Thiocyanato Coordination Compounds Research Articles

Synthesis, structures, and properties of Mn(II) and Cd(II) thiocyanato coordination compounds with 2,5-dimethylpyrazine as co-ligand

AbstractReaction of manganese (II) thiocyanate with 2,5-dimethylpyrazine leads to the formation of three new coordination compounds of compositions Mn(NCS)2(2,5-dimethylpyrazine)2(H2O)2(1), Mn(NCS)2(H2O)2(MeOH)2-tris(2,5-dimethylpyrazine) solvate (2), and Mn(NCS)2(H2O)4-tetrakis(2,5-dimethylpyrazine) solvate (3) that were characterized by single crystal X-ray diffraction. In their crystal structures, the Mn(II) cations are sixfold coordinated by two terminally N-bonded thiocyanato anions and two water molecules as well as by two 2,5-dimethylpyrazine ligands (1), two ethanol (2), or two water molecules (3), within slightly distorted octahedra. In compounds2and3, additional 2,5-dimethylpyrazine ligands are located in the cavities of the structures as solvate molecules. X-ray powder diffraction has shown that compounds1and2cannot be prepared as pure phases and that batches of compound3contain only minor traces of a contamination. Differential thermoanalysis and thermogravimetry have revealed that upon heating of compound3, an intermediate of composition Mn(NCS)2(2,5-dimethylpyrazine) (4) is formed, which cannot be obtained from solution. To mimic the structure of4, single crystals of a Cd compound of the same composition (5) were prepared from the liquid phase, and single crystal X-ray analysis has shown that it is isotypic to4.

Synthesis, Crystal Structures, and Thermal and Spectroscopic Properties of Thiocyanato Coordination Compounds with 3-Acetylpyridine as a Ligand

Abstract The reaction of transition metal thiocyanates with 3-acetylpyridine (3-Acpy) leads to the formation of compounds of compositions M(NCS)2(3-Acpy)4 (M1; M = Mn, Fe, Ni) and M(NCS)2(3- Acpy)2(H2O)2 (M2; M = Mn, Fe, Ni). Thermogravimetric investigations show that in the first step some of these compounds transform into the new coordination polymers M(NCS)2(3-Acpy)2 (M3 with M = Mn, Fe and Ni), that decompose into the new compounds M(NCS)2(3-Acpy) (M4 with M = Mn and Ni) in the second step. Unfortunately, the powder patterns of compounds M3 and M4 cannot be indexed, and there are strong indications that these compounds are contaminated with a small amount of the precursor or unknown crystalline phases. IR spectroscopic investigations indicate that in compounds M3 the metal cations are linked by μ-1,3-bridging thiocyanato anions into 1D or 2D coordination polymers that are further linked by the 3-Acpy ligands in compounds M4.

Synthesis, Structures, and Properties of Transition Metal Thiocyanato Coordination Compounds with 4‐(4‐Chlorobenzyl)pyridine as Ligand

AbstractReactions of transition metal thiocyanates with 4‐(4‐chlorobenzyl)pyridine (Clbp) lead to the formation of compounds of composition M(NCS)2(4‐(4‐chlorobenzyl)pyridine)4 (Mn‐1, Fe‐1/I, Fe‐1/II, Ni‐1, and Cd‐1) and M(NCS)2(4‐(4‐chlorobenzyl)pyridine)2 (Mn‐2, Ni‐2, and Cd‐2). In the crystal structures of compounds M‐1 the metal cations are octahedrally coordinated by two terminal N‐bonded thiocyanato anions and four Clbp ligands, whereas in compounds M‐2 the metal cations are linked by μ‐1, 3‐bridging anionic ligands. IR spectroscopic investigations show that the value of the asymmetric C–N stretching vibration depends on the coordination mode of the thiocyanato ligand and the nature of the metal cations. The thermal properties were investigated by simultaneous differential thermoanalysis and thermogravimetry as well as temperature dependent X‐ray powder diffraction. On heating compound Ni‐1 looses half of the Clbp ligands and transforms into Ni‐2. Clbp deficient intermediates were also detected on thermal decomposition of Mn‐1 and Fe‐1/I but the samples are of low crystallinity and therefore, their structures cannot be determined. Magnetic investigations reveal that Ni‐2 shows only Curie‐Weiss paramagnetism without any magnetic anomaly.

