Lewis-base adducts of lead(II) compounds .14. Synthetic and structural studies of some 2:1 adducts of 2,2'-bipyridine with lead(II) oxoanion salts

Syntheses and room-temperature single-crystal X-ray structure determinations are recorded for 2:1 adducts of the N,N'-bidentate aromatic base 2,2'-bipyridine ('bpy') with lead(II) nitrate and perchlorate. [(bpy)(2)Pb(NO3)(2)](2) is triclinic, <P(1)over bar>, a 14.609(6), b 9.400(4), c 8.396(4) Angstrom, alpha 71.10(3), beta 83.53(3), gamma 81.72(3)degrees, Z = 1 dimer; R was 0.037 for N-0 = 3001 independent, 'observed' (I > 3 sigma(I)) reflections. [(bpy)(2)Pb(ClO4)(2)] is monoclinic, P2(1)/c, a 9.8806(6), b 12.198(6), c 19.924(2) Angstrom, beta 106.80(1)degrees, Z = 4, R 0.040 for N-0 4456. Unlike the two 1,10-phenanthroline ('phen') systems which are mononuclear with eight-coordinate PbN4O4 environments incorporating a pair of O,O'-bidentate anions, the bpy systems are centrosymmetric dimers; in each case the coordination environment incorporates a pair of N,N'-bidentate aromatic bases and an O,O'-bidentate anion, but the other anion is not only O,O'-bidentate, but also bridges by a third oxygen atom to the other lead atom so that it is nine-coordinate PbN4O5. Syntheses and room-temperature single-crystal X-ray structure determinations are also recorded for a pair of 2:1 adducts of 2,2'-bipyridine with lead(II) salts of mixed anion stoichiometry, viz. (bpy)(2)PbX(ClO4), X = acetate ('ac'), chloride. [(bpy)(2)Pb(ac)(ClO4)] is triclinic, <P(1)over bar>, a 15.910(6), b 9.067(5), c 8.588(3) Angstrom, alpha 102.91(4), beta 93.64(3), gamma 103.41(4)degrees, Z = 2, R 0.039 for N-0 5283. [(bpy)(2)PbCl(ClO4)](2) is monoclinic, P2(1)/c, a 12.923(2), b 8.759(2): c 19.650(2) Angstrom, beta 94.776(9)degrees, Z = 2 dimers (R 0.037 for N-0 4433). Like the 1:2 oxoanion/phen adducts, the acetate is a discrete molecular species with an eight-coordinate PbN4O4 lead environment, the oxygen array comprising a pair of O,O'-bidentate perchlorate and acetate ligands. The chloride adduct, however, is like the 1:2 oxoanion/bpy adducts, being centrosymmetric binuclear, a pair of mu-chloride ions linking the two lead atoms which have seven-coordinate PbN4(mu-Cl)(2)O lead environments, the perchlorate species being O-unidentate.