Synthesis, crystal structure and properties of chlorido-tetra-kis-(pyridine-3-carbo-nitrile)-thio-cyanato-iron(II)

Reaction of FeCl2·4H2O with KSCN and 3-cyano-pyridine (pyridine-3-carbo-nitrile) in ethanol accidentally leads to the formation of single crystals of Fe(NCS)(Cl)(3-cyano-pyridine)4 or [FeCl(NCS)(C6H4N2)4]. The asymmetric unit of this compound consists of one FeII cation, one chloride and one thio-cyanate anion that are located on a fourfold rotation axis as well as of one 3-cyano-pyridine coligand in a general position. The FeII cations are sixfold coordinated by one chloride anion and one terminally N-bonding thio-cyanate anion in trans-positions and four 3-cyano-pyridine coligands that coordinate via the pyridine N atom to the FeII cations. The complexes are arranged in columns with the chloride anions, with the thio-cyanate anions always oriented in the same direction, which shows the non-centrosymmetry of this structure. No pronounced inter-molecular inter-actions are observed between the complexes. Initially, FeCl2 and KSCN were reacted in a 1:2 ratio, which lead to a sample that contains the title compound as the major phase together with a small amount of an unknown crystalline phase, as proven by powder X-ray diffraction (PXRD). If FeCl2 and KSCN is reacted in a 1:1 ratio, the title compound is obtained as a nearly pure phase. IR investigations reveal that the CN stretching vibration for the thio-cyanate anion is observed at 2074 cm-1, and that of the cyano group at 2238 cm-1, which also proves that the anionic ligands are only terminally bonded and that the cyano group is not involved in the metal coordination. Measurements with thermogravimetry and differential thermoanalysis reveal that the title compound decomposes at 169°C when heated at a rate of 4°C min-1 and that the 3-cyano-pyridine ligands are emitted in two separate poorly resolved steps. After the first step, an inter-mediate compound with the composition Fe(NCS)(Cl)(3-cyano-pyridine)2 of unknown structure is formed, for which the CN stretching vibration of the thio-cyanate anion is observed at 2025 cm-1, whereas the CN stretching vibration of the cyano group remain constant. This strongly indicates that the FeII cations are linked by μ-1,3-bridg-ing thio-cyanate anions into chains or layers.

Synthesis, crystal structure and thermal properties of tetra-kis-(3-methyl-pyridine-κN)bis-(thio-cyanato-κN)nickel(II)

Reaction of Ni(NCS)2 with 3-methyl-pyridine in water leads to the formation of crystals of the title compound, [Ni(NCS)2(C6H7N)4]. All of them are of poor quality and non-merohedrally twinned but a refinement using data in HKLF-5 format leads to a reasonable structure model and reliability factors. The crystal structure of the title compound consists of discrete complexes, in which the nickel cations are sixfold coordinated by two terminal N-bonded thio-cyanate anions and four 3-methyl-pyridine ligands within slightly distorted octa-hedra. One of the 3-methyl-pyridine ligands is disordered and was refined using a split model. The discrete complexes are arranged into layers. X-ray powder diffraction proves that pure samples have been obtained, and in the IR spectrum, the CN stretching vibration is observed at 2072 cm-1, in agreement with the presence of only terminally coordinated thio-cyanate anions. Comparing the calculated powder pattern with those of the residues obtained by solvent removal from several solvates already reported in the literature proves that, in each case, this crystalline phase is formed. Assessing the crystal structures of the solvates in comparison with that of the ansolvate reveals some similarities.

Synthesis, crystal structure and thermal properties of bis-(aceto-nitrile-κN)bis-(3-bromo-pyridine-κN)bis-(thio-cyanato-κN)cobalt(II)

Single crystals of the title compound, [Co(NCS)2(C5H4BrN)2(C2H3N)2], were obtained by the reaction of Co(NCS)2 with 3-bromo-pyridine in aceto-nitrile. The CoII cations lie on crystallographic inversion centers and are coordinated by two N-bonded thio-cyanate anions, two 3-bromo-pyridine and two aceto-nitrile ligands thereby forming slightly distorted CoN6 octa-hedra. In the crystal, these complexes are linked by C-H⋯S and C-H⋯N hydrogen bonds into a three-dimensional network. In the direction of the crystallographic b-axis, the complexes are arranged into columns with neighboring 3-bromo-pyridine ligands stacked onto each other, indicating π-π inter-actions. The CN stretching vibration of the thio-cyanate anions is observed at 2066 cm-1, in agreement with the presence of only N-bonded anionic ligands. TG-DTA measurements reveal that in the first mass loss the aceto-nitrile ligands are removed and that in the second step, half of a 3-bromo-pyridine ligand is lost, leading to the formation of a polymeric compound with the composition [(Co(NCS)2)2(C5H4BrN)3] n already reported in the literature.

Co(NCS)2 Chain Compound with Alternating 5- and 6-Fold Coordination: Influence of Metal Coordination on the Magnetic Properties

