Preface

Abstract

The FT-IR and Raman spectra of eight new complexes of formula ML₂Ni(CN)₄ (where M = Mn, Fe, Co, Ni, Cu or Cd and L = 2-chloropyridine; M = Ni or Cd and L = 2-bromopyridine) are reported. The spectroscopic results indicate that the complexes have structures consisting of corrugated polymeric layers of [M-Ni(CN)₄]∞ with 2-substituted pyridine molecules bound directly to the metal (M). For a given ligand (2-Clpy or 2-Brpy) the effects of metal-ligand bond formation on the ligand modes are examined. Metal-ligand bond strengths of the halo-derivatives of pyridine (L = 2-Clpy or 2-Brpy), inferred by the effects on frequency shifts of certain ligand modes, have also been compared.     

Vibrational spectroscopic studies of three dimensional host lattices formed by pyrazine bridges between tetracyanonickelate layers

Three dimensional host lattices have been developed by forming bridges with bidentate pyrazine molecules between adjacent tetracyanonickelate polymeric layers of Ni(II) or Cd(II). The Fourier-transform IR and Raman spectra (4000-200 cm^–1) of the compounds with the general formula M(pyz)Ni(CN)₄, (where M = Ni or Cd) are reported. These host lattices can include benzene molecules but it is found that aniline molecules cannot be included in these structures. They, however, form complexes with the formula M(an)₂Ni(CN)₄, by replacing pyrazine ligands. A monodentate pyrazine complex of Cd(II) with the formula Cd(pyz)₂Ni(CN)₄ has also been prepared.     

FT-IR Spectroscopic Investigation of Hofmann Td-Type Complexes of 2-, and 3-Chloropyridine

Hofmann-type modified clathrate hosts containing 2- or 3-chloropyridine molecules attached to metal (II) tetracyanocadmate frame, with a given formula: M(Clpy)₂Cd(CN)₄ where M = Mn, Ni or Cd; Clpy = 2- or 3-chloropyridine, have been synthesised for the first time. Their FT-IR spectra are reported in the 400–4000 cm^-1 region. All the vibrational modes of coordinated Clpy are characterised. The spectral features of the compounds studied are found to be similar to each other indicating that they have analogous structures. The coordination effect on the Clpy modes is analyzed.     

Synthesis,crystal structure and catalytic performance of bis (imino)pyridyl nickel complexes

Two new Ni(II) complexes of 2,6-bis[1-(2,6-diethylphenylimino)ethyl]pyridine (L¹), 2,6-bis[1-(4-methylphenylimino)ethyl]pyridine (L² ) have been synthesized and structurally characterized. Complex Ni(L¹)Cl₂?·?CH₃CN (1), exhibits a distorted trigonal bipyramidal geometry, whereas complex Ni(L¹)(CH₃CN)Cl₂ (2), is six-coordinate with a geometry that can best be described as distorted octahedral. The catalytic activities of complexes 1, 2, Ni{2,6-bis[1-(2,6-diisopropyl-phenylimino)ethyl]pyridine} Cl₂?·?CH₃CN (3), and Ni{2,6-bis[1-(2,6-dimethylphenylimino) ethyl]pyridine}Cl₂?·?CH₃CN (4), for ethylene polymerization were studied under activation with MAO.     

On the Search of Metallated Sulfonamides: Synthesis and X‐ray Characterization of the New Sulfathiazolato Nickel(II)‐Chelate Complex [Ni(STZ)2(Py)2]·2Py (STZ = Sulfathiazolato Anion; Sulfathiazole = N1‐2‐thiazolyl‐sulfanilamide; Py = Pyridine)

Sulfathiazole (HSTZ) reacts with triethylamine and Ni(CH₃COO)₂·4H₂O in methanol and further with pyridine to give the sulfathiazolato complex [Ni(STZ)₂(Py)₂]·2Py. In the new chelate complex the deprotonated sulfonamidic nitrogen atom does not take part in the coordination process, apparently retaining the negative charge. Two (STZ)^? moieties are symmetrically bonded to the Ni²⁺ ion through a thiazolyl nitrogen atom and an oxygen atom of the S(O)₂ group. Two pyridine molecules accomplish the fairly distorted octahedral coordination at the metal centre.     

