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Reaction Of Cu(ClO4)2 with 2,3-dimethylpyrazine (2,3-dmpz) in aqueous solution yields the bright yellow, air-stable, crystalline complex Cu2(2,3-dmpz)3(ClO4)2 (1) in 40% yield. The single-crystal X-ray structure reveals a two-dimensional polymeric lattice of tricoordinate copper(I) atoms bridged by 2,3-dimethylpyrazine ligands.

The crystal structures of two hydrated copper(II) chloride salts are reported: N,N'-dimethylpiperazinium bis(aquotrichlorocuprate(II)), C 6 H 20 N 2 O 2 Cu 2 Cl 6 , monoclinic, P2 1 /n, a=6.714 (2) A, b=6.215 (2) A, c=19.545 (6) A, β=92.24 (6)°, Z=2, and R=0.041, and 2-aminopyrimidinium aquotrichlorocuprate(II), C 4 H 8 N 3 OCuCl 3 , monoclinic, Cc, a=3.9025 (6) A, b=13.788 (3) A, c=16.826 (3) A, β=93.99 (1)°, Z=4, and R=0.030. In addition, the crystal parameters of the anhydrous analogue of the latter, bis(2-aminopyrimidinium) hexachlorodicuprate(II), C 8 H 12 N 6 Cu 2 Cl 6 are triclinic, a=3.902 (1) A, b=10.850 (3) A, c=11.129 (3) A, α=62.82 (2)°, β=84.84 (3)°, γ=82.69 (2)°, Z=1, and R=0.0252

The reaction of 4,4'-dimethyl-2,2-bipyridine (henceforth dmbp) with copper(I) and/or copper(II) bromide under a wide variety of conditions has led to the isolation of 10 different crystalline materials. These include one Cu(I) salt, [Cu(dmbp)(2)]Br (a distorted tetrahedral Cu species and a lattice Br(-) ion); two mixed valence Cu(I,II) compounds, [Cu(dmbp)(2)Br][CuBr(2)] (discrete 5-coordinated Cu(II) and linear Cu(I) species) and Cu(dmbp)(2)BrCu(2)Br(3) (linked 5-coordinate Cu(II) and trigonal planar Cu(I) species); and seven Cu(II) compounds, (dmbp)CuBr(2) (stacked planar monomers), [(dmbp)CuBr(2)](2)(five coordinate bibridged dimers), (dmbp)Cu(2)Br(4) (stacked planar bibridged dimers), (dmbp)CuBr(2)(DMSO) (five coordinate monomers), [Cu(dmbp)(2)Br]OH.5(1)/(2)H(2)O and [Cu(dmbp)(2)Br](Br/OH).5(1)/(2)H(2)O (five coordinate monomers), and (dmbpH(2))CuBr(4).H(2)O (distorted tetrahedral monomers). The crystal structure determinations of these materials are reported. A common thread in their structural chemistry is the supramolecular architecture developed through interdigitation of the dmbp rings on neighboring molecular species. The interdigitation leads to layer structures in many of the materials. The distances between the interdigitated dmbp rings are in the range 3.4-3.7 A. The Cu(dmbp)(2)Br(+) species exhibits an exceptionally large distortion from tetrahedral geometry due to deviation of the dihedral angle between the mean planes of the Cu(dmbp) fragments from 90 degrees. The Cu(dmbp)(2)Br(+) cations have distorted trigonal bipyramidal geometry, the Br(-) ion occupying an equatorial position. The length of the Cu-Br bond in the Cu(dmbp)(2)Br(+) species is correlated with the change in dihedral angle between the planes of the two dmbp ligands. The mono-dmbp complexes show a greater variation in coordination geometry for the Cu(II) species, including distorted trigonal bipyramidal and augmented square planar 4 + 1 and 4 + 2 coordination.

Reaction of Cu(ClO4)2 with 2-methylpyrazine (mepz), 2,5-dimethylpyrazine (2,5-dmpz) or 2,6-dimethylpyrazine (2,6-dmpz) in aqueous solution yields the corresponding CuLn(ClO4)2(H2O)m (n = 2,4; m = 1,2,4). Single-crystal X-ray diffraction of Cu(mepz)2(ClO4)2(H2O)2 (1) reveals a roughly octahedral geometry with all ligands trans. Similarly, Cu(mepz)4(ClO4)2(H2O) (2) is pseudo-octahedral with one coordinated perchlorate and one H2O in the axial sites. The pyrazines are coordinated through the N(4) nitrogen atom in both 1 and 2. The magnetic susceptibilities of these compounds have been measured in the range 2–300 K. All the compounds behave as paramagnets. Conversely, reaction of Cu(ClO4)2 with 2,3-dimethylpyrazine in aqueous solution, or with mepz, 2,3-dmpz or 2,5-dmpz and NaBH4 or NaSCN in aqueous solution yields complexes of the type Cu2(L)3(ClO)4)2 or Cu2(L)(SCN)2, respectively. IR analysis suggests that the complexes are polymeric lattices of tri-coordinate copper(I) atoms bridged by the pyrazine ligands or the pyrazine and thiocyanate ligands, similar to the known structure of Cu2(2,3-dimethylpyrazine)3(ClO4)2.