Electron Release and Proton Acceptance Reactions of (dpp-BIAN)Mg(THF)3

(dpp-BIAN)Mg(THF)3 (1) (dpp-BIAN = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) and (PhCOO)2 react with splitting of the peroxide bridge and formation of the dimeric magnesium benzoate [(dpp-BIAN)MgOCOPh(THF)]2 (2). The reaction of 1 with PhCOOH yields the dimeric magnesium benzoate [(dpp-BIAN)(H)MgOCOPh(THF)]2 (3), whereas 1 and furanyl-2-carboxylic acid react with liberation of hydrogen and formation of (dpp-BIAN)Mg[OCO(2-C4H3O)]2 Mg(dpp-BIAN)(THF) (4). Compounds 2, 3, and 4 have been characterized by elemental analysis, IR spectroscopy, and X-ray structure analysis, compound 3 also by 1H NMR spectroscopy. The eightmembered metallacycles of the centrosymmetric dimers 2 and 3 are almost completely planar. The two magnesium atoms in 4 show different coordination spheres; one is surrounded by its ligands in a trigonal bipyramidal manner, the other one in a tetrahedral fashion. The Mg···Mg separations in 2, 3 and 4 are 4.236, 4.296, and 4.030 Å, respectively

Organometallic Compounds of the Lanthanides 182 [1]. Calcium and Neodymium Complexes Containing the dpp-BIAN Ligand System: Synthesis and Molecular Structure of [(dpp-BIAN)CaI(THF)2]2 and [(dpp-BIAN)NdCl(THF)2]2

Oxydation of (dpp-BIAN)Ca(THF)4 with 0.5 equiv. of I2 in THF yields [(dpp-BIAN)CaI(THF)2]2 (1). A corresponding neodymium compound [(dpp-BIAN)NdCl(THF)2]2 (2) has been obtained by reaction of (dpp-BIAN)Na2 with NdCl3 in THF. The X-ray single crystal structure analyses show 1 and 2 to be isostructural dimers containing octahedrally coordinated metal atoms bridged by the respective halides. The chelating dpp-BIAN ligand acts as a radical anion in the Ca2+ complex 1 and as a dianion in the Nd3+ complex 2, respectively.DFG, SPP 1166, Lanthanoidspezifische Funktionalitäten in Molekül und Materia

Lanthanum Complexes with a Diimine Ligand in Three Different Redox States

The reduction of 1,2-bis­[(2,6-diisopropylphenyl)­imino]­acenaphthene (dpp-Bian) with an excess of La metal in the presence of iodine (dpp-Bian/I₂ = 2/1) in tetrahydrofuran (thf) or dimethoxyethane (dme) affords lanthanum­(III) complexes of dpp-Bian dianion: deep blue [(dpp-Bian)^2–­LaI­(thf)₂]₂ (<b>1</b>, 84%) was isolated by crystallization of the product from hexane, while deep green [(dpp-Bian)­LaI­(dme)₂] (<b>2</b>, 93%) precipitated from the reaction mixture in the course of its synthesis. A treatment of complex <b>1</b> with 0.5 equiv of I₂ in thf leads to the oxidation of the dpp-Bian dianion to the radical anion and results in the complex [(dpp-Bian)^1–­LaI₂(thf)₃] (<b>3</b>). Addition of 18-crown-6 to the mixture of <b>1</b> and NaCp* (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) in thf affords ionic complex [(dpp-Bian)^2–­La­(Cp*)­I]­[Na­(18-crown-6)­(thf)₂] (<b>4</b>, 71%). In the absence of crown ether the alkali metal salt-free complex [(dpp-Bian)^2–­LaCp*­(thf)] (<b>5</b>, 67%) was isolated from toluene. Reduction of complex <b>1</b> with an excess of potassium produces lanthanum–potassium salt of the dpp-Bian tetra-anion {[(dpp-Bian)^4–­La­(thf)]­[K­(thf)₃]}₂ (<b>6</b>, 68%). Diamagnetic compounds <b>1</b>, <b>2</b>, <b>4</b>, <b>5</b>, and <b>6</b> were characterized by NMR spectroscopy, while paramagnetic complex <b>3</b> was characterized by the electron spin resonance spectroscopy. Molecular structures of <b>2</b>–<b>6</b> were established by single-crystal X-ray analysis

Main-group metal complexes of α-diimine ligands: structure, bonding and reactivity

α-Diimine ligands, in particular 1,4-diazabutadiene (dad) and bis(iminoacenaphthene) (bian) derivatives, have been widely used for coordination with various metals, including main-group, transition, and lanthanide and actinide metals. In addition to their tunable steric and electronic properties, the dad and bian ligands are redox-active and can readily accept one or two electrons, converting into the radical-anionic (L˙−) or dianionic (enediamido, L2−) form, respectively. This non-innocence brings about rich electronic structures and properties of the ligands and complexes thereof. For example, the dad ligands in their three redox levels can effectively stabilize a series of metal centers in different oxidation states, including low-valent metals. Moreover, these ligands can serve as electron reservoirs and can participate in reactions toward other molecules with or without metals. Therefore, such ligands are extremely useful in the areas of low-valent complexes and small molecule activation. Herein, we will discuss the use of dad (and bian) ligands in the stabilization of metal–metal-bonded compounds, in particular those of main-group metals, as well as small molecule activation by these (low-valent) metal coordination species where the non-innocence of the ligands plays a key role