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-t emperature single-crystal X-ray studies, for 1 : 1 and 1 : 2 stoichiom etry. Crystals of [(trz)Pb(NO3)(2)]((infinity\infinity)) are monoclini c, P2(1)/c, a 10.531(1), b 12.856(2), c 16.874(3) Angstrom, beta 102.8 3(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 o f the tridentate trz ligand lies normal to the polymer axis (Pb-N(cent ral; distal) 2.523(5); 2.594(5), 2.568(5) Angstrom) with unsymmetrical ly 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 br idges 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 cryst allographic 2 axis and 10-coordinated by pairs of symmetry-related tri dentate trz (Pb-n(central; distal) 2.779(4); 2.800(5), 2.818(5) Angstr om) 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 23.5 80(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 solv ate, and quasi-2 symmetry is retained, a very different stereochemistr y is evident in respect of the relative dispositions of the ligands ab out the (quasi)-2 axis, involving a substantial twist of the two nitra te ligands relative to the triazines, and a flattening of the latter. The coordination polyhedron is different in the two 1:2 adducts. In th e methanol solvate the stereochemistry is pentagonal antiprismatic whe reas in the hexahydrate it is bicapped square antiprismatic.