Mária Hvastijová

Tricyanomethanide and Dicyanamide Complexes of Cu(II), Ni(II), Co(II), Their Structures and Properties

Abstract This review summarizes data for all known tricyanomethanide and dicyanamide compounds of copper(II), nickel(II) and cobalt(II). The possible bonding modes of [C(CN)3]− and [N(CN)2]− ions and their influence on infrared spectra are demonstrated. Preparative methods are briefly described and structural data for crystallographically characterized compounds are given. Data for electronic and ESR spectra, magnetic susceptibilities, vibrational and ESCA spectra are reviewed and consequences following from these techniques for structural characteristics are discussed. The most striking features of the behaviour of both pseudohalide ligands are their polydentate character and ability for bridging. This ability is revealed by many physical properties, especially by the temperature dependence of magnetic susceptibilities, in which exchange interaction through pseudohalide bridges is manifested. Reactivity of C(CN)3 and N(CN)2 groups in the coordination sphere of Cu(II) and Ni(II) is mentioned.

A linkage isomeric pair of bis(dicyanamido)-bis(imidazole)copper(II) complexes with considerably different magnetic properties

Abstract Two isomeric compounds (α and β) of the composition Cu{N(CN)2}2(imidazole)2 were prepared and studied by IR, far-IR, electronic and ESR spectra, as well as by temperature-dependent (down to 4.2 K) magnetic susceptibility measurements. A sixcoordinate polymeric chain structure is assumed with different bridging functions of the N(CN)2group, viz. through both cyanide nitrogens and through amide and cyanide nitrogens in the α- and β-isomers, respectively. The temperat

Cyanamidonitrate–copper(II) complexes of imidazole ligands: X-ray crystallography and physical investigation

Abstract New cyanamidonitrate–copper(II) complexes [Cu(NO2NCN)2Ln] (L=imidazole (iz), n=2; L=iz, 1-, 2- or 4-methylimidazole (meiz), n=4) have been isolated and characterised by IR, electronic and ESR spectroscopy. The crystal structures of 1- and 4-meiz complexes have been determined by X-ray crystallography; the structure of [Cu(NO2NCN)2(iz)2] is known (J. Kožisek, J.G. Diaz, M. Hvastijova, L. Jager, Acta Crystallogr., Sect. C 53 (1997) 703). The crystal structure of the first two compounds consists of [Cu(NO2NCN)2L4] units, in which the central CuII atoms are pseudo-octahedrally coordinated by six nitrogen atoms. Four of them, in equatorial planes, originate from meiz molecules and two, in axial positions, are nitrile nitrogens from the NO2NCN− anions. Influence of hydrogen bonds on equatorial–axial bond length correlation was ascertained. In the ESR spectra of the [Cu(NO2NCN)2L4] compounds copper hyperfine splitting is resolved. For all complexes, weak lines corresponding to the ΔMs=2 transitions appear. The spectrum of [Cu(NO2NCN)2(iz)4] in frozen methanolic solution shows 16-fold nitrogen splitting of the perpendicular band.

Addition of methanol to dicyanamide in the Cu(II) coordination sphere: structure of bis{bis(methoxycarbimido)aminato }copper(II)

During investigation of the system Cu(II)―N-(CN) 2 − ―py―CH 3 OH―H 2 O (py=pyridine), violet red crystals of a copper(II) complex were separated. An X-ray diffraction study was undertaken in order to elucidate the structure of the compound obtained and the chemical reaction of its synthesis

Magnetic and spectral properties of the coligand isomer pair: Cu{N(CN)2}2(pyrazole)2 and Cu{pyrazole · N(CN)2}2

SummaryNew coligand isomers of composition Cu{N(CN)2}2(pz)2 and Cu{pz · N(CN)2}2 (pz = pyrazole) were prepared and studied by measuring their magnetic susceptibilities up to 4.2K and by aid of their e.s.r., ligand field and i.r. spectra. The susceptibility data have been analysed with various models for the exchange-coupled copper(II) polymers. It is shown that the resultant exchange coupling is ferromagnetic for Cu{N(CN)2}2(pz)2 (J ∼ 1.1 - 1.4 cm−1) but antiferromagnetic for Cu{pz · N(CN)2}2 (J ≈ −0.4 cm−1). A polymeric chain structure is proposed for Cu{N(CN)2}2(pz)2 havingpseudo-octahedrally coordinated copper(II) and CN-bridging dicyanamide ligands. Its coligand isomer contains anionic chelate ligands, formed by nucleophilic addition between N(CN)2 and pz in the copper(II) coordination sphere, and giving with this central atom a square-planar system. Definite, but slight axial interaction takes place between these structure units.

