[Co₅Tp*₄(Me₂bta)₆]: A Highly Symmetrical Pentanuclear Kuratowski Complex Featuring Tris(pyrazolyl)borate and Benzotriazolate Ligands

Abstract

The pentanuclear Co(II) complex [Co5Tp*4(Me2bta)6] containing N-donor ligands (5,6-dimethyl benzotriazolate; Me2bta6) and N-donor capping ligands (tris(3,5-dimethyl-1-pyrazolyl)borate; Tp*) was prepared by a simple and efficient ligand exchange reaction from [Co5Cl4(Me2bta)6] and tetra-n-butyl ammonium tris(3,5-dimethyl-1-pyrazolyl)borate. Compared to the precursor complex [Co5Cl4(Me2bta)6], which contains one Co(II) ion in octahedral and four Co(II) ions in tetrahedral coordination geometry, the title compound features all five Co(II) ions in an octahedral coordination environment while keeping a high complex symmetry. This results in modified properties including improved solubility and distinct magnetic behavior as compared to the precursor complex. The molecular structure and phase purity of the compound was verified by XRPD, UV-vis, ESI-MS, IR, and NMR measurements. Thermal stability of the compound was determined via TGA. The magnetic properties of here reported novel complex [Co5Tp*4(Me2bta)6] as well as its precursor [Co5Cl4(Me2bta)6] were examined in detail via ESR and SQUID measurements, which indicated weak anti-ferromagnetic exchange interactions between high-spin Co(II) centers at T < 20 and 50 K, respectively.

Paramagnetic Resonance of Cobalt(II) Trispyrazolylmethanes and Counterion Association

“…The scorpionates represent one of the most versatile ligand scaffolds ever developed. Since they were first reported in the late 1960s, − they have found utility in catalytic, molecular magnetic, and enzyme model systems. − They also presented some of the first examples of spin-crossover complexes, , a property that remains a topic of current research . Both trispyrazolylborate (Tp) and the related trispyrazolylmethane (Tpm) present three pyrazole nitrogens as donors, constrained to a facial arrangement.…”

Pentanuclear Thorium(IV) Coordination Cluster from the Use of Di(2-pyridyl) Ketone

“…The two equal edges of the tetrahedron faces (Th2···Th2′′′ = Th2···Th2′′, Th2′···Th2′′ = Th2′···Th2′′′) are 6.284(1) Å, and the third face (Th2···Th2′ = Th2′′···Th2′′′) is 6.763(1) Å. The S 4 symmetry and this type of distortion are often seen in this type of pentanuclear complexes, but higher and lower symmetries are also observed. The graph theoretical analysis has proven that the bonding topologies in the {M c M 4 t L′ 6 L 4 } units contain the nonplanar K 3,3 graph.…”

“…Compound 2 belongs to the family of complexes named “Kuratowski-type” compounds by the Volkmer group. , The name owes its roots to the Polish mathematician Kazimierz Kuratowski, who introduced the nonplanar K 3,3 graph to group theory in the 1930s. The general formula of such compounds is [M c M t 4 L′ 6 L 4 ] (M c = M t or M c ≠ M t ), where M c and M t are the same or different first-row transition metals, L′ is a ligand spanning one edge of the tetrahedron defined by the four M t metal ions (t = terminal) and bridging the M c metal ion (c = central) with two M t metal ions, and L is a terminal ligand bound to an M t ion.…”

Acenaphtho[1,2‐d][1,2,3]triazole and Its Kuratowski Complex: A π‐Extended Tecton for Supramolecular and Coordinative Self‐Assembly

“…A reference ligand, 5,6,7,8‐tetrahydro‐1 H ‐naphtho[2,3‐ d ][1,2,3]triazole (Cybta‐H) was prepared by Pd‐catalyzed hydrogenation of 2,3‐naphtalenediamine 7 , followed by reaction with sodium nitrite. Kuratowski‐type complexes [Zn 5 Cl 4 (Dibanta) 6 ], and [Zn 5 Cl 4 (Cybta) 6 ], were obtained using slightly modified literature procedures,[ 28 , 29 ] by treating zinc chloride with the corresponding triazole ligand, in the presence of 2,6‐lutidine as a base at room temperature, followed by recrystallization.…”