Coordination Polymers of Copper(I) Halides

A total of 21 complexes of CuX (X = Cl, Br, I) with bridging ligand (B = 4,4‘-dipyridyl (Bpy), pyrazine (Pyz),
quinoxaline (Quin), phenazine (Phz), 1,4-diazabicyclo[2.2.2]octane (DABCO), and hexamethylenetetramine
(HMTA)) have been synthesized. The products show two stoichiometries:  [CuXB] (type 1) and [(CuX)2B] (type
2). Both types can be obtained for B = Bpy, depending on the conditions of preparation. In these cases, the type
2 stoichiometry is the kinetic product. Type 2 complexes only are found for B = Pyz (X = I), Quin, Phz, DABCO,
and HMTA. Type 1 complexes form for Pyz (X = Cl, Br). Thermogravimetic analyses of the complexes reveal
the general decomposition trend:  1 → 2 → [(CuX)2B1/2] → CuX. The X-ray crystal structure of [CuBr(Pyz)]
(type 1) features copper atoms bridged by Br and Pyz, forming 2D sheets of fused rectangular Cu4Br2(Pyz)2
units. The X-ray structure of [(CuI)2(Quin)] (type 2) shows 2D layers composed of [Cu2I2]∞ “stair step” chains
which are cross-linked by Quin ligands. A total of 16 complexes of CuXL (L = P(OPh)3) with bridging ligand
(B = those above and 1,4-dimethylpiperazine (DMP)) have also been prepared. All of these products, except
those of HMTA, are of type 3 formulation, [(CuXL)2B]. The HMTA products have the formula [CuX(HMTA)],
type 4. Thermal decomposition of the type 3 and 4 complexes occurs with initial loss of B, L, or both. The X-ray
structures of [(CuBrL)2(Bpy)] and [(CuBrL)2(Pyz)] (type 3) reveal 1D chains formed from rhomboidal (LCu)2Br2
units linked by the B ligand. The type 4 structure of [CuBrL(HMTA)] is shown by X-ray to be a simple halide-bridged dimer.