Reactions of Cu(hfacac)(2)center dot H2O (hfacac = hexafluoroacetylacetonate) with bidentate ligands. Preparation, characterization, and X-ray structures of the molecular complexes Cu(hfacac)(2)(pyrazine)(2) and Cu(hfacac)(2)(3-cyanopyridine)(2) and the one-dimensional coordination polymers Cu(hfacac)(2)(1,2-bis(4-pyridyl)ethane) and Cu(hfacac)(2)(4,4 '-trimethylenebipyridine)

Reactions of Cu(hfacac)(2). H2O (hfacac = hexafluoroacetylacetonate) with p yrazine, 3-cyanopyridine, 1,2-bis(4-pyridyl)ethane, and 4,4'-trimethylenebi pyridine in methylene chloride have been studied. Two types of products wer e obtained and crystallographically characterized: compounds 1 (Cu(hfacac)( 2)(pyrazine)(2), orthorhombic, Pbca; a = 9.839(2) Angstrom, b = 17.984(2) A ngstrom, c = 13.572(2) Angstrom, Z = 4) and 2 (Cu(hfacac)(2)(3-cyanopyridin e)(2), triclinic, P (1) over bar, a = 13.175(2) Angstrom, b = 13.955(2) Ang strom, c = 7.936(2) Angstrom, alpha = 104.29(2)degrees, beta = 105.90 degre es, gamma = 81.47(1)degrees, Z = 2) were isolated as molecular complexes, w hile compounds 3 (Cu(hfacac)(2)(1,2-bis(4-pyridyl)ethane, monoclinic, P2(1) /c, a = 7.922(1) Angstrom, b = 16.266(4) Angstrom, c = 10.163(2) Angstrom, beta = 93.83(1)degrees Z = 2) and 4 (Cu(hfacac)(2)(4,4'-trimethylenebipyrid ine), monoclinic, Pc, a = 7.940(1) Angstrom, b = 9.691(2) Angstrom, c = 18. 539(3) Angstrom, beta = 95.83(2)degrees, Z = 2) were isolated as one-dimens ional infinite polymeric chains. The structures were further characterized by infrared spectroscopy, thermogravimetry, and elemental analysis; additio nally, the magnetic behavior of all compounds was investigated and found to follow the Curie law. All four compounds feature similar 4 + 2 pseudooctah edral coordination environments around the Cu(II) centers composed of squar e-planar Cu(hfacac)(2) units with the N-donor ligands occupying the trans p ositions. The length of the N-donor ligands determines the formation of eit her molecular complexes (1 and 2, short ligands) or infinite polymeric stru ctures (3 and 4, longer ligands). Important C-F ... H-C hydrogen-bonding in teractions in compounds 1 and 3 play a significant role in aligning the mol ecules and the polymer strands in the crystalline solids.