Coordination dimers constructed from metal(II) halides and the organic ligand 1,2-dimethoxy- 4,5-bis(2-pyridylethynyl)benzene

A series of new coordination compounds has been synthesized using the organic ligand 1,2-dimethoxy-4,5-bis(2-pyridylethynyl)benzene (dmpeb). The compounds all form dimers consisting of two metal cations bridged by two ligand molecules. Charge balance is provided by halide ligands, and the four-coordinate metal centers are distorted from the ideal tetrahedral environment. [CoCl2(dmpeb)]2 (1) crystallizes in the monoclinic space group P21/n with a = 8.5272(6) Å, b = 18.3653(13) Å, c = 13.3493(9) Å, β = 103.574(2)∘, V = 2032.2(2) Å3, Z = 2. [ZnCl2(dmpeb)]2 (2) is isostructural to 1 and has the cell parameters a = 8.5495(4) Å, b = 18.4049(8) Å, c = 13.3692(6) Å, β = 103.4460(10)∘, V = 2046.01(16) Å3, Z = 2. [ZnBr2(dmpeb)]2 (3) is also isostructural to 1 with a = 8.7882(5) Å, b = 18.7260(12) Å, c = 13.3857(8) Å, β = 102.5990(10)∘, V = 2149.8(2) Å3, Z = 2. Additionally, the compounds [ZnI2(dmpeb)]2 (4, cell parameters: a = 8.9650(5) Å, b = 19.1251(10) Å, c = 13.4160(7) Å, β = 101.1660(10)∘, V = 2256.7(2) Å3, Z = 2), [HgCl2(dmpeb)]2 (5, cell parameters: a = 8.8457(7) Å, b = 18.4030(15) Å, c = 13.3711(11) Å, β = 104.246(2)∘, V = 2109.7(3) Å3, Z = 2), and [HgBr2(dmpeb)]2 (6, cell parameters: a = 9.0576(5) Å, b = 18.8634(11) Å, c = 13.4535(8) Å, β = 102.9780(10)∘, V = 2239.9(2) Å3, Z = 2) are also isostructural to 1. A seventh dimeric compound, [HgI2(dmpeb)]2, not isostructural to the others was also characterized by X-ray crystallography. [HgI2(dmpeb)]2 (7) crystallizes in the triclinic space group P-1 with a = 8.8028(5) Å, b = 12.0990(7) Å, c = 12.4082(7) Å, α = 109.7240(10)∘, β = 107.3680(10)∘, γ = 93.0880(10)∘, V = 1169.57(12) Å3, Z = 1.