The reaction of Co(NCS)₂ with 3-bromopyridine leads to the formation of discrete complexes [Co(NCS)₂(3-bromopyridine)₄] (1), [Co(NCS)₂(3-bromopyridine)₂(H₂O)₂] (2), and [Co(NCS)₂(3-bromopyridine)₂(MeOH)₂] (3) depending on the solvent. Thermogravimetric measurements on 2 and 3 show a transformation into [Co(NCS)₂(3-bromopyridine)₂]_n (4), which upon further heating is converted to [{Co(NCS)₂}₂(3-bromopyridine)₃]_n (5), whereas 1 transforms directly into 5 upon heating. Compound 5 can also be obtained from solution, which is not possible for 4. In 4 and 5, the cobalt(II) cations are linked by pairs of μ-1,3-bridging thiocyanate anions into chains. In compound 4, all cobalt(II) cations are octahedrally coordinated (OC-6), as is usually observed in such compounds, whereas in 5, a previously unkown alternating 5- and 6-fold coordination is observed, leading to vacant octahedral (vOC-5) and octahedral (OC-6) environments, respectively. In contrast to 4, the chains in 5 are very efficiently packed and linked by π···π stacking of the pyridine rings and interchain Co···Br interactions, which is the basis for the formation of this unusual chain. The spin chains in 4 demonstrate ferromagnetic intrachain exchange and much weaker interchain interactions, as is usually observed for such linear chain compounds. In contrast, compound 5 shows almost single-ion-like magnetic susceptibility, but the magnetic ordering temperature deduced from specific heat measurements is twice as high as that in 4, which might originate from π···π stacking and Co···Br interactions between neighboring chains. More importantly, unlike all linear Co(NCS)₂ chain compounds, a dominant antiferromagnetic exchange is observed for 5, which is explained by density functional theory calculations predicting an alternating ferro- and aniferromagnetic exchange within the chains. Theoretical calculations on the two different cobalt(II) ions present in 5 predict an easy-axis anisotropy that is much stronger for the octahedral cobalt(II) ion than for the one with the vacant octahedral coordination, with the magnetic axes of the two ions being canted by an angle of 84°. This almost orthogonal orientation of the easy axis of magnetization for the two cobalt(II) ions is the rationale for the observed non-Ising behavior of 5.

Syntheses and crystal structures of the ethanol, acetonitrile and diethyl ether Werner clathrates bis-(iso-thio-cyanato-κN)tetra-kis-(3-methyl-pyridine-κN)nickel(II)

The reaction of nickel(II)thio-cyanate with 3-methyl-pyridine (3-picoline; C6H7N) in different solvents leads to the formation of crystals of bis-(iso-thio-cyanato-κN)tetra-kis-(3-methyl-pyridine-κN)nickel(II) as the ethanol disolvate, [Ni(NCS)2(C6H7N)4]·2C2H5OH (1), the acetonitrile disolvate, [Ni(NCS)2(C6H7N)4]·2CH3CN (2), and the diethyl ether monosolvate, [Ni(NCS)2(C6H7N)4]·C4H10O (3). The crystal structures of these compounds consist of NiII cations coordinated by two N-bonded thio-cyanate anions and four 3-methyl-pyridine ligands to generate NiN6 octa-hedra with the thio-cyanate groups in a trans orientation. In compounds 1 and 2 these complexes are located on centers of inversion, whereas in compound 3, they occupy general positions. In the crystal structures, the complexes are packed in such a way that cavities are formed in which the solvent mol-ecules are located. Compounds 1 and 2 are isotypic, which is not the case for compound 3. In compounds 1 and 2 the solvate mol-ecules are disordered, whereas they are fully ordered in compound 3. Disorder is also observed for one of the 3-methyl-pyridine ligands in compound 2. Powder X-ray diffraction and IR measurements show that at room temperature all compounds decompose almost immediately into the same phase, as a result of the loss of the solvent mol-ecules.

Syntheses, crystal structures and properties of tetra-kis-(3-methyl-pyridine-κN)bis-(iso-thio-cyanato-κN)manganese(II) and tetra-kis-(3-methyl-pyridine-κN)bis-(iso-thio-cyanato-κN)iron(II)

The reaction of Mn(NCS)2 or Fe(NCS)2 with 3-methyl-pyridine (C6H7N) leads to the formation of two isostructural compounds with compositions [Mn(NCS)2(C6H7N)4] (1) and [Fe(NCS)2(C6H7N)4] (2). IR spectroscopic investigations indicate that only terminally coordinated thio-cyanate anions are present. This is confirmed by single-crystal structure analysis, which shows that their crystal structures consist of discrete centrosymmetric complexes, in which the metal cations are octa-hedrally coordinated by two N-bonded thio-cyanate anions and four 3-methyl-pyridine ligands. X-ray powder diffraction (XRPD) proves that pure samples have been obtained. Thermogravimetric measurements show that decomposition starts at about 90°C and that the two coligands are removed in one step for 1 whereas for 2 no clearly resolved steps are visible. XRPD measurements of the residue obtained after the first mass loss of 1 show that a new and unknown crystalline compound has been formed.

Synthesis, crystal structure and magnetic properties of coordination compounds of Mn(NCS)2 with the 3-bromopyridine ligand

Reactions of Mn(NCS)2 with 3-bromopyridine in acetonitrile lead to the formation of Mn(NCS)2(3-bromopyridine)4 (1) and Mn(NCS)2(3-bromopyridine)2(MeCN)2 (2) that were characterized by single crystal X-ray diffraction. Compounds 1 and 2 consist of discrete complexes, in which the Mn(II) cations are octahedrally coordinated by two trans-N-bonding thiocyanate anions and four pyridine (1) or two pyridine and two acetonitrile ligands (2). Thermoanalytical measurements on 1 and 2 have shown that upon heating half of the 3-bromopyridine co-ligands from 1 or both acetonitrile ligands from 2 are removed leading to a crystalline phase with the composition [Mn(NCS)2(3-bromopyridine)2] n (3-II). From dry n-butanol a phase with the same composition was obtained (3-I) that corresponds to a polymorphic or isomeric form of 3-II. Crystal structure analysis of 3-I shows that in this form the Mn cations are linked by pairs of anionic ligands into linear chains. The results of magnetic measurements on 3-I show antiferromagnetic interactions along the chains and the analysis of the magnetic susceptibility using the Fisher model for chains gave a J value of −5.76(5) K.

