Preparation, Properties, and Structures of Pentanuclear [{Ni₂L}₂(μ‐csalen)M]²⁺ Complexes (L = Macrocyclic N₆S₂ ­Donor Ligand)

Abstract

The dinuclear nickel complex [Ni2L(μ‐Cl)]+ (1), where L2– is a 24‐membered macrocyclic N6S2 ligand, reacts readily with 3‐formyl‐4‐hydroxy‐benzoic acid (Hfhba) to form the carboxylato‐bridged complex [Ni2L(μ‐fhba)]+ (2). Complex 2 undergoes a condensation reaction with ethylene diamine to produce a tetranuclear complex [{Ni2L}2(μ‐H2csalen)]2+ (3), in which two dinuclear {Ni2L} units are bridged via the deprotonated carboxylate functions of the csalen ligand N,N′‐bis(4‐carboxysalicylidene)‐1, 2‐diaminoethane. The same compound can also be prepared directly from 1 and H2csalen. The complexation of 3 with NiCl2·6H2O, Cu(OAc)2·H2O or Pd(OAc)2 provides pentanuclear complexes of the type [{Ni2L}2(μ‐csalen)M]2+ [M = Ni (4a), Cu (4b), Pd (4c)]. All complexes were isolated as perchlorate salts and studied by ESI‐MS, infrared, and UV/Vis spectroscopy. The tetraphenylborate salt of 4c was also characterized by X‐ray crystallography. The [(csalen)M] complex units act in all cases as quadridentate bridging ligands linking two bioctahedral {Ni2L} units via μ‐1, 3‐bridging carboxylate functions. The palladium complex 4c was found to catalyze Heck‐coupling reactions of various iodobenzenes with methyl acrylate and styrene.

Synthesis and Characterisation of Luminescent [CrIII2L(μ‐carboxylato)]3+ Complexes with High‐Spin S=3 Ground States (L=N6S2 donor ligand)

“…The doubly deprotonated form, L 2− , is an effective dinucleating ligand that readily forms bioctahedral complexes of the type [M 2 L( μ ‐L′)] + with various first‐row transition metal ions (M=Mn 2+ , Fe 2+ , Co 2+ , Co 3+ , Ni 2+ , Figure 1 ). [38] Several co‐ligands such as L′=Cl − , OH − , [39] HS − , [40] and RCO 2 − ,[ 41 , 42 , 43 , 44 , 45 , 46 ] to name just a few, can be accommodated between the divalent metal ions. Complexes of this kind offer the opportunity to investigate intramolecular magnetic super‐exchange interaction as a function of the electronic configuration of the metal ions and the type of the coligand.…”

Group 12 Metal Complexes of an 18-Membered N2O2S2 Macrocycle Incorporating Two Pyridines: First Examples of an Infinite Mercury(I) Complex and a Dumbbell-Shaped Heteronuclear Complex with a Macrocyclic Ligand

“…Macrocyclic complexes with a wide range of structures have been reported over the last four decades . The structural diversity of such complexes often arises from connection of the macrocyclic building blocks via metal centers or coligands using a variety of bridging arrangements. − As a result, discrete macrocyclic complexes involve not only 1:1 (metal:ligand) complexes with typical endocyclic complexation but also extended oligomeric analogues such as sandwich, club sandwich, double decker, cyclic oligomer, and dumbbell − shaped structures displaying unusual stoichiometries.…”

“…The formation of dumbbells has been achieved by employing two endocyclic complex units and one linker unit (Chart ). − Several macrocyclic dumbbells linked with organic coligands have been reported by both us and other groups . For example, a series of dumbbells of type [(LAg)–L′–(AgL)] in which two endocyclic silver­(I)–L complex units are interconnected by organic coligands of type L′ [L′ = 1,4-diazabicyclo[2.2.2]­octane (dabco), 4,4-bipyridine (bpy), or 1,4-bis­(4-pyridyl)­piperazine (bpp)] have been described .…”

Fifty Years of Inorganic Biomimetic Chemistry: From the Complexation of Single Metal Cations to Polynuclear Metal Complexes by Multidentate Thiolate Ligands

“…Additionally, the use of the Pd (II) complex as a catalyst in the Heck reaction was investigated. However, due to the sterical hindrance of the central metal, the activity of this catalyst was low in comparison to other Pd‐salen complexes [70] …”

“…(Right) [Ni 2 (L14 Me )L'] + complexes 20 and 21 with L' = ω-mercapto-carboxylato coligand with the linear configuration of the aryl bridge and the bent configuration of the alkyl bridge. [70,71] electron oxidation processes; namely Co (III) Co (II) /Co (II) Co (II) and Co (III) Co (III) /Co (III) Co (II) . The oxidized species were obtained by chemical oxidation by using mild oxidizing agents (I 2 to obtain the mixed valent [Co (II) Co (III) ] 2 + dications and Br 2 to obtain the fully oxidized [Co (III) 2 ] 3 + trication).…”