Coordination behaviour of nicotinamide: an infrared spectroscopic study

A series of Hofmann-type complexes containing two nicotinamide(nia) molecules attached to transition metal (II) (M) tetracyanonickelate frame with the formula: M(nia)₂Ni(CN)₄ (where M=Mn, Co, Ni, Cu or Cd) have been synthesised for the first time. Metal (II) halide complexes of nicotinamide complexes of the type [M(nia)₂X₂ (M=Cd, Ni, Cu, Hg; X=Cl, Br) and Ni(nia)₄Br₂ nia=nicotinamide] have also synthesised. The FTIR spectra are reported in the 4000-400 cm⁻¹ region. Vibrational assignments are given for all the observed bands. The analysis of the vibrational spectra indicates that there are some structure-spectra correlations. A pronounced change was observed in the N-H stretching frequencies of the NH₂ group. It is proposed that the amide NH₂ group influence by the intramolecular hydrogen bond in the complexes. The coordination effect on the nicotinamide modes is analysed.     

57Fe Mössbauer spectroscopic and magnetic study of a spin-crossover polymer complex, Fe(3-chloropyridine)2Ni(CN)4

The coordination polymer Fe(3-chloropyridine)₂Ni(CN)₄ (2) has been prepared by a method similar to that for Fe(pyridine)₂Ni(CN)₄ (1). The complex (2) has been characterized by⁵⁷Fe Mössbauer spectroscopy and a SQUID technique.⁵⁷Fe Mössbauer and magnetic susceptibility data show that complex (2) exhibits spin-crossover behavior. The spin transition of (2) occurs between 120 and 80 K with very small hysteresis or without hysteresis. The temperature range of the spin transition in (2) is lower than that in (1). A residual high spin iron(II) fraction is observed at low temperatures in (2), being different from (1). SQUID data also show that samples treated differently yield different spin transition curves.     

Cu(bapen)M(CN)<Subscript>4</Subscript>·H<Subscript>2</Subscript>O complexes exhibiting chain-like structures (bapen = N,N′-bis(3-aminopropyl)-1,2-diaminoethane,M = Ni,Pd): preparations,crystal structures,spectroscopic and magnetic properties

Single crystals of Cu(bapen)Ni(CN)₄·H₂O and Cu(bapen)Pd(CN)₄·H₂O (bapen = N,N′-bis(3-aminopropyl)-1,2-diaminoethane) were isolated from the aqueous systems copper(II)—bapen—[M(CN)₄]^2? (M = Ni, Pd). Crystals of the two compounds are isostructural and are built up of two crystallographically independent quasi-linear chains [-Cu(bapen)-μ₂-NC-Ni(CN)₂-μ₂-CN-] _n and solvate water molecules. The copper(II) centers exhibit the usual distorted octahedral coordination with one tetradentate bapen ligand in the equatorial plane (mean Cu–N are 2.030 Å for Cu(bapen)Ni(CN)₄·H₂O and 2.018 Å for Cu(bapen)Pd(CN)₄·H₂O), while the axial positions are occupied by nitrogen atoms from μ₂-bridging cyanido ligands with longer Cu–N bonds (mean values are 2.544 Å for Cu(bapen)Ni(CN)₄·H₂O and 2.543 Å for Cu(bapen)Pd(CN)₄·H₂O). One of the two independent coordinated bapen ligands is disordered, as are the water molecules of crystallization. The Ni and Pd atoms in both studied compounds exhibit the usual square coordination with the bridging cyanido ligands trans to each other. Several OH···O, N–H···O and N–H···N hydrogen bonds enhance the stability of the structures. ESR spectra corroborated the presence of Jahn–Teller anisotropy at the copper(II) atoms. Magnetic studies in the temperature range 1.8–300 K reveal that both Cu(bapen)Ni(CN)₄·H₂O and Cu(bapen)Pd(CN)₄·H₂O follow Curie-Weiss laws with θ = ?0.51 K and θ = ?0.34 K, respectively, suggesting the presence of weak antiferromagnetic interactions.     

Synthesis and Crystal Structure of Cesium Nitratometalates(II), Cs2[M(NO3)4] (M = Mn,Co, Ni,Zn)

Crystalline cesium nitratometalates(II), Cs₂[M(NO₃)₄] (M = Mn ( I ), Co ( II ), Ni ( III ), and Zn ( IV )) were synthesized from M(NO₃)₂ · n H₂O and CsNO₃ by heating at 80–120 °C over 10–12 h. According to X-ray crystal structure analysis, the compounds are built from Cs⁺ cations and [M(NO₃)₄]^2– anions. The latter differ by the type of metal coordination: a dodecahedron for Mn in I (CN = 8, r_Mn–O 2.24–2.37 Å), a seven coordination for Co in II (CN = 4 + 3, r_Co–O 2.03–2.16 Å and 2.21–2.35 Å) and a tetrahedral distorted dodecahedron for Zn in IV (CN = 4 + 4, r_Zn–O 1.98–2.15 Å and 2.38–2.72 Å). Ni atom in III has a distorted octahedral NiO₆ environment provided by two unidentate and two bidentate NO₃ groups with Ni–O distances of 2.01–2.14 Å. The differences in metal coordination are discussed in terms of valence electron configurations, ionic radii, and the packing effects.     