Crystal structures of two Co(NCS)2 urotropine coordination compounds with different Co coordinations

The reaction of Co(NCS)2 with urotropine in ethanol leads to the formation of two different compounds, namely, bis-(ethanol-κO)bis-(hexa-methyl-ene-tetra-mine-κN)bis-(thio-cyanato-κN)cobalt(II)-di-aqua-κ 2O-bis-(hexa-methyl-ene-tetra-mine-κN)bis-(thio-cyanato-κN)cobalt(II)-ethanol-hexa-methyl-ene-tetra-mine (1.2/0.8/1.6/4), [Co(NCS)2(C6H12N4)2(C2H6O)2]1.2·[Co(NCS)2(C6H12N4)2(H2O)2]0.8·1.6C2H6O·4C6H12N4, 1, and tris-(ethanol-κO)(hexa-methyl-ene-tetra-mine-κN)bis(thio-cyanato-κN)cobalt(II), [Co(NCS)2(C6H12N4)(C2H6O)3], 2. In the crystal structure of compound 1, two crystallographically independent discrete complexes are observed that are located on centres of inversion. In one of them, the Co cation is octa-hedrally coordinated to two terminal N-bonded thio-cyanate anions, two urotropine ligands and two ethanol mol-ecules, whereas in the second complex 80% of the coordinating ethanol is exchanged by water. Formally, compound 1 is a mixture of two different complexes, i.e. di-aqua-dithio-cyanato-bis-(urotropine)cobalt(II) and di-ethano-ldi-thio-cyanato-bis-(uro-trop-ine)cobalt(II), that contain additional ethanol and urotropine solvate mol-ecules leading to an overall composition of [Co(NCS)2(urotropine)2(ethanol)1.2(H2O)0.8·0.8ethanol·4urotropine. Both discrete complexes are linked by inter-molecular O-H⋯O and O-H⋯N hydrogen bonding and additional urotropine solvate mol-ecules into chains, which are further connected into layers. These layers combine into a three-dimensional network by pairs of centrosymmetric inter-molecular C-H⋯S hydrogen bonds. In the crystal structure of compound 2, di-thio-cyanato-(urotropine)tri-ethano-lcobalt(II), the cobalt cation is octa-hedrally coordinated to two terminal N-bonded thio-cyanate anions, one urotropine ligand and three ethanol mol-ecules into discrete complexes, which are located in general positions. These complexes are linked by inter-molecular O-H⋯N hydrogen bonding into layers, which are further connected into a three-dimensional network by inter-molecular C-H⋯S hydrogen bonding.

Crystal structure of di-ethano-lbis(thio-cyanato)-bis(urotropine)cobalt(II) and tetra-ethano-lbis(thio-cyanato)-cobalt(II)-urotropine (1/2)

The reaction of one equivalent Co(NCS)2 with four equivalents of urotropine (hexa-methyl-ene-tetra-mine) in ethanol leads to the formation of two compounds, namely, bis-(ethanol-κO)bis-(thio-cyanato-κN)bis-(urotropine-κN)cobalt(II), [Co(NCS)2(C6H12N4)2(C2H6O)2] (1), and tetra-kis-(ethanol-κO)bis-(thio-cyanato-κN)cobalt(II)-urotropine (1/2), [Co(NCS)2(C2H6O)4]·2C6H12N4 (2). In 1, the Co cations are located on centers of inversion and are sixfold coordinated by two terminal N-bonded thio-cyanate anions, two ethanol and two urotropine ligands whereas in 2 the cobalt cations occupy position Wyckoff position c and are sixfold coordinated by two anionic ligands and four ethanol ligands. Compound 2 contains two additional urotropine solvate mol-ecules per formula unit, which are hydrogen bonded to the complexes. In both compounds, the building blocks are connected via inter-molecular O-H⋯N (1 and 2) and C-H⋯S (1) hydrogen bonding to form three-dimensional networks.

Synthesis, crystal structure and thermal properties of bis-(1,3-di-cyclo-hexyl-thio-urea-κS)bis(iso-thiocyanato-κN)cobalt(II)

Crystals of the title compound, [Co(NCS)2(C13H24N2S)2], were obtained by the reaction of Co(NCS)2 with 1,3-di-cyclo-hexyl-thio-urea in ethanol. Its crystal structure consists of discrete complexes that are located on twofold rotation axes, in which the CoII cations are tetra-hedrally coordinated by two terminal N-bonded thio-cyanate anions and two 1,3-di-cyclo-hexyl-thio-urea ligands. These complexes are linked via inter-molecular N-H⋯S and C-H⋯S hydrogen bonding into chains, which elongate in the b-axis direction. These chains are closely packed in a pseudo-hexa-gonal manner. The CN stretching vibration of the thio-cyanate anions located at 2038 cm-1 is in agreement with only terminal bonded anionic ligands linked to metal cations in a tetra-hedral coordination. TG-DTA measurements prove the decomposition of the compound at about 227°C. DSC measurements reveal a small endothermic signal before decomposition at about 174°C, which might correspond to melting.

