CROWN THIOETHER LIGANDS CONTAINING RIGID XYLYL UNITS - SYNTHESIS AND STRUCTURES OF 2,5,8-TRITHIA[9]-O-BENZENOPHANE (TTOB), 2,5,8-TRITHIA[9]-M-BENZENOPHANE (TTMB), AND FAC-MO(CO)3(TTOB).DMSO

The crown thioethers 2,5,8-trithia[9]-o-benzenophane (TTOB) and 2,5,8-trithia[9]-m-benzenophane (TTMB) were prepared by the reaction of the dipotassium salt of 3-thiapentane-1,5-dithioi with α,α′-dibromo-o-xylene and α,α′-dibromo-m-xylene, respectively. These compounds were characterized by 1H and 13C{1H} NMR, GCMS, and X-ray crystallography methods. The ortho isomer crystallized in the space group P21/n, with a = 8.840 (2) Å, b = 15.866 (5) Å, c = 10.600 (2) Å., β = 119.34 (6)°, V = 1295.9 (6) Å3, and Z = 4. The structure was refined to R = 4.80% and Rw= 5.51% for 1034 reflections with F02> 3σ(F02). The meta isomer crystallized in the space group P2l2l2i, with a = 9.107 (5) Å, b = 8.851 (7) Å, c = 31.90 (2) Å, V= 2571 (1) Å3, and Z = 8. The structure refined to R = 6.59% and /Rw= 7.04% for 1384 reflections with F02> 3σ(F2). In both structures, the S atoms are exodentate to the ring with a-SCH2CH2SCH2CH2S-“bracket” bridging the xylyl group and the plane of the aromatic ring approximately perpendicular to the mean plane of the S atoms. Molecular mechanics calculations (MMX) indicated the possibility of a conformation for TTOB, with all S atoms endodentate, which would be ideal for facial coordination to a metal center. The reaction of TTOB with fac-Mo(CH3CN)3(CO)3gave the complex/ac-Mo(CO)3(TTOB), showing that the predicted facial coordination mode is possible in octahedral geometry. The complex fac-Mo(CO)3(TTOB)-DMSO crystallized in the space group P21/c, with a = 7.732 (4) Å, b= 18.69 (2) A, c = 15.00 (1) Å, β = 104.05 (6)°, V= 2103 (1) Å3, and Z = 4. The structure was refined to R = 4.52% and Rw= 5.44% for 2174 reflections with F02> 3σ(F02). The analogous coordination mode for TTMB was neither indicated by molecular mechanics calculations nor observed in similar complexation studies. © 1990, American Chemical Society. All rights reserved.