The reactions of various thio- or oxothiomolybdates with the activated alkyne dicarbomethoxyacetylene, DMA, are described. The syntheses of the diamagnetic [Et4N]2[MoO(L)2] (I), anti-[Et4N]2[Mo2O2S2(L)2] (II), syn-[Ph4P]2[Mo2O2S2(L)2].2DMF (III), [Ph4P]2[Mo(L)3].DMF.C6H6 (IV), and [Ph4P]2[Mo2S2(L)4].2CH2Cl2 (V) complexes (L = 1,2-dicarbomethoxy-1,2-ethylenedithiolate, DMAD) are accomplished in reactions of DMA with (Et4N)2[MoO(S4)2], (Et4N)2[Mo2O2S9], (Ph4P)2-[Mo2OS7], (Ph4P)2[MoS(S4)2], and (Ph4P)2[Mo2S10/S12], respectively. It is proposed that these reactions proceed by electrophilic attack of DMA on either Mo = S or Mo-S2 with subsequent DMA insertion into these chromophores. The unstable vinyl sulfide or vinyl disulfide intermediates are converted to the final dithiolene products either thermally or by a sulfur-catalyzed pathway. The compounds I-V crystalize in the space groups P2(1)/c, P1BAR, P1BAR, C2/c, and P1BAR, respectively. The cell dimensions are a = 17.664 (4) angstrom, b = 9.979 (2) angstrom, c = 21.363 (4) angstrom, and beta = 100.5 (2)-degrees for I, a = 9.004 (2) angstrom, b = 8.975 (3) angstrom, c = 13.904 (2) angstrom, alpha = 90.53 (2)-degrees, beta = 102.04 (1)-degrees, and gamma = 112.11 (2)-degrees for II, a = 12.919 (4) angstrom, b = 14.863 (6) angstrom, c = 18.844 (6) angstrom, alpha = 95.86 (3)-degrees, beta = 102.61 (2)-degrees, and gamma = 93.74 (3)-degrees for III, a = 22.907 (14) angstrom, b = 14.619 (9) angstrom, c = 43.746 (21) angstrom, and beta = 95.34 (5)-degrees for IV, and a = 12.778 (2) angstrom, b = 13.616 (3) angstrom, c = 13.898 (3) angstrom, alpha = 105.62 (2)-degrees, beta = 98.80 (1)-degrees, and gamma = 110.10 (1) for V. The data for all structures were obtained on an automatic diffractometer employing Mo K-alpha radiation. Full-matrix refinement of 393 parameters on 2704 data for I, 217 parameters on 1774 data for II, 775 parameters on 6350 data for III, 389 parameters on 2637 data for IV, and 313 parameters on 2412 data for V gave final R(w) values of 0.050, 0.024, 0.044, 0.077, and 0.066, respectively. The structure of I shows the Mo(IV) coordinated by a terminal oxo ligand and two bidentate DMA ligands in the equatorial plane of the distorted square-pyramidal Mo(IV)(O)(S4) core unit (Mo = O = 1.686 (6) angstrom; Mo-S(eq) = 2.380 (4) angstrom). The structures of the anti- and syn-[Mo2O2(mu-2-S)2]2+ units in II and III have idealized C2h and C2-nu geometry, respectively. Each unit is coordinated by two DMAD bidentate ligands. The Mo(V)(O)(S4) subunits are distorted square pyramidal with a terminal oxo ligand and the DMAD and mu-2-S ligands occupying the equatorial planes. Adjacent pyramids share the bridging S ligands as common equatorial sites (for II, Mo-Mo = 2.904 (1) angstrom, Mo = O = 1.684 (2) angstrom, Mo-S(b) = 2.328 angstrom, Mo-S(L) = 2.419 angstrom, Mo-S(b)-Mo = 77.13 (1)-degrees, and S(b)-Mo-S(b) = 102.91 (1)-degrees; for III, Mo-Mo = 2.853 (1) angstrom, Mo = O = 1.675 (2) angstrom, Mo-S(b) = 2.331 (3) angstrom, Mo-S(L) = 2.425 (8) angstrom, Mo-S(b)-Mo = 75.5 (1)-degrees, and S(b)-Mo-S(b) = 100.9 (1)-degrees). The structure of IV shows the Mo(IV) coordinated by three bidentate DMAD ligands and contains the slightly distorted trigonal prismatic [Mo(IV)(S)6] core (Mo-S(L) = 2.393 angstrom). The structure of the centrosymmetric anion in V contains two edge-sharing distorted octahedral [Mo(V)(S)6] units that share the bridging S ligands. The Mo(V) in each of these subunits, in addition to the two bridging sulfides, is coordinated by two bidentate DMAD ligands (Mo-Mo = 2.938 angstrom, Mo-S(b) = 2.321 angstrom, Mo-S(L) = 2.383, 2.459 angstrom; Mo-S(b)-Mo = 78.6 (1)-degrees, S(b)-Mo-S(b) = 101.4 (1)-degrees). The different Mo-S(L) bonds in V are attributed to a significant trans effect of the bridging ligands. The spectroscopic and electrochemical properties of these complexes as well as a discussion of the reactivity characteristics of the various Mo-centered functional groups are discussed.
