Preparation and Characterization of Di-μ-sulfido Binuclear Compounds of W(IV) and W(V). Unambiguous Examples of Formal Single and Double Bonds between Tungsten Atoms

The preparation and structural characterization of two compounds containing tungsten-tungsten bonds of orders 1 and 2 in very similar environments are reported. In 1, W2(μ-S)2(Et2NCS2)2(μ-Et2NCS2), the W-W distance, 2.530 (2) Å, corresponds to a double bond, while in 2, W2(Å-S2)(Et2NCS2)2(CH3O)4, the W-W distance of 2.791 (1) Å is consistent with a single bond. While the assignment of M-M bond order in any one molecule with bridging ligands is frequently ambiguous, the totality of the data for this pair of structurally analogous molecules makes these two bond order assignments very secure. Both compounds are easy to prepare and can be handled in the air. Crystallographic data are as follows. 1: space group C2/c, a = 21.37 (2) Å, b = 9.211 (5) Å, c = 18.367 (8) Å, β = 108.31 (4)°, Z = 4. The structure was refined to final residuals of R1, = 0.047 and R2 = 0.057. For 2: space group P2/c, a = 9.028 (4) Å, b = 12.776 (8) Å, c = 12.126 (4) Å, β = 112.29 (3)°, Z = 2; final residuals were 0.041 and 0.053.