An infrared and Raman spectroscopic study of some metal pyridine tetracyanonickelate complexes

The results of an infrared and Raman spectroscopic study are presented for seven new metal pyridine tetracyanonickelate complexes, M(py)₂Ni(CN)₄, M = Mn, Co, Fe, Ni, Cu, Zn and Cd. It is shown that the spectra are consistent with a proposed crystal structure for these complexes derived from X-ray diffraction measurements. The spectra can be clearly distinguished from those of analogous Hofmann-type clathrates with which the nickel complex had been previously confused. The copper complex has spectral features different from the other six compounds and an explanation is proposed in terms of a distortion of the general crystal structure due to the Jahn-Teller effect. Analysis of the single, sharp bands of coordinated pyridine offers a method of resolving some difficulties in earlier assignments of the normal modes of the free base. Several modes of coordinated pyridine have upward shifts in frequency compared to those in the free molecule and the shifts are metal dependent. An explanation, supported by a simple normal coordinate analysis on a model, is provided in terms of coupling with low frequency vibrations, particularly the M-N stretching frequency. Other vibrations of the Ni(CN)₄ group, which coordinates to the metals M to form a two-dimensional coordination polymer, are also metal dependent. It is similarly suggested that coupling with low frequency modes is the principal cause of the upward shifts in frequency.     

Guest-Dependent Pressure-Induced Spin Crossover in FeII4[MIV(CN)8]2 (M=Mo,W) Cluster-Based Material Showing Persistent Solvent-Driven Structural Transformations

Discrete molecular species that can perform certain functions in response to multiple external stimuli constitute a special class of multifunctional molecular materials called smart molecules. Herein, cyanido-bridged coordination clusters {[Fe^II(2-pyrpy)₂]₄[M^IV(CN)₈]₂} ⋅ 4 MeOH ⋅ 6 H₂O (M=Mo ( 1 solv ), M=W ( 2 solv ) and 2-pyrpy=2-(1-pyrazolyl)pyridine are presented, which show persistent solvent driven single-crystal-to-single-crystal transformations upon sorption/desorption of water and methanol molecules. Three full desolvation–resolvation cycles with the concomitant change of the host molecules do not damage the single crystals. More importantly, the Fe₄M₂ molecules constitute a unique example where the presence of the guests directly affects the pressure-induced thermal spin crossover (SCO) phenomenon occurring at the Fe^II centres. The hydrated phases show a partial SCO with approximately two out-of-four Fe^II centres undergoing a gradual thermal SCO at 1 GPa, while in the anhydrous form the pressure-induced SCO effect is almost quenched with only 15 % of the Fe^II centres undergoing high-spin to low-spin transition at 1 GPa.     

Low-dimensional Compounds Containing Cyano Groups. XIII. Structural–spectral Correlation of Copper Dicyanoargentates

The new mixed-valence mixed-metal complex Cu(py)₆Cu₂Ag₂(CN)₆ (py = pyridine) possesses a three dimensional polymeric crystal structure. The Cu(I) atom is tetrahedrally coordinated by two nitrogen atoms of pyridine molecules, by one nitrogen atom of the dicyanoargentate anion and by one carbon atom of the cyano group. Both the dicyanoargentate anion and the cyano group bridge the Cu(I) atom with neighboring Cu(II) atoms. These are hexacoordinated in the form of an elongated tetragonal bipyramid. The equatorial plane is formed by two nitrogen atoms from two pyridine molecules and two nitrogen atoms from bridging cyano groups. Axial positions are occupied by nitrogen atoms of the bridging [Ag(CN₂]⁻ anions. Correlation between structures of the title compound and seven other dicyanoargentates with their i.r. spectra has been studied. The coordination mode of [Ag(CN₂]⁻ anions in compounds Cu_8-xAg_x(tn)₃(CN)₁₀ x = 0.25, Cu(3-Mepy)₂Ag₂(CN)₄, Cu(py)₂Ag₂(CN)₄ and Cu(py)₄Ag₂(CN)₄ (tn is 1,3-diaminopropane, 3-Mepy is 3-methylpyridine) is predicted based on this correlation.     

