Lewis-base adducts of group 1B metal(I) compounds. Part 11. Synthesis and crystal structure of adducts of silver(I) bromide with monomethyl-substituted pyridine bases

摘要

Recrystallization of silver(i) bromide from 2-, 3-, and 4-methylpyridine yields the 1 : 2, 1 : 1, and 1 : 1 adducts respectively ; single-crystal X-ray structure determinations are reported at 295 K for the three complexzs. The silver(i) bromide-bis( 2-methylpyridine) adduct consists of a triclinic unit cell of space group P1 , with a = 9.870(8), b = 9.249(9), c = 9.1 85(8) A, a = 109.67(7), j3 = 11 8.38(5), y = 93.23(7)", and Z = 2, containing one centrosymmetric di-p-bromo-bridged binuclear molecular species, [ ( C6H7N)2-AgBr2Ag(C6H7N)2], in the unit cell. R is 0.067 for 1 082 independent 'observed' reflections. Distances include Ag-Br of 2.735(3) and 2.741 (4) A, and Ag-N of 2.32(2) and 2.35(2) A. For the silver(i) bromide-3-methylpyridine adduct, the unit cell is orthorhombic, space group Pccn, with a = 14.71 8(4), b = 14.407(4), c = 7.301 (2) A, and 2 = 8; R = 0.041 for 850 independent 'observed' reflections. The structure is unique among those hitherto reported for coinage metal(i) halide-base adducts, being an infinite polymeric array of dimeric Ag2Br2(base), units linked face-to-face yielding a 'tube' structure, which like all other (MXL) structures may be considered a derivative of the parent metaI(i) halide lattice. For the silver(i) bromide-4-methylpyridine adduct, a monoclinic P2, /n cell is found, with a = 10.286(5), b = 18.066(9), c = 4.390(3) A, P = 104.31 (5)", and four AgBr(base) units in the cell; R = 0.074 for 61 6 'Observed' reflections. The structure is the familiar 'stair polymer' found in a number of other coinage metal(i) halide-base systems.