Lewis-Base Adducts of Lead(II) Compounds. XIV. Synthetic and Structural Studies of Some 2:1 Adducts of 2,2'-Bipyridine With Lead(II) Oxoanion Salts

Abstract

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 )₂Pb(NO₃)₂]₂ is triclinic, Pī , a 14.609(6), b 9.400(4), c 8.396(4) Ǻ, α 71.10(3), β 83.53(3), γ 81.72(3)°, Z = 1 dimer; R was 0.037 for N_o = 3001 independent, 'observed' (I > 3σ(I)) reflections. [( bpy )₂Pb(ClO₄)₂] is monoclinic, P2₁/c, a 9.8806(6), b 12.198(6), c 19.924(2) Ǻ, β 106.80(1)°, Z = 4, R 0.040 for N_o 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 )₂PbX(ClO₄), X = acetate ('ac'), chloride. [( bpy )₂Pb(ac)(ClO₄)] is triclinic, Pī , a 15.910(6), b 9.067(5), c 8.588(3) Ǻ, α 102.91(4), β 93.64(3), γ 103.41(4)°, Z = 2, R 0.039 for N_o 5283. [( bpy )₂PbCl(ClO₄)₂ is monoclinic, P 2₁/c, a 12.923(2), b 8.759(2), c 19.650(2) Ǻ, β 94.776(9)°, Z = 2 dimers (R 0.037 for N_o 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 μ-chloride ions linking the two lead atoms which have seven-coordinate PbN₄(μ- Cl )₂O lead environments, the perchlorate species being O-unidentate.