Synthesis and crystal structure of di-aqua-bis-(hexa-methyl-enetramine-κN)bis-(thio-cyanato-κN)cobalt(II)-hexa-methyl-ene-tetra-mine-aceto-nitrile (1/2/2)

The crystal structure of the title solvated coordination compound, [Co(NCS)2(C6H12N4)2(H2O)2]·2C6H12N4·2C2H3N, consists of discrete complexes in which the Co2+ cations (site symmetry ) are sixfold coordinated by two N-bonded thio-cyanate anions, two water mol-ecules and two hexa-methyl-ene-tetra-mine (HMT) mol-ecules to generate distorted trans-CoN4O2 octa-hedra. The discrete complexes are each connected by two HMT solvate mol-ecules into chains via strong O-H⋯N hydrogen bonds. These chains are further linked by additional O-H⋯N and C-H⋯N and C-H⋯S hydrogen bonds into a three-dimensional network. Within this network, channels are formed that propagate along the c-axis direction and in which additional aceto-nitrile solvent mol-ecules are embedded, which are hydrogen bonded to the network. The CN stretching vibration of the thio-cyanate ion occurs at 2062 cm-1, which is in agreement with the presence of N-bonded anionic ligands. XRPD investigations prove the formation of the title compound as the major phase accompanied by a small amount of a second unknown phase.

Synthesis, crystal structure and thermal properties of poly[bis-[μ-3-(amino-meth-yl)pyridine-κ2 N:N']bis(thio-cyanato-κN)manganese(II)]

The reaction of Mn(NCS)2 with a stoichiometric amount of 3-(amino-meth-yl)pyridine in ethanol led to the formation of the title compound, [Mn(NCS)2(C6H8N2)2] n , which is isotypic to its Zn, Co and Cd analogues. The manganese cation is located on a centre of inversion and is octa-hedrally coordinated in an all-trans configuration by two terminal N-bonded thio-cyanate anions as well as four 3-(amino-meth-yl)pyridine co-ligands, of which two coordinate with the pyridine N atom and two with the amino N atom. The 3-(amino-meth-yl)pyridine co-ligands connect the MnII cations into layers extending parallel to (10). These layers are further connected into a three-dimensional network by relatively strong inter-molecular N-H⋯S hydrogen bonding. Comparison of the experimental X-ray powder diffraction pattern with the calculated pattern on the basis of single-crystal data proves the formation of a pure crystalline phase. IR measurements showed the CN stretching vibration of the thio-cyanate anions at 2067 cm-1, which is in agreement with the presence of terminally N-bonded anionic ligands. TG-DTA measurements revealed that the title compound decomposes at about 500 K.

Synthesis, crystal structure and thermal properties of poly[bis-[μ2-3-(amino-meth-yl)pyridine]-bis-(thio-cyanato)-cobalt(II)]

The reaction of Co(NCS)2 with 3-(amino-meth-yl)pyridine as coligand leads to the formation of crystals of the title compound, [Co(NCS)2(C6H8N2)2] n , that were characterized by single-crystal X-ray analysis. In the crystal structure, the CoII cations are octa-hedrally coordinated by two terminal N-bonded thio-cyanate anions as well as two pyridine and two amino N atoms of four symmetry-equivalent 3-(amino-meth-yl)pyridine coligands with all pairs of equivalent atoms in a trans position. The CoII cations are linked by the 3-(amino-meth-yl)pyridine coligands into layers parallel to the ac plane. These layers are further linked by inter-molecular N-H⋯S hydrogen bonding into a three-dimensional network. The purity of the title compound was determined by X-ray powder diffraction and its thermal behavior was investigated by differential scanning calorimetry and thermogravimetry.

Crystal structure of bis-(tetra-methyl-thio-urea-κS)bis-(thio-cyanato-κN)nickel(II)

In the course of our investigations regarding transition-metal thio-cyanates with thio-urea derivatives, the title compound, [Ni(NCS)2(C5H12N2S)2], was obtained. The asymmetric unit consists of one thio-cyanate anion and one tetra-methyl-thio-urea mol-ecule on general positions, as well as one NiII cation that is located on a twofold rotational axis. In this compound, discrete complexes are formed in which the NiII cations are surrounded by two trans-N-bonding thio-cyanate anions as well as two trans-S-bonding tetra-methyl-thio-urea mol-ecules within a distorted square-planar coordination geometry. The discrete complexes are linked by pairs of weak C-H⋯S hydrogen bonds between the thio-cyanate S and one of the tetra-methyl-thio-urea methyl hydrogen atoms into chains along the crystallographic a- and c-axis directions, which are combined into layers parallel to the ac plane. X-ray powder diffraction proves that a pure crystalline phase was obtained and measurements using thermogravimetry and differential thermoanalysis reveal that the compound decomposes at about 408 K, where all tetra-methyl-thio-urea mol-ecules are lost.

Thermodynamically metastable chain and stable layered Co(NCS)2 coordination polymers: thermodynamic relations and magnetic properties

Reaction of Co(NCS)2 with 4-bromopyridine leads to the formation of discrete complexes with the composition Co(NCS)2(4-bromopyridine)4·(CH3CN)0.67 (1), Co(NCS)2(4-bromopyridine)2(H2O)2 (2), Co(NCS)2(4-bromopyridine)2(CH3OH)2 (3) and Co(NCS)2(4-bromopyridine)2(CH3CN)2 (4). Upon heating compounds 2 and 4 transform into a crystalline product with the composition Co(NCS)2(4-bromopyridine)2 (5-I) that also can easily be obtained from solution. In this compound, the Co cations are linked by single μ-1,3-bridging thiocyanate anions into layers. Thermal decomposition of 3 leads to a second isomer (5-II), which is thermodynamically metastable and can also be synthesized from solution under kinetic control. In contrast to 5-I, the Co cations are linked by pairs of anionic ligands into linear chains. The magnetic exchange is very weak in 5-I, but much stronger and ferromagnetic along the linear chains in 5-II. AF ordering in 5-II is reached at 3.05 K, and magnetic relaxation is observed at the metamagnetic transition with an Arrhenius barrier of 17.1(3) cm-1. Ab initio computational studies reveal a different type of magnetic anisotropy to be present in the two crystallographically - independent Co centers in 5-II.

