Structures of nickel-, copper-, and zinc-salophen derivatives.

Salen-type tetradentate Schiff base ligands are ubiquitous in coordination chemistry because of their straightforward synthesis, derivatization, and versatility as ligands for metals across the periodic table. The present work was motivated by our interest in expanding the library of bifunctional salophen systems, where basic sites are incorporated in the secondary coordination sphere of salophen-ligated metals. Here, we report and describe seven previously unreported structures of nickel-, copper-, and zinc-salophen derivatives, including two complexes that integrate amine bases in the ligand periphery. These are {4,4'-di-tert-butyl-2,2'-[1,2-phenylenebis(nitrilomethylidyne)]diphenolato}nickel(II) toluene 1.33-solvate, [Ni(C28H30N2O2)]·1.33C7H8 or (tBu-salophen)Ni·1.33C7H8, {4,4'-di-tert-butyl-2,2'-[1,2-phenylenebis(nitrilomethylidyne)]diphenolato}copper(II), [Cu(C28H30N2O2)] or (tBu-salophen)Cu, aqua{4,4'-di-tert-butyl-2,2'-[1,2-phenylenebis(nitrilomethylidyne)]diphenolato}zinc(II) tetrahydrofuran monosolvate, [Zn(C28H30N2O2)(H2O)]·C4H8O or (tBu-salophen)Zn(OH2)·THF, {4,4'-bis(trifluoromethyl)-2,2'-[1,2-phenylenebis(nitrilomethylidyne)]diphenolato}nickel(II), [Ni(C22H12F6N2O2)] or (CF3-salophen)Ni, {4,4'-bis(trifluoromethyl)-2,2'-[1,2-phenylenebis(nitrilomethylidyne)]diphenolato}(pyridine)zinc(II), [Zn(C22H12F6N2O2)(C5H5N)] or (CF3-salophen)Zn(py), {4,4'-di-tert-butyl-6,6'-bis[(diisopropylamino)methyl]-2,2'-[1,2-phenylenebis(nitrilomethylidyne)]diphenolato}nickel(II), [Ni(C42H60N4O2)] or (tBu-salophen-NiPr2)Ni, and {4,4'-di-tert-butyl-6,6'-bis[(diphenylamino)methyl]-2,2'-[(pyridine-3,4-diyl)bis(nitrilomethylidyne)]diphenolato}(pyridine)zinc(II) pyridine monosolvate, [Zn(C53H51NO2)(C5H5N)]·C5H5N or (tBu-salpyr-NPh2)Zn(py)·py. The metal centers in these compounds adopt structures consistent with what has been observed for other salen-type ligands described in the literature, with near ideal square-planar structures around nickel or copper, and a distorted square-pyramidal structure for the zinc complexes. The primary coordination sphere around these metals expands slightly across the row, as anticipated based on the increase in d-electron count from nickel to zinc. The solid-state packing of these compounds is also discussed, including the tendency for their flat extended π-systems to pack parallel to one another. Differences in packing are observed as functional groups at the ligand periphery are varied or where the compounds cocrystallize with solvent molecules.