SYNTHESIS, X-RAY STRUCTURES, AND SPECTROSCOPIC AND MAGNETIC-PROPERTIES OF A SERIES OF ISOMERIC BINUCLEAR MOLYBDENUM(III) COMPLEXES OF GENERAL FORMULA MO2CL6L3 (L = THIOETHER) - LARGE STRUCTURAL INFLUENCE OF BRIDGING LIGANDS IN CONFACIAL BIOCTAHEDRAL COMPLEXES

The syntheses, spectroscopic characterization, and X-ray crystal structures of two isomeric forms of Mo2Cl6(THT)3(THT = C4H8S, tetrahydrothiophene) are reported and compared with those of (Me2S)CI2Mo(?-Me2S)(?-Cl)2MoCl2(Me2S) and the anion [(Me2S)Cl2Mo(?-CI)3MoCl2(Me2S)]-. The most notable feature of these structures, which have a confacial bioctahedral framework, is that those which have the core structure Mo(?-Cl)3Mo have relatively long Mo-Mo bond lengths and display antiferromagnetic behavior, while those with one ?-Cl replaced by a ?-thioether have much shorter Mo-Mo bonds, in the range expected for Mo?Mo bonding, and are diamagnetic. By following the interconversion of two isomers of Mo2Cl6(Me2S)3in C2D2Cl4solution at 70 ° by 1HNMR spectroscopy, it was inferred that the process is intramolecular, likely involving ligand exchange between terminal and bridging sites. The complex (THT)Cl2Mo(?-THT)(?-Cl)2MoCl2(THT) (4) crystallizes with 1 mol of CH2Cl2in the triclinic space group P1 with Z = 2 in a cell of dimensions a = 8.595 (1) Å, b = 11.165 (4) Å, c = 15.143 (3) Å, a = 70.60 (2)°, ? = 73.94 (1)°, and ? = 77.33 (2)°. The least-squares refinement, with anisotropic thermal parameters for all non-hydrogen atoms, converged at R = 0.071 and Rw= 0.050 for 5583 unique observed reflections. The complex meso-(THT)Cl2Mo(?-Cl)3MoCl(THT)3(5a) crystallized in the monoclinic space group P21/n with Z = 4 in a cell of dimensions a = 10.522 (2) Å, b = 12.124 (2) Å, c = 18.262 (3) Å, and ? = 98.91 (1)°. The least-squares refinement, with anisotropic thermal parameters for all non-hydrogen atoms, converged at R = 0.083 and Rw= 0.043 for 7938 unique observed reflections. © 1990, American Chemical Society. All rights reserved.