Synthesis, Structures, Polymorphism, and Magnetic Properties of Transition Metal Thiocyanato Coordination Compounds

Reaction of manganese, iron, and nickel thiocyanate with 4-ethylpyridine leads to the formation of single crystals of compounds with composition M(NCS)2(L)4 (1), M(NCS)2(L)2(H2O)2 (2-Mn), and M(NCS)2(L)2 (3) with M = Mn, Fe, and Ni and L = 4-ethylpyridine. For most compounds, different polymorphic modifications are observed, and their transition behavior and thermodynamic stability was investigated. Additionally, compounds of composition M(NCS)2(L)2 (M = Mn or Ni) were prepared from solution and by thermal decomposition of compounds 1 and 2, which lead to different stable and metastable modifications. The crystal structures of most compounds were determined by single crystal X-ray diffraction and some of them by Rietveld refinements. Compounds 1 and 2 consist of octahedrally coordinated discrete complexes with terminal N-bonded thiocyanato anions. In compounds 3, the metal cations are linked by pairs of μ-1,3-bridging thiocyanato anions into chains. Surprisingly, thermal decomposition of Ni(NCS)2(4-ethylpyridine)4 leads to the formation of a new compound of composition Ni(NCS)2(4-ethylpyridine) (4-Ni). Magnetic measurements reveal that 3-Mn/II and 3-Mn/III show antiferromagnetic ordering at TN = 21.5 and 23.9 K and that 4-Ni is a metamagnet with a critical field of 1.4 kOe at 2 K. All other compounds show Curie or Curie–Weiss behavior with no magnetic anomalies.

Synthesis, structures and magnetic properties of new Fe(II) and Co(II) thiocyanato coordination compounds with 2-chloropyrazine as Co-ligand

Investigations on the synthesis of coordination compounds based on Fe(NCS)2 and Co(NCS)2 with 2-chloropyrazine as ligand leads to the formation of five new compounds. Fe(NCS)2(2-chloropyrazine)4 (1-Fe), Co(NCS)2(2-chloropyrazine)4 (1-Co) and Fe(NCS)2(2-chloropyrazine)4·2-chloropyrazine solvate (2-Fe) consists of discrete complexes in which the metal cations are octahedrally coordinated and in which the thiocyanato anions are only terminal coordinated. On heating 1-Fe and 1-Co transform into new coordination polymers of composition [Fe(NCS)2(2-chloropyrazine)2]n (3-Fe) and [Co(NCS)2(2-chloropyrazine)2]n (3-Co) which are isotypic. No access to large and phase pure amounts of these compounds was found in solution but the structure of 3-Co was determined from a crystal obtained in one batch by accident. In the crystal structure of 3-Co and 3-Fe the metal(II) cations are coordinated by two N-bonded as well as two S-bonded thiocyanato anions and two 2-chloropyrazine ligands and are linked by μ-1,3-bridging anions into layers. Magnetic measurements of 1-Fe and 1-Co show only Curie- or Curie–Weiss paramagnetism, whereas for 3-Fe antiferromagnetic ordering and for 3-Co metamagnetic behavior is observed.

