Synthesis of an expanded pincer ligand and its bimetallic coinage metal complexes

Abstract

An expanded pincer ligand tBu-PONNOP (2,7-bis(di-tert-butylphosphinito)-1,8-naphthyridine) has been synthesised and its coordination to coinage metals has been studied. Bimetallic complexes were produced with metal halide salts of the type [M2X2(tBu-PONNOP)]...

Quantification of the Steric Properties of 1,8-Naphthyridine-Based Ligands in Dinuclear Complexes

“…With the established methods for quantifying the sterics of 1,8-naphthyridine complexes in hand, we sought to explore the influence of different ligand modifications on the steric properties of expanded pincer complexes. In this, we focused on PNNP type ligands of which several have been reported. ,,, These insights could help in selecting rational ligand modifications to alter the steric properties in the corresponding complexes.…”

“…The backbone of PNNP-expanded pincer complexes can be modified by adjusting the methylene linkers. They can, for example, be changed into heteroatoms such as oxygen to form PONNOP complexes. , For mononuclear complexes, the influence of such heteroatoms has been described before . Alternatively, the methylene linkers in the PNNP ligand can be deprotonated, which affects the rigidity of the ligand and the geometry in related complexes. , In addition to synthesizing complexes with such a deprotonated backbone, deprotonation can also occur during a reaction step in a catalytic cycle.…”

Quantification of the Steric Properties of 1,8-Naphthyridine Based Ligands in Dinuclear Complexes

“…In this, we focused on PNNP type ligands of which several have been reported. [31,32,40,41] These insights could help in selecting rational ligand modifications to alter the steric properties in the corresponding complexes.…”

“…They can for example be changed into heteroatoms such as oxygen to form PONNOP complexes. [31,41] For mononuclear complexes, the influence of such heteroatoms has been described before. [19] Alternatively, the methylene linkers in the PNNP ligand can be deprotonated, which affects the rigidity of the ligand and the geometry in related complexes.…”

Copper and Zinc Complexes of 2,7-Bis(6-methyl-2-pyridyl)-1,8-naphthyridine─A Redox-Active, Dinucleating Bis(bipyridine) Ligand

“…Bimetallic transition-metal complexes are attracting significant attention due to their prevalence in enzymatic catalysis as well as their synthetic potential. − As such, efforts to develop synthetic bimetallic systems have spurred much work in ligand design. , One candidate that has proven particularly promising as a ligand core is 1,8-naphthyridine, which is geometrically disposed to bind two metal centers in close proximity. The diversity with which donor arms at the 2,7-positions can be functionalized is reminiscent of conventional mononucleating pincer ligands, offering steric and electronic tuning as well as chelation stabilization, − and has earned these ligands the term expanded pincer ligands . We have become interested in 2,7-bis­(pyridyl)-1,8-naphthyridine systems (Figure a), which can instead be likened to dinucleating versions of ubiquitous bipyridine (bpy) ligands, that is, “bis­(bpy)” ligands.…”