The reaction of Mo-2(SCH2CH2S)(2)Cp-2 (1; Cp = eta-C5H5) with an excess of an alkyne in refluxing dichloromethane affords the bis(dithiolene) complexes Mo-2(mu-SCR1 =(CRS)-S-2)(2)Cp-2 (2a, R-1 = R-2 = CO2Me; 2b, R-1 = R-2 = Ph; 2c, R-1 = H, R-2 = CO2Me) whereas with 1 equiv of alkyne at room temperature the mixed dithiolene-dithiolate species Mo-2(mu-SCR1 =(CRS)-S-2)(mu-SCH2CH2S)Cp-2 (3a, R-1 = R-2 = CO2Me; 3b, R-1 = R-2 = Ph) are formed. The remaining dithiolate ligand in 3 can then be converted into a different dithiolene by reaction with a second alkyne. Applying this methodology, we have used bis(diphenylphosphino)acetylene to prepare the first examples of complexes containing phosphine-substituted dithiolene ligands: Mo-2{mu-SC(CO2Me)= C(CO2Me)S}{mu-SC(PPh2)= C(PPh2)S}Cp-2 (2g) and Mo-2{mu-SC(PPh2)= C(PPh2)S}(2)Cp-2 (2h). Tri- and tetrametallic complexes can then be assembled by coordination of these diphosphines to CpRuCl units by reaction with CpRu(PPh3)(2)Cl. Electrochemical studies of the Ru(II)/Ru(III) couple in Mo-2{mu-SC(pph(2))= C(PPh2)S}(2)Cp-2(RuClCp)(2) (4b) reveals that the two separate ruthenium centers are oxidized electrochemically at different potentials, demonstrating communication between them through the dimolybdenum bis(dithiolene) core. Density functional theory calculations were carried out to explore the electronic structures of these species and to predict and assign their electronic spectra.