Crystal and molecular structures of novel (arene)chromium tricarbonyl complexes (Aminobenzenes ; 18)

Abstract

Several new (1,3,5-tris(dialkylamino)benzene)chromium tricarbonyl (chromium tricarbonyl = TCC) complexes (2) were prepared and crystal structures for two of them, 2a ((1,3,5-tripyrrolidinobenzene)TCC) and 2b ((1,3,5-tripyrrolidino-2-methylbenzene)TCC), were determined to high precision with X-ray data collected from cooled crystals (T ≈ 120 K). Complex 2a crystallizes in space group symmetry P1 with a = 8.7670 (5) A, b = 10.6023 (8) A, c = 11.6337 (8) A, α = 66.724 (6)°, β = 72.560 (6)°, γ = 79.651 (7)°, and Z = 2. For 2b the space group is P2 l/c with a = 12.323 (1) A, b = 8.2651 (8) A, c = 23.902 (2) A, β = 123.114 (7)°, and Z = 4. The model for 2a was refined with 13 110 contributing reflections to give Rw = 0.053; for 2b refinement with 9154 reflections gave Rw = 0.058. A crystal structure was also determined for the [(phenyl(trimethylsiloxy)methyl)benzene]TCC complex (3) for which the space groups is P2 1/c with a = 6.282 (1) A, b = 11.319 (4) A, c = 26.962 (12) A, β = 93.82 (2)°, and Z = 4 (room temperature). All three complexes display a close approximation to the syn-e conformation for the (arene)TCC moiety. The rotational barriers for compounds 2 could not be established because of their low solubility. The application of conclusions from crystal structures to reaction behavior in solution was proved in the case of the [(phenyl)trimethylsiloxy)methyl)benzene]TCC complex (3). The experimental results are in agreement with the reactivity pattern calculated for the crystal structure determined for 3.