Synthesis, Crystal Structures and Properties of Polymorphic and Isomeric Nickel(II)thiocyanate Coordination Compounds with 3‐Bromopyridine as Coligand

Abstract

Reaction of different molar ratios of Ni(NCS)2 and 3‐bromopyridine in water, methanol or acetonitrile leads to the formation of two polymorphs of composition Ni(NCS)2(3‐bromopyridine)4 (1‐I and 1‐II), as well as Ni(NCS)2(3‐bromopyridine)2(H2O)2 (2), Ni(NCS)2(3‐Bromopyridine)2(CH3OH)2 (3), Ni(NCS)2(3‐bromopyridine)2 ⋅ CH3CN (4) and Ni(NCS)2(3‐bromopyridine)2 (5). Compounds 1‐I, 1‐II, 2 and 3 consist of discrete octahedral complexes with terminal N‐bonded anionic ligands. In compound 4 the Ni cations are cis‐cis‐trans coordinated and linked into corrugated chains by pairs of μ‐1,3‐bridging thiocyanate anions. Solvent mediated conversion experiments prove that form 1‐I represents the thermodynamically stable polymorph at room temperature. TG‐DTA measurements reveal that upon heating compounds 1‐I, 1‐II, 2 and 3 lose their coligands stepwise and transform into the new crystalline phase 5 that can also be obtained from solution if the reaction is performed in n‐butanol. If the acetonitrile solvate molecules are removed from compound 4, it also transforms into 5. DC magnetic measurements for compound 4 show a maximum, which is indicative for antiferromagnetic ordering, whereas for compound 5 no magnetic ordering is observed. For both compounds, the ferromagnetic exchange constants were determined.

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

“…Crystal Structure of the Chain Compounds 4 and 5. The crystal structure of 4 solved by Rietveld refinement (Figure S17) is isotypic to a previously reported nickel(II) compound, 87 as mentioned above, and is therefore only briefly described for the sake of comparison. However, it should be noted that a significant line broadening in the PXRD pattern is present, which could be modeled best as isotropic strain.…”

“…83−86 That is the nickel(II) compound [Ni(NCS) 2 (3-bromopyridine) 2 ] n , which contains octahedrally coordinated nickel(II) cations linked by pairs of μ-1,3-bridging thiocyanate anions into chains. 87 Starting from mononuclear precursors, we present here the synthesis of two related Co(NCS) 2 chain compounds with 3-bromopyridine as a coligand: one is isostructural to the nickel(II) compound, whereas the second shows an unprecedented chain structure with alternating 5-and 6-fold-coordinated cobalt(II) ions. This difference in the coordination number results in a nearly orthogonal orientation of the easy axis of magnetization at the cobalt(II) ions along the chain and, consequently, non-Ising magnetic behavior.…”

“…Herein, we report the extension of our systematic study on the influence of variation of the coligand on the properties of Co­(NCS) 2 compounds toward 3-bromopyridine, a pyridine derivative with substitution in the meta position to the nitrogen-donor atom. For this ligand, compounds based on copper­(I), copper­(II), zinc­(II), cadmium­(II), and nickel­(II) have been reported in the literature, all of which are discrete complexes with one exception. − That is the nickel­(II) compound [Ni­(NCS) 2 (3-bromopyridine) 2 ] n , which contains octahedrally coordinated nickel­(II) cations linked by pairs of μ-1,3-bridging thiocyanate anions into chains . Starting from mononuclear precursors, we present here the synthesis of two related Co­(NCS) 2 chain compounds with 3-bromopyridine as a coligand: one is isostructural to the nickel­(II) compound, whereas the second shows an unprecedented chain structure with alternating 5- and 6-fold-coordinated cobalt­(II) ions.…”

Importance of non-covalent interactions in a nitrile anion metal-complex based on pyridine ligands: A theoretical and experimental approach

“…As a consequence of their ability to link metal ions in a variety of different ways, pseudohalide and polynitrile anions, either functioning alone or in combination with neutral co-ligands, provide opportunities for the generation of molecular architectures with varying dimensions and topologies. [1][2][3][4][5][6][7][8] For instance, due to the nature of their metal-ligand interactions, complex magnetic behaviors can arise in these systems. 9 Furthermore, the chemical richness of the nitrile anionic ligands allows the emergence of other interesting properties.…”

Crystal Packing Studies, Thermal Properties and Hirshfeld Surface Analysis in the Zn(II) Complex of 3-Aminopyridine with Thiocyanate as Co-Ligand

“…The coordination chemistry of thiocyanate ions is still a subject of intense scientific interest due to their diverse coordination modes (terminal and bridging) which eventually results in several structures with varying topologies and potential optical, photoluminescent and magnetic applications [3] [5] [20].…”