1035458-31-1Relevant articles and documents
Synthesis and characterization of aluminum- and gallium-bridged [1.1]chromarenophanes and [1.1]molybdarenophanes
Lund, Clinton L.,Schachner, Joerg A.,Burgess, Ian J.,Quail, J. Wilson,Schatte, Gabriele,Mueller, Jens
, p. 5992 - 6000 (2008)
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)C 6H4]AlCl2 with freshly prepared [Cr(LiC 6H5)2]·TMEDA (TMEDA = N,N,N′,N′-tetramethylethylenediamine) resulted in the dialumina[1.1]chromarenophane [{2-(Me2NCH2)-C 6H4}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)C6H 3]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-(Me2NCH 2)C6H3}E(η6-C6H 5)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·1/2C 6H12: C48H56Al2Cr 2N2, monoclinic, P21/c, a = 9.9117(9) A, b = 19.9361(16) A, c = 10.638(2) A, α = 90°, β = 112.322(5)°, γ = 90°, Z = 2; 4a·2C6H 6: C62H72Al2Cr2N 2, monoclinic, P21/c, a = 10.9626(9) A, b = 19.3350(18) A, c = 12.4626(9) A, α = 90°, β = 100.756(5)°, γ = 90°, Z = 2; 4b·2C6H 6: C62H72Cr2Ga2N 2, monoclinic, P21/c, a = 10.8428(2) A, b = 19.4844(4) A, c = 12.4958(2) A, α = 90°, β = 100.6187°, γ = 90°, Z = 2; 5a·2C6H6: C62H72Al2Mo2N2, triclinic, P1, a = 10.4377(4) A, b = 11.6510(4) A, c = 11.6514(4) A, α = 73.545(3)°, β = 89.318(2)°, γ = 76.120(2)°, Z = 1; 5b·2C6H6: C 62H72Ga2Mo2N2, triclinic, P1, a = 10.3451(5) A, b = 11.6752(6) A, c = 11.6900(5) A, 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 (Ci point group symmetry). The new [1.1]metallarenophanes show NMR spectra that can be interpreted as being caused by time-averaged C2h 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).
