Crystal Structures of the 1:1 Adducts of N,N,N′,N′- Tetramethyl-o-phenylenediamine with Zinc(II) Bromide and Mercury(II) Bromide and Iodide

Abstract

The 1:1 adducts of o-Me₂N.C₆H₄.NMe₂ (≡ L″) with ZnI₂, HgBr₂ and HgI₂ are isomorphous and their crystal structures have been established by single-crystal X-ray diffraction methods, being refined to residuals of 0.045, 0.050, 0.035, for 1759, 1617, 1911 'observed' reflections respectively. Crystals are monoclinic P2₁/c,Z = 4, with a ~ 8.5, b ~ 21, c ~ 8 Ǻ, β ~ 95°. In L″ZnI₂, {Zn-I} is 2.53₈, {Zn-N} 2.09 Ǻ, with I-Zn-I 115.36(6), N-Zn-N 84.6(3), and I-Zn-N 108.3(2)-118.3(2)°. In L″HgBr₂, (Hg-Br) is 2.52₃, {Hg-N} 2.42 Ǻ, with Br-Hg-Br 123.04(8), N-Hg-N 73.2(4) and Br-Hg-N 98.9(3)-131.2(3)°. In L″HgI₂, {Hg-I} is 2.66₁, {Hg-N} 2.44 Ǻ, with I-Hg-I 128.92 (3), N-Hg-N 72.8(3), and I-Hg-N 101.8(2)- 122.9(2). X-Hg-X angles are unexpectedly small and this is attributed to incipient dimer formation through an inversion centre, this tendency being greatest in (2) where the Hg…Br approach is 3.456(3) Ǻ and the immediate HgBr₂N environment of the mercury is trigonal planar.