Crystal structure of bis-(N,N'-di-methyl-thio-urea-κS)bis-(thio-cyanato-κN)cobalt(II)

During systematic investigations on the synthesis of coordination polymers with Co(NCS)2 involving different thio-urea derivatives as coligands, crystals of the title compound Co(NCS)2(N,N'-di-methyl-thio-urea)2, or [Co(C3H8N2S)2(NCS)2], were obtained. These crystals were non-merohedric twins and therefore, a twin refinement using data in HKLF-5 format was performed. In the crystal structure of this compound, the CoII cations are coordinated by two N-terminally bonded thio-cyanate anions as well as two S-bonding N,N'-di-methyl-thio-urea mol-ecules, forming two crystallographically independent discrete complexes each with a strongly distorted tetra-hedral geometry. An intricate network of inter-molecular N-H⋯S and C-H⋯S hydrogen bonds can be found between the complexes. The thermogravimetric curve of the title compound shows two discrete steps in which all coligand mol-ecules have been emitted, which is also accompanied by partial decomposition of the cobalt thio-cyanate. If the measurement is stopped after the first mass loss, only broad reflections of CoS can be found in the XRPD pattern of the residue, which proves that this compound decomposes completely upon heating. However, at lower temperatures an endothermic signal can be found in the DTA and DSC curve, which corresponds to melting, as proven by thermomicroscopy.

Crystal structure of bis-(tetra-methyl-thio-urea-κS)bis(thio-cyanato-κN)cobalt(II)

In the course of systematic investigations on the synthesis of Co(NCS)2 coordination compounds with different thio-urea ligands, the title compound, [Co(NCS)2(C5H12N2S)2], was obtained. In this compound the CoII cations are coordinated by two crystallographically independent N-bonded thio-cyanate anions and two tetra-methyl-thio-urea ligands into discrete complexes that are located in general positions and show a strongly distorted tetra-hedral geometry. Inter-molecular C-H⋯S hydrogen bonds of different strength can be observed between the discrete complexes, which are connected by pairs of hydrogen bonds into zigzag-like chains that elongate in the b-axis direction. These chains are additionally linked by strong C-H⋯S hydrogen bonds along the a-axis direction, resulting in the formation of layers that are parallel to the ab plane. There is also one weak intra-molecular C-H⋯S hydrogen bond between two neighbouring thio-urea ligands within the complexes. Comparison of the experimental PXRD pattern with that calculated from the single-crystal data prove that a pure phase has been obtained. Thermoanalytical investigations reveal that this compound melts at 364 K and decomposes upon further heating.

Influence of the Coligand onto the Magnetic Anisotropy and the Magnetic Behavior of One-Dimensional Coordination Polymers

Reaction of Co(NCS)₂ with different coligands leads to the formation of three compounds with the general composition [Co(NCS)₂(L)₂]_n (L = aniline (1), morpholine (2), and ethylenethiourea (3)). In all of these compounds the cobalt(II) cations are octahedrally coordinated by two trans thiocyanate N and S atoms and the apical donor atoms of the coligands and are linked into linear chains by pairs of anionic ligands. The magnetic behavior was investigated by a combination of static and dynamic susceptibility as well as specific-heat measurements, computational studies, and THz-EPR spectroscopy. All compounds show antiferromagnetic ordering as observed for similar compounds with pyridine derivatives as coligands. In contrast to the latter, for 1-3 significantly higher critical temperatures and no magnetic single-chain relaxations are observed, which can be traced back to stronger interchain interactions and a drastic change in the magnetic anisotropy of the metal centers. These results are discussed and compared with those of the pyridine-based compounds, which provides important insights into the parameters that govern the magnetic behavior of such one-dimensional coordination polymers.

Crystal structures and Hirshfeld surface analysis of trans-bis-(thio-cyanato-κN)bis-{2,4,6-trimethyl-N-[(pyridin-2-yl)methyl-idene]aniline-κ2 N,N'}manganese(II) and trans-bis-(thio-cyanato-κN)bis-{2,4,6-trimethyl-N-[(pyridin-2-yl)methyl-idene]aniline-κ 2 N,N'}nickel(II))

Two new mononuclear metal complexes involving the bidentate Schiff base ligand 2,4,6-trimethyl-N-[(pyridin-2-yl)methyl-idene]aniline (C15H16N2 or PM-TMA), [Mn(NCS)2(PM-TMA)2] (I) and [Ni(NCS)2(PM-TMA)2] (II), were synthesized and their structures determined by single-crystal X-ray diffraction. Although the title compounds crystallize in different crystal systems [triclinic for (I) and monoclinic for (II)], both asymmetric units consist of one-half of the complex mol-ecule, i.e. one metal(II) cation, one PM-TMA ligand, and one N-bound thio-cyanate anion. In both complexes, the metal(II) cation is located on a centre of inversion and adopts a distorted octa-hedral coordination environment defined by four N atoms from two symmetry-related PM-TMA ligands in the equatorial plane and two N atoms from two symmetry-related NCS- anions in a trans axial arrangement. The tri-methyl-benzene and pyridine rings of the PM-TMA ligand are oriented at dihedral angles of 74.18 (7) and 77.70 (12)° for (I) and (II), respectively. The subtle change in size of the central metal cations leads to a different crystal packing arrangement for (I) and (II) that is dominated by weak C-H⋯S, C-H⋯π, and π-π inter-actions. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to qu-antify these inter-molecular contacts, and indicate that the most significant contacts in packing are H⋯H [48.1% for (I) and 54.9% for (II)], followed by H⋯C/C⋯H [24.1% for (I) and 15.7% for (II)], and H⋯S/S⋯H [21.1% for (I) and 21.1% for (II)].

