Preparation and Crystal and Molecular Structure of a Tris(thiobenzoyldiazene)molybdenum Complex: An Example of Distorted Trigonal-Prismatic Coordination

Molybdenum dioxobis(acetylacetonate), [Mo02(acac)2], or sodium molybdate reacts with the thioaroylhydrazines RNHNHCSR' (R = H, R' = C6H5, p-MeC6H4, p-MeOC6H4; R = Ph, R' = PhCH2, 1-C10H7, p-MeC6H4, p-MeOC6H4) to give the dark green or black complexes [Mo(RN2CSR')3]. The structure of tris(thiobenzoyldiazene)molybdenum-(Vl)-dimethylformamide, [Mo(C6H5CSN2H)3KCH3)2NCHO, has been determined in a single-crystal X-ray diffraction study. The coordination geometry of the molybdenum is a distorted trigonal prism of sulfur and nitrogen donor atoms contributed by three chelating diazene ligands disposed in a facial configuration. The distortion may be expressed in terms of an average twist angle of 7°, compared to the value of a - 0° for a regular trigonal prism. The average molybdenum-sulfur bond distance is 2.400 (5) A and the average molybdenum-nitrogen bond distance is 2.03 (1) A. The bond lengths in the chelate ring systems Mo-N-N-C-S- are intermediate between single- and double-bond distances, suggesting considerable derealization of charge: N-N(av) = 1.32 (2), N-C(av) = 1.35 (2) A, C-S(av) = 1.69 (2) A. The complex crystallizes in the orthorhombic system, space group Pbca, with a = 17.458 (8) A, b = 17.541 (9) A, and c = 17.896 (9) A. The measured density of 1.51 ± 0.03 g/cm3 requires eight molecules per unit cell (pcaic(1 = 1.50 g/cm3). The structure was solved by conventional Patterson and Fourier synthesis methods from 1456 independent reflections with I > 2.58<r(/). Full-matrix least-squares refinement of all atoms, excluding hydrogens, converged at values for Rt = 0.071 and R2 = 0.077.