Structural characterization of nitrosodicyanomethanide and dicyanamide complexes of copper(II), nickel(II) and cobalt(II) with imidazole and 1-methylimidazole. X-ray crystallographic evidence of unusual nitrosodicyanomethanide O-bonding in Cu{ONC(CN)2}2 (1-methylimidazole)4

Abstract Pseudohalide complexes of the type M{ONC(CN)2}2L2, with M = Cu, L = imidazole (iz), 1-methylimidazole (meiz); M = Ni, Co, L = meiz, Cu{ONC(CN)2}2(meiz)4 M{ONC(CN)2}2(iz)4, with M = Ni, Co, and M{N(CN)2}2L2, with M = Cu, Co, L = meiz; M = Ni, L = iz, meiz have been prepared and characterized by spectroscopic and magnetic techniques. The crystal structure of Cu{ONC(CN)2}2(meiz)4 has been determined by the X-ray diffraction method. The CuII environment is elongated pseudooctahedral, composed of four tertiary meiz nitrogens and two nitrosodicyanomethanide oxygens in longer axial distances. According to spectroscopic results, the remaining compounds show octahedral (Ni, Co) or pseudooctahedral (Cu) structures, realized in the M : L = 1:2 and probably also in the 1:4 compounds by bridging pseudohalide function. Such bridging is evidenced by magnetic properties of Cu{ONC(CN)2}2(meiz)2, being affected by exchange coupling between the paramagnetic metal ions.

Structural, spectral and magnetic investigations of various types of compounds and their isomers isolated from the system copper(II)–C(CN)3––pyrazole

From the system CuII–C(CN)3––Hpz (Hpz = pyrazole) the following compounds were isolated: [Cu{C(CN)3}(Hpz)4][C(CN)3]1, [Cu{C(CN)3}2(Hpz)3]2, α-[Cu{C(CN)3}2(Hpz)2]3, β-[Cu{C(CN)3}2(Hpz)2]4 and [Cu{Hpz·C(CN)3}2]5. They were studied by the use of spectroscopic and cryomagnetic methods. The structures of 1 and 2 were refined to R values of 0.0369 and 0.0374 for 1346 and 2066 independent reflections respectively. Compound 1 crystallises in space group P21/c, with a= 9.568(4), b= 16.692(7), c= 14.957(9)A, β= 94.05(4)° and Z= 4; 2 crystallises in space group P, with a= 7.607(4), b= 8.942(6), c= 16.027(10)A, α= 95.95(6), β= 90.83(5), γ= 106.88(5)° and Z= 2. Both compounds show elongated pseudo-octahedral copper environments, with the Hpz molecules in the equatorial plane. In 1 one C(CN)3 group bridges the CuII atoms in axial positions while the second group is anionic. Compound 2 contains mono- as well as bi-dentate bridging C(CN)3 groups; the latter join the basic structure units into binuclear species. Weak ferromagnetic coupling operates between the copper(II) centres inside the dimers. Physical measurements show that compounds 3 and 4 display rhombic octahedral arrangements around CuII in which all C(CN)3 groups are bridging. The α and β compounds are distortion isomers. Compound 5, a coligand isomer with respect to 3 and 4, contains new anionic chelate ligands, HNC(pz)CH(CN)2–, formed by nucleophilic addition. In all these three compounds polymeric chains are present in which and between which there is magnetic interaction.

Magnetism and spectroscopy of compounds Cu{C(CN)3}2(tmpz)2 and Cu{N(CN)2}2(tmpz)2 where tmpz = 3,4,5-trimethylpyrazole

Abstract The title compounds were studied by measuring their magnetic susceptibilities up to 4.2 K and by use of their IR, ligand field and ESR spectra. Distorted octahedral structures are ascertained for both compounds, the C(CN)3 or N(CN)2 groups having a bidentate bridging function. Spin exchange coupling takes place in both compounds, being both antiferromagnetic and ferromagnetic in nature, the latter appears to prevail at low temperatures.

Ligand and distortion isomers isolated from the Cu(II)NCO−-pyrazole system

Abstract From the Cu(II)NCO−-pyrazole (pz) system two pairs of isomeric compounds were isolated. The IR spectra show that the first pair represents the cyanato complexes Cu(NCO)2(pz)2, while the second includes the compounds Cu(pz.NCO)2, containing 1-carbamoylpyrazolate anions as chelating ligands. According to the ligand field spectra the compounds of each pair differ in the distortion of the pseudooctahedral Cu(II) atom environment. The ESR spectra and the temperature dependent magnetic data reveal a considerable exchange interaction.

X-ray crystallographic and physical investigation of tricyanomethanide and dicyanamide complexes of cobalt(II) with imidazole and its methyl derivatives

SummaryReaction of CoII with N(CN)inf2sup− or C(CN)inf3sup− in the presence of imidazole (iz) or its methyl derivatives (2-meiz and 4-meiz) gave eight compounds of CoII: ligand stoichiometry 1∶2, including two isomeric pairs (α and β) for the complexes [Co{C(CN)3}2(2-meiz)2] and [Co{C(CN)3}2-(4-meiz)2]. The complexes were studied by electronic and i.r. spectroscopies. For α-[Co{C(CN)3}2(2-meiz)2] singlecrystal X-ray analysis was performed; its crystal structure consists of one-dimensional chains, formed by C(CN)inf3sup− anions bridging between the CoII atoms. The CoII atom is nearly octahedrally coordinated by two tertiary nitrogens of 2-meiz and four nitrogens of C(CN)inf3sup−. The spectra of these compounds and of the complexes with iz, as well as that of α-[Co{C(CN)3}2(4-meiz)2], indicate all these compounds to have basically the same bridging polymeric octahedral structure. However, the spectra indicate distorted tetrahedral structures for the remaining compounds.