Structures and Magnetic Properties of Nickel Thiocyanato Coordination Compounds with 2‐Chloropyrazine as a Neutral Coligand

AbstractReaction of Ni(NCS)2 with 2‐chloropyrazine in different molar ratios and solvents at room temperature leads to five new coordination polymers. In the crystal structures of Ni(NCS)2(2‐chloropyrazine)4·2‐chloropyrazine solvate (1) and Ni(NCS)2(2‐chloropyrazine)4 (2) the nickel cations are octahedrally coordinated by two terminal N‐bonded thiocyanato anions and four 2‐chloropyrazine ligands into discrete complexes. In the crystal structures of the Ni(NCS)2(2‐chloropyrazine)2(CH3OH)2·(CH3OH)2 solvate (3) and Ni(NCS)2(2‐chloropyrazine)2(CH3OH)2 (4) each nickel(II) cation is coordinated by two terminal N‐bonded thiocyanato anions, two 2‐chloropyrazine ligands and two O‐bonded methanol molecules in a slightly distorted octahedron. On heating, compounds 1 and 2 transform into the ligand‐deficient 1:2 compound 5, which can also be crystallized from solution. In the crystal structure of [Ni(NCS)2(2‐chloropyrazine)2]n (5) each nickel(II) cation is coordinated by two N‐bonded and two S‐bonded thiocyanato anions as well as two 2‐chloropyrazine ligands. The nickel cations are linked into dimers by pairs of μ‐1,3‐bridging thiocyanato anions that are further linked into chains and finally into layers by single μ‐1,3‐bridging thiocyanato anions. Magnetic measurements of compound 1 and 2 show only Curie or Curie–Weiss paramagnetism, whereas in the ligand‐deficient compound 5 a metamagnetic transition is observed at a critical field of HC = 14 kOe. The results of the magnetic measurements are compared with those of related nickel compounds with different coligands.

Synthesis, structures and magnetic properties of Fe(ii) and Co(ii) thiocyanato coordination compounds: on the importance of the diamagnetic counterparts for structure determination

Reaction of Fe(NCS)2 and Co(NCS)2 with 2-methylpyrazine in different molar ratios and solvents at room temperature leads to the formation of five new coordination compounds of composition M(NCS)2(2-methylpyrazine)2(H2O)2 (M = Fe (1-Fe) , Co (1-Co)), Co(NCS)2(2-methylpyrazine)2(CH3OH)2 (2-Co) and Co(NCS)2(2-methylpyrazine)4·2-methylpyrazine solvate (3-Co). In all of these compounds, discrete complexes are found in which the metal cations are octahedrally coordinated by two terminal N-bonded thiocyanato anions and four N- or O-donor co-ligands. On heating compounds 1-3 in a thermobalance new coordination polymers of composition M(NCS)2(2-methylpyrazine)2 (M = Co (4-Co) , Fe (4-Fe)) are obtained in the first step, which transform into M(NCS)2(2-methylpyrazine) (M = Co (5-Co) , Fe (5-Fe)) in the second. Because of the low chalcophilicity of these cations, compounds 4 and 5 are not accessible from solution. Further investigations prove that 4-Co and 4-Fe obtained by thermal decomposition are of low crystallinity, might be isotypic and might consist of metal cations, in which the anionic ligands are only terminal N-bonded. In contrast, 5-Co and 5-Fe are of good crystallinity but their structure cannot be solved from X-ray powder data. However, a compound of the same composition (5-Cd) based on the more chalcophilic cadmium can easily be crystallized from solution and characterized by single crystal X-ray diffraction. This compound is isotypic to 5-Co and 5-Fe and therefore their structures were determined by Rietveld refinements. In their crystal structures the metal atoms are linked by μ-1,3-bridging thiocyanato anions into a 2D network. Magnetic measurements reveal that compounds 1-4 show only Curie-Weiss paramagnetism and that for 5-Fe antiferromagnetic ordering is observed. In contrast, 5-Co shows metamagnetic behavior with a very large critical field. Finally, it was shown that 4-Co and 4-Fe are hygroscopic and transform within minutes into the hydrates 1-Co and 1-Fe.