[Ni(terpy)(H2O)]‐trans‐[Ni‐(μ‐CN)2‐(CN)2]n,a one‐dimensional linear tetra­cyano­nickelate chain

The one‐dimensional chain catena‐poly­[[aqua(2,2′:6′,2′′‐terpyridyl‐κ³N)­nickel(II)]‐μ‐cyano‐κ²N:C‐[bis­(cyano‐κC)nickelate(II)]‐μ‐cyano‐κ²C:N], [Ni(terpy)(H₂O)]‐trans‐[Ni‐μ‐(CN)₂‐(CN)₂]_n or [Ni₂­(CN)₄­(C₁₅H₁₁N₃)(H₂O)], consists of infinite linear chains along the crystallographic [10] direction. The chains are composed of two distinct types of nickel ions, paramagnetic octahedral [Ni(terpy)(H₂O)]²⁺ cations (with twofold crystallographic symmetry) and diamagnetic planar [Ni(CN)₄]^2? anions (with the Ni atom on an inversion center). The [Ni(CN)₄]^2? units act as bidentate ligands bridging through two trans cyano groups thus giving rise to a new example of a trans–trans chain among planar tetra­cyano­nickelate complexes. The coordination geometry of the planar nickel unit is typical of slightly distorted octahedral nickel(II) complexes, but for the [Ni(CN)₄]^2? units, the geometry deviates from a planar configuration due to steric interactions with the ter­pyridine ligands.     

Zur chemie des tris(cyclopentadienyl)uran(IV)-kations in wässriger lösung : II. Oligomere metallorganische tetracyanometallat-komplexe des uran(IV): Bis(tris(pentahapto-cyclopentadienyl)uran(IV))-tetracyanonickolat(II) bzw. -platinat(II)

Novel organometallic uranium(IV) complexes of the composition [(η⁵-Cp)₃U^IV]₂[Mn^II(CN)₄] Cp = C₅H₅, M = Ni or Pt) have been prepared from Cp₃UCl and K₂[M(CN)₄] in aqueous solution. On the basis of their properties they are characterized as layered oligomeric structures involving squared arrays of both the U and M atoms within the same plane, and a presumably trigonal bipyramidal coordination of the uranium(IV) ion.     

Bis -( bis -(1,3-diaminopropane)-copper(II) Tetracyanonickellate(II)) Tetrahydrate: Preparation, Characterization, and Crystal Structure of a Novel Molecular Tetracyanonickellate

 [Cu(tn)₂Ni(CN)₄]₂ċ4H₂O and Cu(tn)₂Ni(CN)₄ (tn = 1,3-diaminopropane) were prepared and characterized. The hydrate is unstable on air and readily dehydrates to Cu(tn)₂Ni(CN)₄. Crystal structure analysis of the hydrate at 150 K revealed a novel tetranuclear molecular structure of the tetracyanonickellate. The building elements are two [Cu(tn)₂]²⁺ cations (coordination numbers of Cu: 5 and 6, respectively), two [Ni(CN)₄)²⁻ anions, and crystal water. The two cations are linked by one tetracyanonickellate anion via bridging cyano groups placed in cis positions. The second anion is bound weakly (Cu-N = 2.82 ?) via one μ₂-bridging cyano ligand. The tetranuclear molecules and pairs of solvate water molecules are linked by strong hydrogen bonds, thus forming infinite planes which are linked in the third dimension by considerably weaker hydrogen bonds.     

Bis-(bis-(1,3-diaminopropane)-copper(II) Tetracyanonickellate(II)) Tetrahydrate: Preparation, Characterization, and Crystal Structure of a Novel Molecular Tetracyanonickellate

Summary.  [Cu(tn)₂Ni(CN)₄]₂ċ4H₂O and Cu(tn)₂Ni(CN)₄ (tn = 1,3-diaminopropane) were prepared and characterized. The hydrate is unstable on air and readily dehydrates to Cu(tn)₂Ni(CN)₄. Crystal structure analysis of the hydrate at 150 K revealed a novel tetranuclear molecular structure of the tetracyanonickellate. The building elements are two [Cu(tn)₂]²⁺ cations (coordination numbers of Cu: 5 and 6, respectively), two [Ni(CN)₄)²⁻ anions, and crystal water. The two cations are linked by one tetracyanonickellate anion via bridging cyano groups placed in cis positions. The second anion is bound weakly (Cu-N = 2.82 ?) via one μ₂-bridging cyano ligand. The tetranuclear molecules and pairs of solvate water molecules are linked by strong hydrogen bonds, thus forming infinite planes which are linked in the third dimension by considerably weaker hydrogen bonds. Received May 9, 2000. Accepted (revised) August 21, 2000     

