Structural and Infrared Spectroscopic Studies of Some Adducts of Divalent Metal Dihalides ( MX 2 , M = Zn, Cd; X = CI, Br, I) with Variously Hindered Monodentate Nitrogen (Pyridine) Base Ligands (L = Pyridine, 2‐Methylpyridine, and Quinoline) of 1:2 Stoichiometry

Single crystal X‐ray structure determinations are described for a number of adducts of 1:2 MX 2 :L stoichiometry, [ M = divalent metal (Zn, Cd); X = halide (Cl, Br, I), L = (variously hindered) monodentate nitrogen (pyridine) base: py = pyridine, 2‐mpy = 2‐methylpyridine, quin = quinoline]: [(2‐mpy) 2 Zn X 2 ] ( X = Cl, Br) (isotypic, triclinic P $\bar{1}$ , a ≈ 7.9 6 , b ≈ 8.7, c ≈ 11.4 Å, α ≈ 86, β ≈ 79.3, γ ≈ 67°, Z = 2), [(2‐mpy) 2 ZnI 2 ], [(quin) 2 Zn X 2 ] ( X = Br) (isotypic with the previously determined chloride, X = Cl, triclinic, P $\bar{1}$ , a ≈ 8.7, b ≈ 9.6, c ≈ 11.1 Å, α ≈ 81, β ≈ 73, γ ≈ 72°, Z = 2); [(quin) 2 ZnI 2 ]; [(2‐mpy) 2 Cd X 2 ], X = Br {isotypic with [(2‐mpy) 2 Zn X 2 ], X = Cl, Br (above)}, X = I {isotypic with [(2‐mpy) 2 ZnI 2 ] (above)}; [(quin) 2 CdI 2 ]. A single molecule, with a four‐coordinate quasi ‐tetrahedral metal atom, N 2 MX 2 , comprises the asymmetric unit of the structure in each of these. A one‐dimensional polymer is found for [(quin) 2 Cd(μ‐Cl) 2 ] (∞‖∞) , similar to those recorded previously for Cd X 2 :py (1:2) ( X = Cl, Br, I), the cadmium atom here lying on a 2‐axis in tetragonal space group P $\bar{4}$ 2 1 c , and the quin ligands coordinating trans in a six‐coordinate array about the cadmium, with successive cadmium atoms being linked by pairs of bridging chlorines. Adducts of MX 2 :L (1:1) stoichiometry, defined for M = Cd: [(2,4,6‐trimethylpyridine)Cd(μ‐I) 2 ] (∞‖∞) and [(quin)Cd(μ‐Br) 2 ] (∞‖∞) , are both infinite one‐dimensional polymers … (μ‐ X ) 2 Cd(L)(μ‐ X ) 2 Cd(L) … , with five‐coordinate trigonal bipyramidal cadmium atoms, the nitrogen donors being equatorial in the coordination spheres. The far‐IR spectra of [L 2 MX 2 ] (L = py, 2‐mpy, quin; M = Zn, Cd; X = Cl, Br, I) are assigned and discussed in relation to the structures of the complexes.