In search of molecules displaying ferromagnetic exchange: multiple-decker Ni₁₂ and Ni₁₆ complexes from the use of pyridine-2-amidoxime

Abstract

The use of pyridine-2-amidoxime (pyaoxH) in Ni chemistry has provided access to a dodecanuclear complex and a hexadecanuclear Ni cluster, namely [Ni(pyaox)(pyaoxH)(MeOH)Cl]Cl·5MeOH (1·5MeOH) and [Ni(pyaox)(pyaoxH)(MeOH)](SO)·10HO·26MeOH (2·10HO·26MeOH). Complex 1·5MeOH was isolated by the reaction of NiCl·6HO, pyaoxH and NaOMe in a 1 : 1 : 2 molar ratio in MeOH in 60% yield. Treatment of NiSO·6HO with pyaoxH and NEt in a 1 : 1 : 2 molar ratio in MeOH afforded 2·10HO·26MeOH in good yield (65%). The two compounds display a multi-decker configuration based on stacked Ni layers, {Ni(pyaox)(pyaoxH)} (x = 3, 1·5MeOH; x = 4, 2·10HO·26MeOH); each deck consists of two square planar and two octahedral Ni centres. The number of decks observed in 1·5MeOH and 2·10HO·26MeOH depends on the nature of the inorganic anion that is present in the reaction system, which provides elements of synthetic control towards new high nuclearity Ni species. 2·10HO·26MeOH is the first structurally characterized complex of any metal displaying a quadruple-decker configuration, being also the highest nuclearity metal cluster bearing pyaoxH and the highest nuclearity Ni cluster with any type of 2-pyridyl oxime. Each cluster cation displays ferromagnetic exchange between the octahedral Ni ions resulting in a spin ground state of S = 6 for 1 and S = 8 for 2. Magnetothermal studies have been performed and discussed for both clusters.

From 1D Coordination Polymers to Metal Organic Frameworks by the Use of 2-Pyridyl Oximes

“…These research efforts have resulted in a large number of new homo- and heterometallic new species with interesting structural features and magnetic properties, e.g., Ni 5 , Ni 12 , Ni 16 , Ni 2 Ln 2 , Ni 8 Ln 8 , Ni 2 Mn 2 , Mn 8 , etc. [ 83 , 84 , 85 , 86 , 87 , 88 , 89 ]. We recently decided to explore the ability of such ligands to favor the formation of MOFs, when combined with di- and tricarboxylic ligands, such as 1,4-benzenedicarboxylic and 1,3,5-benzenetricarboxylic acid [ 110 ].…”

“…We have developed an intense interest over the last years in the synthesis of metal clusters and SMMs by the use of 2-pyridyl oximes as bridging ligands. These research efforts have resulted in a large number of new homo-and heterometallic new species with interesting structural features and magnetic properties, e.g., Ni [83][84][85][86][87][88][89]. We recently decided to explore the ability of such ligands to favor the formation of MOFs, when combined with di-and tricarboxylic ligands, such as 1,4-benzenedicarboxylic and 1,3,5-benzenetricarboxylic acid [110].…”

“…Thus, it is essential that ligands with high bridging capability that have the potential to lead to species with unprecedented metal topologies and/or high nuclearity SBUs be introduced into this field; to this purpose, we decided to use 2-pyridyl oximes for the isolation and characterization of new MOFs and coordination polymers. 2-pyridyl oximes is a family of ligands that have been extensively used in metal cluster chemistry due to their ability to bridge a large number of metal ions and, often, promote ferromagnetic interactions between the metal centers [ 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 ]. Although the use of such ligands has led to significant breakthroughs in the areas of single-molecule and single-chain magnetism, they have never been employed for MOF synthesis [ 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 ].…”

Rare Nuclearities in Ni(II) Cluster Chemistry: An Unprecedented {Ni12} Nanosized Cage from the Use of N-Naphthalidene-2-Amino-5-Chlorobenzoic Acid

“…(7,8,9,11)] subunits by sharing the common Ni3 and Ni7 vertices, respectively. Finally, the nuclearity of complex 1 is the largest reported to date of a metal cluster bearing nacb 2− chelate, and it joins a relatively rare family of {Ni12} Werner-type compounds with a cage-like conformation [21][22][23][24].…”

“…An alternative description of the {Ni12} metal arrangement is that of a central {Ni7} subunit possessing a distorted disk-like topology [Ni (1,2,3,5,6,7,10)], which is attached to a {Ni3} triangular [Ni (3,4,12)] and a {Ni4} rhombus-shaped [Ni (7,8,9,11)] subunits by sharing the common Ni3 and Ni7 vertices, respectively. Finally, the nuclearity of complex 1 is the largest reported to date of a metal cluster bearing nacb 2− chelate, and it joins a relatively rare family of {Ni12} Werner-type compounds with a cage-like conformation [21][22][23][24].…”