Coordination Chemistry of an Unsymmetrical Naphthyridine‐Based Tetradentate Ligand toward Various Transition‐Metal Ions

Abstract

An unsymmetrical ligand, 2‐(2‐pyridinyl)‐7‐(pyrazol‐1‐yl)‐1,8‐naphthyridine (L5) was prepared for the construction of a series of dinuclear complexes. Treatment of L5 with [Ru2(µ‐OAc)4Cl] followed by anion metathesis afforded [(L5)(µ‐OAc)3Ru2](PF6) (3). Reaction of L5 with 2 equiv. of Ni(OAc)2 provided [Ni4(L5)2(µ‐OH)4(CF3COO)2](CF3COO)2 (5). Reaction of [Re2(CO)8(CH3CN)2] with L5 in a refluxing chlorobenzene solution gave a mixture of dirhenium (6) and monorhenium (7) complexes. The monocobalt complex 8 was obtained from complexation of L5 with CoCl2. These new complexes were characterized by elemental analysis and spectroscopic techniques. The structures of complexes 3, 5 and 8 were further confirmed by X‐ray crystallography. Nickel complex 5 was evaluated as a catalyst for reduction reactions involving the conversion of ester functionalities into their corresponding alcohols.

Unsymmetrical Naphthyridine-Based Dicopper(I) Complexes: Synthesis, Stability, and Carbon–Hydrogen Bond Activations

“…Studies on bimetallic complexes in this laboratory have focused on binucleating ligands with the 1,8-naphthyridine backbone. − The naphthyridine backbone can be symmetrically ,− or unsymmetrically − functionalized with side arms at the 2- and 7- positions to provide a rigid pocket for two transition metals, and these side arms can be the same, as in the DPEN and DPFN ligands, or different, as in the DPEPN ligand (Figure ). Previous studies from our laboratory demonstrated that the DPEN and DPFN ligands readily afford dicopper­(I) complexes in which bridging ligands bind symmetrically between the two Cu­(I) centers, and a dicopper DPFN-alkynyl complex was shown to be a competent catalyst for the copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction. ,,− Such dicopper-alkynyl species are proposed intermediates in several catalytic processes, including the Glaser–Hay coupling and the CuAAC reaction, , where their role has been studied computationally. − …”

Selective Synthesis of a Series of Isostructural MIICuI Heterobimetallic Complexes Spontaneously Assembled by an Unsymmetrical Naphthyridine‐Based Ligand

“…Indeed, upon treatment with mixtures of different metals, symmetrical ligands are expected to yield a mixture of products rather than one well‐defined heterobimetallic complex . The few reported unsymmetrical naphthyridine‐based dinucleating ligands are associated with low‐yielding syntheses, similar coordination environments, and formation of homometallic complexes upon metalation …”

“…[23][24][25] Moreover,n aphthyridine-based bimetallicc omplexes have been shown to catalyzearange of reactions. [33] Here we report the selective synthesis of an isostructural series of heterobimetallic complexes that employs an unsymmetricaln aphthyridine-based ligand (Scheme 1). Indeed, upon treatment with mixtures of differentm etals, symmetrical ligandsa re expected to yield am ixture of products rather than one well-defined heterobimetallic complex.…”

“…[32] The few reported unsymmetrical naphthyridine-based dinucleating ligands are associated with low-yielding syntheses, similar coordination environments, and formation of homometallic complexes upon metalation. [33] Here we report the selective synthesis of an isostructural series of heterobimetallic complexes that employs an unsymmetricaln aphthyridine-based ligand (Scheme 1). This ligand system spontaneously assembles specific heterobimetallic complexes that combine Cu I with ad ivalent first-row transition-metal ion from the Mn-Zn series.…”

A one-pot reduction route to bimetallic manganese 1,8-naphthyridine complexes

“…However, there are a growing number of situations documented where this approach does not produce bimetallic products. [8][9][10][11][12][13] There are several alternative approaches, none of which are widely generalisable. Use of preformed bimetallic precursors is an established method, but is limited to precursors containing metal-metal bonds.…”