Investigations on the Structure Diversity and Thermal Degradation Behavior of CdII and ZnII Thiocyanato Coordination Compounds based on 3‐Acetylpyridine as Neutral Co‐Ligand

AbstractReaction of CdII and ZnII thiocyanate with 3‐acetylpyridine leads to the formation of the new CdII and ZnII coordination compounds [Cd(NCS)2(3‐acetylpyridine)4] (1A), [Cd(NCS)2(3‐acetylpyridine)2]n (1B), [Cd(NCS)2(3‐acetylpyridine)]n (1C) and [Zn(NCS)2(3‐acetylpyridine)2] (2A). Compound 1A consists of discrete complexes, in which the metal centers are octahedrally coordinated by four terminal bonded N‐donor co‐ligands and two terminal N‐bonded thiocyanato anions. In compound 2A the metal centers are only tetrahedrally coordinated by two terminal bonded N‐donor co‐ligands and two terminal N‐bonded thiocyanato anions. In compound 1B the CdII cations are octahedrally coordinated by two terminal bonded N‐donor co‐ligands and four thiocyanato anions. The metal centers are linked by μ‐1, 3 bridging thiocyanato anions into chains. In compound 1C the metal cations are octahedrally coordinated by two μ‐1, 5 bridging 3‐acetyl‐pyridine ligands and four μ‐1, 3 bridging thiocyanato anions building up a three‐dimensional coordination network. Investigations on the thermal degradation behavior of all compounds using simultaneous differential thermoanalysis and thermogravimetry as well as X‐ray powder diffraction and IR spectroscopy prove that on heating compound 2A decompose without the formation of 3‐acetylpyridine‐deficient intermediates. In contrast, for compound 1A a stepwise decomposition is observed, leading to the formation of the 3‐acetylpyridine‐deficient compound [Cd(NCS)2(3‐acetylpyridine)2]n (1B) which decomposes on further heating

New nickel(ii) thiocyanato coordination compounds: synthetic aspects, polymorphism, thermal reactivity and magnetic properties

Reaction of Ni(NCS)2 with bis(3-aminopropyl)amine (dpt) and pyridine (pyr) in water and molar ratios leads to the formation of the new polymorphic modifications [Ni(NCS)2(dpt)(pyr)] (1a and 1b). Slight variation of the reaction conditions results in the formation of the new nickel(II) thiocyanato coordination compounds {[Ni(dpt)2]2+·[(NCS)2]2−} (2), {[Ni(SCN)3(dpt)]−·[Ni(dpt)2·(NCS)]+·H2O} (3), {[Ni(μ-1,3-NCS)(dpt)(NCS)]2·[Ni(NCS)2(dpt)(H2O)]2·(H2O)4} (4) and [Ni(μ-1,3-NCS)(dpt)(NCS)]2 (5). All compounds were structurally characterized and investigated for their thermal, spectroscopic and magnetic properties. The polymorphic modifications 1a and 1b were additionally investigated by solvent mediated conversion experiments and DSC measurements for their thermodynamic stability, which show that form 1a represents the thermodynamically most stable over the whole temperature range. Investigations on the thermal degradation behavior of compounds 1a–4 show that only for compounds 1a and 4 ligand-deficient intermediates can be found whereas for all other compounds only complete decomposition is observed. Compound 4 decomposes to the literature known ligand-deficient compound {[Ni(μ-1,3-NCS)(dpt)(NCS)]2·[Ni(μ-1,3-NCS)(dpt)(NCS)]4} (Refcode MUYRAZ), whereas the intermediate of compound 1a could not be structurally characterized. On the basis of IR and Raman spectroscopic investigations it could be shown that in the intermediate of 1a bridging anions could be found and a tetrameric structure can be assumed. Magnetic measurements of compounds 1a–4 reveal only Curie and Curie-Weiss paramagnetism.

