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

Abstract

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 complexes. The silver(I) bromide–bis(2-methylpyridine) adduct consists of a triclinic unit cell of space group P, with a= 9.870(8), b= 9.249(9), c= 9.185(8)Å, α= 109.67(7), β= 118.38(5), γ= 93.23(7)°, and Z= 2, containing one centrosymmetric di-µ-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)Å, and Ag–N of 2.32(2) and 2.35(2)Å. For the silver(I) bromide–3-methylpyridine adduct, the unit cell is orthorhombic, space group Pccn, with a= 14.718(4), b= 14.407(4), c= 7.301(2)Å, and Z= 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)2 units linked face-to-face yielding a ‘tube’ structure, which like all other (MXL) structures may be considered a derivative of the parent metal(I) halide lattice. For the silver(I) bromide–4-methylpyridine adduct, a monoclinic P21/n cell is found, with a= 10.286(5), b= 18.066(9), c= 4.390(3)Å, β 104.31(5)°, and four AgBr(base) units in the cell; R= 0.074 for 616 ‘observed’ reflections. The structure is the familiar ‘stair polymer’ found in a number of other coinage metal(I) halide–base systems.