Vier anionische Formen des Liganden Bis[N‐(2,6‐diisopropylphenyl)imino]acenaphthen (dpp‐bian) wurden durch Reduktion mit Natrium in Diethylether in präparativem Maßstab erhalten. Die Natriumsalze des Mono‐, Di‐, Tri‐ und Tetraanions (siehe Bild) wurden durch Einkristall‐Röntgenstrukturanalyse eindeutig charakterisiert.

The reduction of 1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene (2,6‐iPr2C6H3‐BIAN) with metallic magnesium or calcium in THF affords the monomeric complexes (2,6‐iPr2C6H3‐BIAN)Mg(THF)3 (1) and (2,6‐iPr2C6H3‐BIAN)Ca(THF)4·(THF)1/2 (2). The crystallisation of 1 and 2 from benzene causes the removal of one of the coordinated THF molecules, yielding (2,6‐iPr2C6H3‐BIAN)Mg(THF)2·(C6H6)1/2 (3a) and (2,6‐iPr2C6H3‐BIAN)Ca(THF)3 (4). Repeated recrystallisation of 1 from benzene gives (2,6‐iPr2C6H3‐BIAN)Mg(THF)2·(C6H6)2 (3b). Although the crystals of 3a and 3b differ in colour and in their crystallographic parameters, their molecular dimensions are very similar. Recrystallisation of 1 from pyridine produces (2,6‐iPr2C6H3‐BIAN)Mg(py)3·(py)2 (5). Complexes 1−5 have been characterised by elemental analysis, UV, IR and 1H NMR spectroscopy, as well as by single‐crystal X‐ray diffraction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

One ligand, four anions! Four anionic forms of a single ligand bis[N‐(2,6‐diisopropylphenyl)imino]acenaphthene (dpp‐bian) were isolated on a preparative scale for the first time and unambiguously characterized by single‐crystal X‐ray structure analysis. The ligand, dpp‐bian, may be easily reduced in diethyl ether by sodium metal to give the mono‐, di‐, tri‐, or tetranion (depicted).

Metal exchange reactions of the magnesium complexes (dpp-BIAN)Mg(THF) n , (dtb-BIAN)Mg(THF) n , and (bph-BIAN)Mg(THF) n with GeCl2(dioxane) afford the stable germylenes (dpp-BIAN)Ge (1), (dtb-BIAN)Ge(Et2O) (2), and (bph-BIAN)Ge (3), respectively (dpp-BIAN = 1,2-[(2,6-iPr2C6H3)N]2C12H6, dtb-BIAN = 1,2-[(2,5-tBu2C6H3)N]2C12H6, bph-BIAN = 1,2-[(2-PhC6H4)N]2C12H6). Compound 1 is also obtained from (dpp-BIAN)Na4 and GeCl4 in Et2O. The germylenes 1−3 were characterized by elemental analyses, 1H NMR, 13C NMR, and IR spectroscopy, and X-ray crystal structure analyses. In the monomeric molecules the two imino nitrogen atoms coordinate the germanium atom. The aryl(N) groups are arranged rather orthogonal to the acenaphthenediimine plane. Compound 3 shows an anti geometry with the ortho phenyl substituents of both N-phenyl rings positioned on opposite sides of the acenaphthenediimine plane. The bite angles N−Ge−N are 85.2° (1) and 85.0° (3), respectively. The Ge−N bond distances in 1−3 range from 1.878 to 1.915 Å.

The reactivity of digallane (dpp-Bian)Ga-Ga(dpp-Bian) (1), which consists of redox-active ligand 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-Bian), has been studied. The reaction of 1 with I2 proceeds via one-electron oxidation of each of two dpp-Bian ligands to a radical-anionic state and affords complex (dpp-Bian)IGa-GaI(dpp-Bian) (2). Dissolution of complex 2 in pyridine (Py) gives monomeric compound (dpp-Bian)GaI(Py) (3) as a result of a solvent-induced intramolecular electron transfer from the metal-metal bond to the dpp-Bian ligands. Treatment of compound 3 with B(C6F5)3 leads to removal of pyridine and restores compound 2. The reaction of compound 1 with 3,6-di-tert-butyl-ortho-benzoquinone (3,6-Q) proceeds with oxidation of all the redox-active centers in 1 (the Ga-Ga bond and two dpp-Bian dianions) and results in mononuclear catecholate (dpp-Bian)Ga(Cat) (4) (Cat = [3,6-Q](2-)). Treatment of 4 with AgBF4 gives a mixture of [(dpp-Bian)2Ag][BF4] (5) and (dpp-Bian)GaF(Cat) (6), which both consist of neutral dpp-Bian ligands. The reduction of benzylideneacetone (BA) with 1 generates the BA radical-anions, which dimerize, affording (dpp-Bian)Ga-(BA-BA)-Ga(dpp-Bian) (7). In this case the Ga-Ga bond remains unchanged. Within 10 min at 95 °C in solution compound 7 undergoes transformation to paramagnetic complex (dpp-Bian)Ga(BA-BA) (8) and metal-free compound C36H40N2 (9). The latter is a product of intramolecular addition of the C-H bond of one of the iPr groups to the C═N bond in dpp-Bian. Diamagnetic compounds 3, 5, 6, and 9 have been characterized by NMR spectroscopy, and paramagnetic complexes 2, 4, 7, and 8 by ESR spectroscopy. Molecular structures of 2-7 and 9 have been established by single-crystal X-ray analysis.