Octanuclear nickel phosphonate core forming extended and molecular structures

Three new nickel(ii) phosphonate complexes {[Na₂Ni₈(L)₆]·nSolv}_m (L = SAA³⁻ (1), BSAA³⁻ (2), NAA³⁻ (3); Solv = H₂O, MeOH; m = ∞ (1, 2), 1 (3)) possessing a new octanuclear {Ni₈} phosphonate core were obtained and studied in detail.

Impact of the synthetic approach on the magnetic properties and homogeneity of mixed crystals of tunable layered ferromagnetic coordination polymers

Different synthetic routes were applied to synthesize mixed crystals of [Co_xNi_1−x(NCS)₂(4-tert-butylpyridine)₂]_n that finally results in homogeneous samples for which the critical temperature can be tuned as function of the Co : Ni ratio.

Thermodynamically stable and metastable coordination polymers synthesized from solution and the solid state

Different Fe(ii) and Cd(ii) thiocyanate coordination compounds with unusual topology including isomeric modifications were synthesized with 4-picoline and investigated in regard to their thermodynamic relations.

New isomeric Ni(NCS)2 coordination compounds: crystal structures, magnetic properties as well as ex situ and in situ investigations on their synthesis and transition behaviour

Some stable and metastable isomeric Ni(NCS)₂ chain compounds were synthesized and structurally characterized and investigated for their transformation behavior and their magnetic properties using a variety of methods.

Structural diversity in Cd(NCS)2-3-cyanopyridine coordination compounds: synthesis, crystal structures and thermal properties

Five new compounds with the compositions [Cd(NCS)2(3-cyanopyridine)2] n  · 3-cyanopyridine (1), [Cd(NCS)2(3-cyanopyridine)2] n  · 1/3 3-cyanopyridine (2), [Cd(NCS)2(3-cyanopyridine)2] n (3), {[Cd(NCS)2]2(3-cyanopyridine)3} n (4), and {[Cd(NCS)2]3(3-cyanopyridine)4} n (5) have been obtained by the reaction of Cd(NCS)2 with 3-cyanopyridine in different solvents. While large amounts of compounds 1–4 could be prepared as powders, only a few single crystals of 5 were accidently obtained. Thermoanalytical investigations have shown that 4 could also be obtained by annealing of 1 or 2 and that under slightly different conditions 5 could be obtained as part of a mixture with 4. The crystal structures of all compounds can be divided in two sets of compounds. Compounds 1, 2 and 3 consist of chains in which the Cd cations show three different coordination environments and in which the coligands are only terminally bonded. In the structures of 4 and 5 similar chains are observed, which are connected into layers via some of the 3-cyanopyridine coligands.

Creation and stabilisation of tuneable open metal sites in thiocyanato-bridged heterometallic coordination polymers to be used as heterogeneous catalysts

A series of thiocyanato-bridged heterometallic coordination polymers with a 3D reticular network have been synthesised by the reaction of [Pt^IV(SCN)₆]^2- with M^II ions to form {M^II[Pt^IV(SCN)₆]}_n and {[M^II(CH₃OH)₂][Pt^IV(SCN)₆]}_n (M^II = Mn^II, Fe^II, Co^II, Ni^II or Cu^II) in water and methanol, respectively. Single-crystal X-ray analyses revealed the absence of open metal sites in {M^II[Pt^IV(SCN)₆]}_ns and the formation of potential open metal sites at the M^II ions of {[M^II(CH₃OH)₂][Pt^IV(SCN)₆]}_ns by the coordination of methanol. One of the two coordinating methanol molecules in {[Co^II(CH₃OH)₂][Pt^IV(SCN)₆]}_n was replaced with pyridine to stabilise the open metal sites, because the methanol molecules are too labile to maintain open metal sites in water. The heterogeneous catalysis of coordination polymers with and without open metal sites was examined for organophosphate hydrolysis and photocatalytic water oxidation to clarify the requisites for heterogeneous catalysts.

How to link theory and experiment for single-chain magnets beyond the Ising model: magnetic properties modeled from ab initio calculations of molecular fragments

Magnetic properties of coordination polymers like single-chain magnets (SCMs) are based on magnetic domains, which are formed due to magnetic exchange between neighboring anisotropic spin centers. However, the computational restrictions imposed by the high level of theory needed for an adequate ab initio quantum mechanical treatment on the basis of multi-reference methods for these systems limit the feasibility of such calculations to mononuclear fragments as appropriate structural cutouts for the metal centers along the chains. Hence, results from such calculations describe single-ion properties and cannot be directly correlated with experimental data representing magnetic domains. We present a theoretical approach based on n-membered Ising-spin rings with n = 3-12, which allows us to simulate magnetic domains and to derive important magnetic properties for SCM compounds. Magnetic exchange, which is not provided by calculations of mononuclear fragments, is obtained by fitting the theoretical magnetic susceptibility against experimental data. The presented approach is tested for cobalt(ii)-based SCMs with three types of repeating sequences, which differ in nuclearity and symmetry. The magnetic parameters derived using the presented approach were found to be in good agreement with the experimental data. Moreover, the energy spectra obtained for the three test cases using the presented approach are characteristic of a deviation of the individual systems from the ideal Ising behavior. An extrapolation technique towards larger systems (n > 12) is presented which can provide information on the statistical mean length of the magnetic domains in the three investigated SCM compounds.

