Dedicated to Professor Gernot Boche on the occasion of his 65th birthdaySekiguchi et al. recently described the planar dianion 1, a sixelectron aromatic four-membered ring (Scheme 1).[1a] Upon two-electron oxidation, 1 is transformed into the antiaromatic compound 2, [1b] and double protonation, which requires four electrons for bonding the two protons, produces the nonaromatic compound 3.[1a] Thus, both reactions proceed with loss of aromaticity. Here we present the puckered dianions 4 a and 4 b (Scheme 2), aromatic two-electron four-membered rings of type 4, the corresponding reactions of which result in compounds of types 5 and 6, conserving the aromaticity.Dianion 4 a is obtained by treating 5 a [2,3] with lithium in DME at 25 8C. Treatment with hexachloroethane quantitatively reoxidizes 4 a to 5 a, whereas the reaction of 4 a with Et 2 NBCl 2 results in the formation of amino(triboryl)tetraborane(4) 5 c. Compound 4 b, which is obtained by the reaction of 5 b [4] with lithium in THF at À78 8C, is stable in solution below À30 8C; at higher temperatures a recently described [5] double aromatic B 3 ring is formed by migration of a trimethylsilyl

1.4-Diiodotetrafluorobenzene, Donor-Acceptor Complexes, Crystal Structure (Ph4P)X as well as (Me4N)X (X = Cl, Br, I) react with 1,4-diiodotetrafluorobenzene in CH 2C12 and CH 3CN solutions, respectively, to give the donor- (6 ) and (Me4N)2[(C6F4I2)3I2] (7). All complexes have been characterized by single X-ray crystallographic structure determinations. pm. In all complexes the acceptor molecule C6F4I2 coordinates with the halide donor ions in linear arrangements C-I-• X" . In 1 and 2 the halide ions act as terminal donors to form the dianionic species [X-• I-C6F4-I-• X]2-(X = Cl, Br). Complexes 3 and 4 form polymeric anionic zigzag chains with ju-X~ bridges and bond angles I-• -Cl-• I of 77.2° and I-• -Br-• I of 74.3°. Complexes 5 -7 are characterized by three-dimensional anionic networks via /x3-X_ bridging halide ions and //-bridging 1,4-diiodotetrafluorobenzene molecules.

Professor Joachim Strähle zum 65. Geburtstag gewidmetInhaltsübersicht. Die einfache Synthese von Dialkylgalliumhydriden (R ϭ Me, Et, iPr, iBu, Neopentyl) gelingt nach zwei unterschiedlichen Methoden. Dimethyl-und Diethylderivate bilden sich bei der Umsetzung von LiH mit den entsprechenden Dialkylgalliumchloriden über bisher nicht in reiner Form isolierte Lithiumdialkyldihydridogallat-Intermediate. Die übrigen Verbindungen wurden durch Substituentenaustausch bei der Umsetzung von Abstract. Dialkylgallium hydrides (R ϭ Me, Et, iPr, iBu, neopentyl) were obtained on two different synthetic routes. The dimethyl and diethyl compounds were formed by the reaction of LiH with the corresponding dialkylgallium chlorides via lithium dialkyldihydridogallate intermediates, which so far have not been isolated in a pure form. On the second route, trialkylgallium compounds were treated with [GaH 3 ·NMe 2 Et] to yield the dialkylgallium hydrides Einleitung

One extremely short and two relatively long BB bonds are found for the B3 ring of compounds 1 and 2. This characteristic of three‐membered, two‐electron double aromatic compounds was predicted as early as 1994 and has now been experimentally realized for the first time. A=SiMe3.

LiNPPh3 reagiert mit den Cyclooctatetraenid‐Komplexen [Ln(C8H8)Cl(THF)2]2 von Cer und Samarium in THF‐Lösung unter Bildung der Phosphaniminato‐Komplexe [Ln(C8H8)Li3Cl2(NPPh3)2(THF)3], in denen nach Kristallstrukturanalysen Heterocuban‐Strukturen unter Beteiligung des Lanthanoid‐Metallatoms, der drei Li‐Atome sowie der beiden Cl‐ und der beiden N‐Atome der NPPh3–‐Gruppen vorliegen. Die Kristallstruktur von LiNPPh3 zeigt hexamere Moleküle mit einem Li6N6‐Polyeder, das peripher durch die Phenylgruppen abgeschirmt ist. Die Struktur des als Nebenprodukt isolierten [Li(THF)4][Sm(C8H8)2] enthält das Samarium‐Atom in sandwichartiger Koordination durch die beiden η8‐C8H82–‐Ringe, wie es auch von den entsprechenden Anionen mit Cer und Neodym bekannt ist.