Dinuclear first-row transition metal complexes with a naphthyridine-based dinucleating ligand

Abstract

A series of dinuclear and tetranuclear first-row transition metal complexes were synthesized with the dinucleating ligand 2,7-bis(di(2-pyridyl)fluoromethyl)-1,8-naphthyridine (DPFN). The coordination pocket and rigidity of the DPFN ligand enforces pseudo-octahedral geometries about the metal centers that contain chloro, hydroxo, and aqua bridging ligands forming a "diamond" shaped configuration with metal-metal distances varying from 2.7826(5) to 3.2410(11) Å. Each metal center in the dinuclear complexes has an additional open coordination site that accommodates terminal ligands in a syn geometry of particular interest in catalyst design. The complexes are characterized by electronic spectroscopy, electrochemistry and potentiometric titration methods.

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

“…[35,36] They are also significantly shorter than those observed for symmetrical,b imetallic (M II ) 2 naphthyridine-basedc omplexes featuring two bridging chlorides (Co 2 :3 .238 ,N i 2 :3 .195 ,a nd Cu 2 :3 .241 ). [24] However, no cleart rend in M···Cu distances is observed across the series.…”

“…[11] Theu se of bifunctionall igandsw ith hard and soft binding sites, including those based on different P, Nand N,N-chelation, [12,13] has been as uccessful strategy in this regard; [14][15][16][17][18] however,t his approach often resultsi ns tructures that do not allow ready access to bridging coordination sites, [16][17][18][19][20] or is specific to certainm etal-metal combinations. [23][24][25] Moreover,n aphthyridine-based bimetallicc omplexes have been shown to catalyzearange of reactions. [22] The rigid naphthyridine core promotes ac lose interaction between two transition metals, and additional donor groups mayb ei ncorporated to enforce open binding sites for exploration of metal-metalc ooperativity in reactionc hemistry.…”

“…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. It features two moderately hard pyridine donors on one side, as in the symmetrical DPEN [23] and DPFN [24] environments, andasofter,e lectron-donatingd i-tertbutyl phosphine on the other.T he synthesis of this ligand was achievedi nt wo steps from 2-chloro-7-methyl-1,8-naphthyridine (Scheme 2). [33] Here we report the selective synthesis of an isostructural series of heterobimetallic complexes that employs an unsymmetricaln aphthyridine-based ligand (Scheme 1).…”

“…[22] The rigid naphthyridine core promotes ac lose interaction between two transition metals, and additional donor groups mayb ei ncorporated to enforce open binding sites for exploration of metal-metalc ooperativity in reactionc hemistry. [23][24][25] Moreover,n aphthyridine-based bimetallicc omplexes have been shown to catalyzearange of reactions. [26][27][28][29][30][31] However, these mostly symmetrical systems have so far been used to study homobimetallic complexes.…”

“…[32] This dinucleating ligand with distinct binding sites is based on an ovel unsymmetrical1 ,8-naphthyridine derivative, 2-(1,1di(pyridin-2-yl)ethyl)-7-((di-tert-butylphosphanyl)methyl)-1,8naphthyridine (dpepn). It features two moderately hard pyridine donors on one side, as in the symmetrical DPEN [23] and DPFN [24] environments, andasofter,e lectron-donatingd i-tertbutyl phosphine on the other.T he synthesis of this ligand was achievedi nt wo steps from 2-chloro-7-methyl-1,8-naphthyridine (Scheme 2). [34] First the substituted naphthyridine was added to lithiated 1,1-di-(2-pyridyl)ethane in THF at 0 8Ct o yield 2-ethyldipyridyl-7-methyl-1,8-naphthyridine.…”