Crystal structure, synthesis and thermal properties of tetra-kis-(4-benzoyl-pyridine-κN)bis-(iso-thio-cyanato-κN)iron(II)

The asymmetric unit of the title compound, [Fe(NCS)2(C12H9NO)4], consists of an FeII ion that is located on a centre of inversion, as well as two 4-benzoyl-pyridine ligands and one thio-cyanate anion in general positions. The FeII ions are coordinated by two N-terminal-bonded thio-cyanate anions and four 4-benzoyl-pyridine ligands into discrete complexes with a slightly distorted octa-hedral geometry. These complexes are further linked by weak C-H⋯O hydrogen bonds into chains running along the c-axis direction. Upon heating, this complex loses half of the 4-benzoyl-pyridine ligands and transforms into a compound with the composition Fe(NCS)2(4-benzoyl-pyridine)2, that might be isotypic to the corresponding MnII compound and for which the structure is unknown.

Crystal structure of bis(4-benzoyl-pyridine-κN)bis(methanol-κO)bis(thio-cyanato-κN)nickel(II) methanol monosolvate

The asymmetric unit of the title compound, [Ni(NCS)2(C12H9NO)2(CH3OH)2]·CH3OH, comprises one NiII cation, two thio-cyanate anions, two 4-benzoyl-pyridine coligands, two coordinating, as well as one non-coordinating methanol mol-ecule. The NiII cation is coordinated by two terminally N-bonded thio-cyanate anions, the N atoms of two 4-benzoyl-pyridine coligands and the O atoms of two methanol ligands within a slightly distorted octa-hedron. Individual complexes are linked by inter-molecular O-H⋯S hydrogen bonding into chains parallel to [010] that are further connected into layers parallel to (10) by C-H⋯S hydrogen bonds. Additional C-H⋯O hydrogen-bonding inter-actions lead to the formation of a three-dimensional network that limits channels extending parallel to [010] in which the non-coordinating methanol mol-ecules are located. They are hydrogen-bonded to the coordinating methanol mol-ecules. X-ray powder diffraction revealed that the compound could not be prepared as a pure phase.

Formation of di- and polynuclear Mn(II) thiocyanate pyrazole complexes in solution and in the solid state

Reaction of Mn(NCS)2 with pyrazole leads to the formation of three compounds with the compositions Mn(NCS)2(pyrazole)4 (1), [Mn(NCS)2]2(pyrazole)6 (2) and Mn(NCS)2(pyrazole)2 (3). Compound 1, already reported in the literature, consists of discrete complexes, in which the Mn(II) cations are octahedrally coordinated by four pyrazole ligands and two terminally N-bonded thiocyanate anions. In compound 2 each of the two Mn(II) cations are coordinated octahedrally by three pyrazole ligands and one terminal as well as two bridging thiocyanate anions, which link the metal cations into dimers. In compound 3 also octahedrally coordinated Mn(II) cations are present but they are linked into chains via centrosymmetric pairs of μ-1,3-bridging thiocyanate anions. Upon heating compound 1 loses the pyrazole co-ligands stepwise and is transformed into the chain compound 3 via the dimer 2 that is formed as an intermediate. Magnetic measurements on compounds 2 and 3 reveal dominating antiferromagnetic interactions, as already observed for 1D Mn(NCS)2 coordination compounds with pyridine based co-ligands.

Synthesis, crystal structure and properties of Cd(NCS)2 coordination compounds with two different Cd coordination modes

Reaction of Cd(NCS)2 with 4-methoxypyridine leads to the formation of four new compounds, of which one crystallizes in two different polymorphs. In Cd(NCS)2(4-methoxypyridine)4·(4-methoxypyridine)2 (1) and Cd(NCS)2(4-methoxypyridine)4 (2-I and 2-II) discrete complexes are found, in which the Cd cations are octahedrally coordinated by four 4-methoxypyridine co-ligands and two terminally N-bonded thiocyanate anions. For the polymorphs 2-I and 2-II no single crystals are available and therefore, the corresponding Mn(II) compound (2-I-Mn) was prepared, which is isotypic to 2-I, as proven by a Rietveld refinement. The crystal structure of 2-II was solved and refined from XRPD data. In [Cd(NCS)2(4-methoxypyridine)2] n (3), the Cd cations are also octahedrally coordinated but linked into linear chains by pairs of thiocyanate anions with all ligands in trans-position. {[Cd(NCS)2]3(4-methoxypyridine)5} n (4) also consists of chains but two different Cd coordination modes are observed. Two of the three crystallographically independent Cd cations show an octahedral coordination with a trans- or cis-arrangement of the N and S atoms of the anionic ligands, whereas the third one is in a distorted square-pyramidal coordination, with cis-coordination of the thiocyanate N and S atoms. Measurements using simultaneous thermogravimetry and differential scanning calorimetry of 2-I and 2-II show different heating rate dependent mass steps, in which the co-ligands are removed. In some of the residues obtained after the respective TG steps compound 3 was detected but no phase pure samples could be obtained.

Structures, Thermodynamic Relations, and Magnetism of Stable and Metastable Ni(NCS)2 Coordination Polymers

Reaction of Ni(NCS)₂ with 4-aminopyridine in different solvents leads to the formation of compounds with the compositions Ni(NCS)₂(4-aminopyridine)₄ (1), Ni(NCS)₂(4-aminopyridine)₂(H₂O)₂ (2), [Ni(NCS)₂(4-aminopyridine)₃(MeCN)]·MeCN (3), and [Ni(NCS)₂(4-aminopyridine)₂] _n (5-LT). Compounds 1, 2, and 3 form discrete complexes, with octahedral metal coordination. In 5-LT the Ni cations are linked by single thiocyanate anions into chains, which are further connected into layers by half of the 4-aminopyridine coligands. Upon heating, 1 transforms into an isomer of 5-LT with a 1D structure (5-HT), that on further heating forms a more condensed chain compound [Ni(NCS)₂(4-aminopyridine)] _n (6) that shows a very unusual chain topology. If 3 is heated, a further compound with the composition Ni(NCS)₂(4-aminopyridine)₃ (4) is formed, which presumably is a dimer and which on further heating transforms into 6 via 5-HT as intermediate. Further investigations reveal that 5-LT and 5-HT are related by enantiotropism, with 5-LT being the thermodynamic stable form at room-temperature. Magnetic and specific heat measurements reveal ferromagnetic exchange through thiocyanate bridges and magnetic ordering due to antiferromagnetic interchain interactions at 5.30(5) K and 8.2(2) K for 5-LT and 6, respectively. Consecutive metamagnetic transitions in the spin ladder compound 6 are due to dipolar interchain interactions. A convenient formula for susceptibility of the ferromagnetic Heisenberg chain of isotropic spins S = 1 is proposed, based on numerical DMRG calculations, and used to determine exchange constants.

