s imilar to that of the chloro complex, consistent with its similarity i n structure.