Synthesis, Structure, and Dynamic Properties of W(S)(PhC₂Ph)(S₂CNEt₂)₂, a Sulfidotungsten(IV) Alkyne Complex

Synthesis of W(S)(PhC₂Ph)(S₂CNEt₂)2 (1) has been accomplished by oxidation of W(CO)-(PhC₂Ph)(S₂CNEt₂)2 with cyclohexene sulfide. The molecular structure of 1 has been determined by a single-crystal X-ray diffraction study. The crystals were found to be monoclinic of space group P2₁/n with a = 10.175 (7) Å, b = 14.165 (6) Å, c = 19.279 (39) Å, and β = 94.97 (2)°. The unit cell contains one independent molecule per asymmetric unit; the structure was refined to R = 0.064 and R_w = 0.079 with the use of 3623 reflections with I > 3σ(I). The molecular geometry can be described as a distorted octahedron. The alkyne ligand is cis to the terminal sulfide with the C₂ unit nearly perpendicular to the W=S moiety. A rearrangement of the chelating ligands, perhaps via dissociation of the dithiocarbamate sulfur trans to the terminal sulfide to form a fluxional five-coordinate intermediate, is compatible with dynamic NMR data obtained for 1. A related minor product, W(S)(PhC₂Ph)(S₂CNEt₂)(SCNEt₂), is believed to result from internal oxidative addition of one of the dithiocarbamate C-S bonds to the W(II) center of the W(CO) (PhC₂Ph) (S₂CNEt₂)₂ reagent.