Synthesis and Characterization of Aluminum- and Gallium-Bridged [1.1]Chromarenophanes and [1.1]Molybdarenophanes

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• 作者：Clinton L. Lund ; Jö ; rg A. Schachner ; Ian J. Burgess ; J. Wilson Quail ; Gabriele Schatte ; Jens Mü ; ller
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：July 7, 2008
• 年：2008
• 卷：47
• 期：13
• 页码：5992 - 6000
• 全文大小：496K
• 年卷期：v.47,no.13(July 7, 2008)
• ISSN：1520-510X

文摘

The synthesis and structural characterization of the first [1.1]chromarenophanes and the first [1.1]molybdarenophanes are described. A salt-metathesis reaction of [2-(Me₂NCH₂)C₆H₄]AlCl₂ with freshly prepared [Cr(LiC₆H₅)₂]·TMEDA (TMEDA = N,N,N′,N′-tetramethylethylenediamine) resulted in the dialumina[1.1]chromarenophane [{2-(Me₂NCH₂)C₆H₄}Al(η⁶-C₆H₅)₂Cr]₂ (2a). The poor solubility of 2a in organic solvents prompted us to synthesize the new intramolecularly coordinated aluminum- and gallium dichlorides [5-tBu-2-(Me₂NCH₂)C₆H₃]ECl₂ [E = Al (3a), Ga (3b)] in which the phenyl group was equipped with a tert-butyl group. Salt-metathesis reactions of 3a and 3b, respectively, with freshly prepared [M(LiC₆H₅)₂]·TMEDA (M = Cr, Mo) resulted in four new [1.1]metallarenophanes of the general type [{5-tBu-2-(Me₂NCH₂)C₆H₃}E(η⁶-C₆H₅)₂M]₂ [E = Al, M = Cr (4a); E = Ga, M = Cr (4b); E = Al, M = Mo (5a); E = Ga, M = Mo (5b)]. 2a, 4a,b, and 5a,b have been structurally characterized by single-crystal analysis [2a·1/2C₆H₁₂: C₄₈H₅₆Al₂Cr₂N₂, monoclinic, P2₁/c, a = 9.9117(9) Å, b = 19.9361(16) Å, c = 10.638(2) Å, α = 90°, β = 112.322(5)°, γ = 90°, Z = 2; 4a·2C₆H₆: C₆₂H₇₂Al₂Cr₂N₂, monoclinic, P2₁/c, a = 10.9626(9) Å, b = 19.3350(18) Å, c = 12.4626(9) Å, α = 90°, β = 100.756(5)°, γ = 90°, Z = 2; 4b·2C₆H₆: C₆₂H₇₂Cr₂Ga₂N₂, monoclinic, P2₁/c, a = 10.8428(2) Å, b = 19.4844(4) Å, c = 12.4958(2) Å, α = 90°, β = 100.6187°, γ = 90°, Z = 2; 5a·2C₆H₆: C₆₂H₇₂Al₂Mo₂N₂, triclinic, P1t face="Arial Unicode MS,Lucida Sans Unicode,Code2000,GNU Unifont">̅t>, a = 10.4377(4) Å, b = 11.6510(4) Å, c = 11.6514(4) Å, α = 73.545(3)°, β = 89.318(2)°, γ = 76.120(2)°, Z = 1; 5b·2C₆H₆: C₆₂H₇₂Ga₂Mo₂N₂, triclinic, P1t face="Arial Unicode MS,Lucida Sans Unicode,Code2000,GNU Unifont">̅t>, a = 10.3451(5) Å, b = 11.6752(6) Å, c = 11.6900(5) Å, α = 73.917(3)°, β = 89.550(3)°, γ = 76.774(2)°, Z = 1]. All five [1.1]metallarenophanes 2a, 4a,b, and 5a,b crystallize as anti isomers with both Me₂N donor groups in exo positions (C_i point group symmetry). The new [1.1]metallarenophanes show NMR spectra that can be interpreted as being caused by time-averaged C_2h symmetrical species, which is consistent with the findings of their molecular structures in the solid state. Variable-temperature ¹H NMR measurements for 4a,b and 5a,b (500 MHz; −90 to 90 °C) revealed only peak broadening in the lower temperature range of −70 to −90 °C. ¹H NMR saturation transfer difference experiments did not show an expected anti-to-anti isomerization, rendering the new [1.1]metallacyclophanes rigid on the NMR time scale. Electrochemical measurements were performed for 4a,b and 5a,b. However, reproducible cyclic voltammograms could only be obtained for the two gallium species 4b and 5b, revealing the expected weak communication between the two transition-metal atoms in both compounds (class II).