Anion-dependent self-assembly of copper coordination polymers based on pyrazole-3,5-dicarboxylate and 1,2-di(4-pyridyl)ethylene

By utilizing a pyrazole-3,5-dicarboxylic acid (H₃pzdc) and flexible 1,2-di(4-pyridyl)ethylene (dpe) with various copper(ii) salts under the same solvothermal synthetic conditions, six novel coordination polymers, namely, {[Cu₂(pzdc)(dpe)₂]X}_n (X = NO₃^- (1), ClO₄^- (2), BF₄^- (3), SCN^- (4)), {[Cu(ii)₄Cu(i)₄(pzdc)₄(dpe)₆](H₂O)₄}_2n (5), and {[Cu₅(HPO₄)₂ (pzdc)₂(dpe)₃](H₂O)₅}_n (6) were obtained. The structural diversity of compounds 1-6 depends on the starting Cu(ii) salts. Compounds 1-4 are isostructural and exhibit a 3D porous cationic pillar-layered coordination framework with lattice monoanions incorporated into the channels of the framework. When using copper(ii) sulfate as a reagent, a neutral mixed-valence Cu(i,ii) 2D + 2D → 2D parallel interpenetrated layer of 5 was obtained. In the case of a phosphate trianion, compound 6 shows a 3D coordination framework which contains μ₄-HPO₄^2- linking between Cu(ii) centers. The anion-exchange properties of 1-4 were studied. Interestingly, compounds 1-4 exhibit the irreversible chemisorption of the thiocyanate anion instead of anion exchange without the destruction of their structural framework as confirmed by PXRD, IR, UV-Vis, and AA spectroscopy. Moreover, the anion-induced structural transformation of 1-4 was observed when exchanging with an azide anion. The luminescent properties of 1-6 and exchanged products were also investigated.

Cd(II) and Zn(II) thiocyanate coordination compounds with 3-ethylpyridine: synthesis, crystal structures and properties

Reaction of Cd(NCS)2 and Zn(NCS)2 with 3-ethylpyridine leads to the formation of compounds of compositions M(NCS)2(3-ethylpyridine)4 (M=Cd, 1-Cd; Zn, 1-Zn) and M(NCS)2(3-ethylpyridine)2 (M=Cd, 2-Cd; Zn, 2-Zn). 1-Cd and 1-Zn are isotypic and form discrete complexes in which the metal cations are octahedrally coordinated by two trans-coordinating N-bonded thiocyanate anions and four 3-ethylpyridine co-ligands. In 2-Cd the cations are also octahedrally coordinated but linked into chains by pairs of μ-1,3-bridging anionic ligands. 2-Zn is built up of discrete complexes, in which the Zn cation is tetrahedrally coordinated by two N-bonded thiocyanate anions and two 3-ethylpyridine co-ligands. Compounds 1-Cd, 2-Cd and 2-Zn can be prepared in a pure state, whereas 1-Zn is unstable and transforms on storage into 2-Zn. If 1-Cd and 1-Zn are heated, a transformation into 2-Cd, respectively 2-Zn is observed. Luminescence measurements reveal that 1-Cd, 2-Cd and 2-Zn emit light in the blue spectral range with maxima at, respectively, 21724, 21654 and 22055 cm−1, assigned to ligand-based luminescence.

Crystal structures of bis-[4-(di-methyl-amino)-pyridinium] tetra-kis-(thio-cyanato-κN)manganate(II) and tris-[4-(di-methyl-amino)-pyridinium] penta-kis(thio-cyanato-κN)manganate(II)

The crystal structures of the title salts, (C7H11N2)2[Mn(NCS)4] (1) and (C7H11N2)3[Mn(NCS)5] (2), consist of manganese(II) cations that are tetra-hedrally (1) or trigonal-bipyramidally (2) coordinated to four or five terminal N-bonded thio-cyanate ligands, respectively, into discrete anionic complexes. The negative charge is compensated by two (1) or three (2) 4-(di-methyl-amino)-pyridinium cations, which are protonated at the pyridine N atom. The asymmetric unit of compound 1 consists of one anionic complex and two 4-(di-methyl-amino)-pyridinium cations, whereas that of compound 2 consists of two anionic complexes and six 4-(di-methyl-amino)-pyridinium cations, all of them located in general positions. These complexes are linked by N-H⋯S, C-H⋯S and C-H⋯N hydrogen-bonding inter-actions between the 4-(di-methyl-amino)-pyridinium cations and the thio-cyanate ligands into three-dimensional network structures.

Selective coordination of cyanate and thiocyanate in the end-on mode: synthesis, structures and properties of [NiII2L(μ1,1-NCO)]+ and [NiII2L(μ1,1-NCS)]+ (L2− = macrocyclic N6S2 ligand)

The complex [Ni₂L]²⁺ exhibits a pre-organized binding pocket, whose walls direct the coordination of pseudohalide ions via repulsive CH⋯π interactions.