Vibrational Spectroscopic Investigation of the Hofmann-type Clathrates: M(piperidine)2Ni(CN4. G (M=Co, Ni or Cu; G = benzene derivatives)

Infrared spectra of M(piperidine)₂Ni(CN)₄.0.5G (M=Co, Ni or Cu;G= chlorobenzene, 1,2-dichlorobenzene or 1,3-dichlorobenzene; M=Co or Ni;G=1,4-dichlorobenzene) compounds are reported. The piperidine molecules inthe host permit the inclusion of bulky guest molecules. The spectral featuressuggest that the compounds are similar in structure to the Hofmann-type clathrates.     

Vibrational Spectroscopic Studies on the Hofmann Type Clathrates: M(1,6-diaminohexane)Ni(CN) 4 .G (M = Co, Ni or Cd; G = chlorobenzene, 1,2-, 1,3- or 1,4-dichlorobenzene)

New Hofmann-diaminohexane(dahxn)-type clathrates of the form M(1,6-dahxn)Ni(CN)₄.G (M = Co, Ni or Cd; G = chlorobenzene, 1,2-, 1,3 or 1,4-dichlorobenzene) were prepared inpowder form and their infrared spectra are reported. The spectral data suggest that these compounds are similar in structure to those of the Hofmann-diam-type clathrates. Their structure consists of planar polymeric layers, {M–Ni(CN)₄}, formedfrom Ni(CN)₄ anions coordinated to the bridging 1,6-diaminohexane molecules bound directly to the metal (M). The M atoms are bound to four N atoms of the CN ions and, the Ni atoms are surrounded by four C atoms of the CN groups in a square-planar layer.     

An infrared spectroscopic study of dianiline-metal(ii) tetracyanometalate complexes

The results of an IR spectroscopie study are presented for six new dianiline metal tetracyanometalate complexes, M(an)₂M'(CN)₄ (M = Mn, Fe, Co or Cu and M'= Ni; M = Ni or Cd and M' = Pt; an = aniline). Their structure consists of polymeric layers of (M-M'(CN)₄)∞ with the aniline molecules bound directly to metal (M). For these series of isomorphous complexes there is a correlation between the shifts of some aniline bands on coordination and the strength of metal-nitrogen bonding measured by the v(M-N) value. Low temperature (83 K) data are also reported and it is noted that whilst the aniline ring and CH mode frequencies are virtually insensitive to temperature, the NH₂ wagging, NH₂ rocking and the metal-ligand stretching v(M-N) frequencies increase with decreasing temperature, whilst the v(NH₂) modes decrease with decreasing temperature. The vibrational frequencies of the M'(CN)₄ group are also temperature dependent and increase in value upon cooling the sample to 83 K. The changes are thought to be due to a slight contraction in the cavity size with decreasing temperature. The relationship between these complexes and Hofmann-type aniline clathrates, M(NH₃)₂M'(CN)₄ · 2 an, is indicated.     

Interlayer inclusion of tetracyanonickelate anion and water molecules: The crystal and molecular structure of [-ZN(en)2-μ-(NC)2-NI-μ -(CN)2-ZN(en) -] n 2n+ ·n[NI(CN)4]2− · 3n H2O

The crystal structure of [Zn(en)₂- (NC)₂Ni(CN)₂ Zn(en)][Ni(CN)₄]· 3 H₂O consists of infinite positively charged wave-shaped layers of composition [Zn(en)₂-(NC)₂Ni(CN)₂- Zn(en)] _n ²ⁿ⁺ with the [Ni(CN)₄]^2– anions and water molecules included between them. Both Ni atoms exhibit square-planar coordination. The chelate bonded en (=ethylenediamine) and N-bonded cyano ligands around two independent zinc atoms form a deformed tetrahedron and a deformed octahedron, respectively. Yellow needles of the complex belong to the orthorhombic space groupPbcm witha = 6.977(1),b = 25.407(4),c = 14.876(2)Å,Z = 4,D _m = 1.74(1) g cm^–3 andD _c = 1.739 g cm^–3. The structure was refined toR = 6.31 %.