Synthesis, Crystal Structures, and Spectroscopic and Thermal Properties of New Cobalt Thiocyanato Coordination Compounds Based on 3-Methylpyridine as a Neutral Coligand

Reaction of cobalt(II) thiocyanate with 3-methylpyridine in water leads to the formation of the new ligand-rich cobalt(II) thiocyanato coordination compounds [bis(thiocyanato-N)-tetrakis(3-methylpyridine- N)cobalt(II)] (1) and [bis(thiocyanato-N)-bis(3-methylpyridine-N)-diaqua-cobalt(II)] (2). The crystal structures of 1 and 2 consist of discrete complexes in which the cobalt(II) cations are coordinated by two terminally N-bonded thiocyanato anions and four or two terminally bonded coligands, respectively, in a slightly distorted octahedral geometry. Investigations on the thermal degradation behavior of 1 and 2 using simultaneous differential thermoanalysis and thermogravimetry as well as X-ray powder diffraction and IR spectroscopy have proven that on heating a stepwise decomposition takes place, which leads to the formation of the new phase-pure ligand-deficient intermediate [bis(thiocyanato-N)-bis(3-methylpyridine-N)cobalt(II)] (3). The crystal structure of 3 also consists of discrete complexes, but the cobalt(II) cations are only tetrahedrally coordinated by two terminally N-bonded thiocyanato anions and two terminally bonded coligands. The structures and the thermal properties are discussed and compared with that of related transition metal thiocyanato coordination compounds.

Synthesis, Crystal Structures, and Spectroscopic and Thermal Properties of New Cobalt Thiocyanato Coordination Compounds Based on 3-Methylpyridine as a Neutral Coligand

Synthesis, Crystal Structures, and Spectroscopic and Thermal Properties of New Cobalt Thiocyanato Coordination Compounds Based on 3-Methylpyridine as a Neutral Coligand

Synthesis, Crystal Structures, and Thermal Properties of New Zinc(II) Thiocyanato Coordination Compounds

AbstractReaction of zinc(II) thiocyanate with pyrazine, pyrimidine, pyridazine, and pyridine leads to the formation of new zinc(II) thiocyanato coordination compounds. In bis(isothiocyanato‐N)‐bis(μ2‐pyrazine‐N,N) zinc(II) (1) and bis(isothiocyanato‐N)‐bis(μ2‐pyrimidine‐N,N) zinc(II) (2) the zinc atoms are coordinated by four nitrogen atoms of the diazine ligands and two nitrogen atoms of the isothiocyanato anions within slightly distorted octahedra. The zinc atoms are connected by the diazine ligands into layers, which are further linked by weak intermolecular S···S interactions in 1 and by weak intermolecular C–H···S hydrogen bonding in 2. In bis(isothiocyanato‐N)‐bis(pyridazine‐N) (3) discrete complexes are found, in which the zinc atoms are coordinated by two nitrogen atoms of the isothiocyanato ligands and two nitrogen atoms of the pyridazine ligands. The crystal structure of bis(isothiocyanato‐N)‐tetrakis(pyridine‐N) (4) is known and consists of discrete complexes, in which the zinc atoms are octahedrally coordinated by two thiocyanato anions and four pyridine molecules. Investigations using simultaneous differential thermoanalysis and thermogravimetry, X‐ray powder diffraction and IR spectroscopy prove that on heating, the ligand‐rich compounds 1, 2, and 3 decompose without the formation of ligand‐deficient intermediate phases. In contrast, compound 4 looses the pyridine ligands in two different steps, leading to the formation of the literature known ligand‐deficient compound bis(isothiocyanato‐N)‐bis(pyridine‐N) (5) as an intermediate. The crystal structure of compound 5 consists of tetrahedrally coordinated zinc atoms which are surrounded by two isothiocyanato anions and two pyridine ligands. The structures and the thermal reactivity are discussed and compared with this of related transition metal isothiocyanates with pyrazine, pyrimidine, pyridazine, and pyridine.