Dimeres 1,4‐Dichlor‐2,3,5,6‐tetramethyl‐1,4‐dialumina‐2,5‐cyclohexadien, eine Verbindung mit Aluminium‐Olefin‐π‐Bindungen

Abstract

Da das Reagens 2 gegen Monoketone praktisch inaktiv ist (Tabelle 1, Nr. 10 und 1 I), fuhren wir die uberraschend gute Olefinierung von Dicarbonylverbindungen nach Schema 4 darauf zuriick, da13 die zweite Carbonylgruppe als aktivierende Base wirkt. 5 3 9% 2 6% 6 52% Schema 4. Lt)sungsmittel: THF. Molverhaltnisse: 5 : 2 = 1 : I ; 6 : 2 -1 : I Tabelle I. Beispiele fur Carbonylolefinierungen [a]. Nr. Rea-Substrat Rea-Olefin-Rllckger 1 2 8 Kation 3, m = n = 3 Dikation 4, 1 = m = n = 3[*] Prof.

Two Isomers with an Al4C8 Framework

“…Der Röntgenstruktur-analyse zufolge liegen in den Kristallen dieser Verbindung zwei Isomere vor, die als 1,4-Dialumina-2,5-cyclohexadien bzw. als 1,4,7,5,8, bonds (232.6 ± 242.0 pm in 2 b and 236.0 ± 240.9 pm in 2 a/2 c) do not differ very much. This observation seems plausible, since in the crystallisation of 2 the two isomers are formed in a ratio of 2:1 (2 a/2 c:2 b), and their energy should therefore be very similar.…”

“…The NMR data of 5 were taken from spectra of a mixture of the two compounds. 1 8, 26.4, 16.6, 14.1; 27 Al NMR (C 6 D 6 , 25 8C): 119 (w 1/2 % 4000 Hz). This broad resonance signal is presumably due to the presence of both 2 and 5.…”

“…The resulting solution was warmed slowly up to room temperature, the solvent partially removed in vacuo, and the solution held at 4 8C, yielding colourless crystals. 1 [12e] 463. 9 (77;1 ),448.9 (11;1 À Me),409.9 (6),402.0 (7),367.0 (38),347.9 (35),293.9 (36),232.0 (57;4 À 2Et 2 O),197.0 (36),170 (40), 74 (54; Et 2 O ).…”

“…1 [12e] 463. 9 (77;1 ),448.9 (11;1 À Me),409.9 (6),402.0 (7),367.0 (38),347.9 (35),293.9 (36),232.0 (57;4 À 2Et 2 O),197.0 (36),170 (40), 74 (54; Et 2 O ).…”

“…Some years ago we reported the preparation and structure of the dimeric 1,3,5, 4 (1), formed from the high-temperature molecule AlCl and 2-butyne ( Figure 1). …”