Lewis-base adducts of lead(II) compounds .18. Synthetic and structural studies of some 1:1 and 2:1 adducts of 2,4,6-tris (2-pyridyl)-1,3,5-triazine with lead(II) nitrate

Adducts of lead(II) nitrate with 2,4,6-tris(2-pyridyl)-1,3,5-triazine ('trz') have been synthesized and structurally characterized by room-temperature single-crystal X-ray studies, for 1 : 1 and 1 : 2 stoichiometry. Crystals of [(trz)Pb(NO3)(2)]((infinity\infinity)) are monoclinic, P2(1)/c, a 10.531(1), b 12.856(2), c 16.874(3) Angstrom, beta 102.83(1)degrees, Z = 4 f.u.; R was 0.027 for N-o = 2773 'observed' (I > 3 sigma(I)) reflections. The complex is an infinite polymer; the plane of the tridentate trz ligand lies normal to the polymer axis (Pb-N(central; distal) 2.523(5); 2.594(5), 2.568(5) Angstrom) with unsymmetrically bidentate nitrate groups to either side (Pb-O 2.598(6), 2.928(7); 2.556(6), 2.911(7) Angstrom). The third oxygen of each nitrate group bridges to the next lead atom in the polymer chain (Pb-O 3.008(5), 3.083(6) Angstrom). [(trz)(2)Pb(NO3)(2)] is monoclinic, C2/c, a 15.723(5), b 10.034(2), c 24.379(15) Angstrom, beta 106.84(4)degrees, Z = 4 f.u.; R was 0.038 for N-o 3030. The compound is a methanol monosolvate. The complex species is mononuclear, with the lead atom located on a crystallographic 2 axis and 10-coordinated by pairs of symmetry-related tridentate trz (Pb-n(central; distal) 2.779(4); 2.800(5), 2.818(5) Angstrom) and bidentate nitrate ligands (Pb-O 2.796(6), 2.689(5) Angstrom). A hexahydrate has also been obtained (triclinic, <P(1)over bar> a 23.580(9), b 10.147(4), c 9.762(4) Angstrom, alpha 113.14(3), beta 92.11(3), gamma 101.60(3)degrees, Z = 2 f.u; R 0.041 for N-o 5633); although metal-ligand distances are similar to those found in the methanol solvate, and quasi-2 symmetry is retained, a very different stereochemistry is evident in respect of the relative dispositions of the ligands about the (quasi)-2 axis, involving a substantial twist of the two nitrate ligands relative to the triazines, and a flattening of the latter. The coordination polyhedron is different in the two 1:2 adducts. In the methanol solvate the stereochemistry is pentagonal antiprismatic whereas in the hexahydrate it is bicapped square antiprismatic.