We report here the syntheses, X-ray crystal structures, electrochemistry, and density functional theory (DFT) single-point calculations of three new complexes: tetrakis(monothiosuccinimidato)dimolybdenum(II) [Mo-2(SNO5)(4), 1a], tetrakis(6-thioxo-2-piperidinonato)dimolybdenum(II) [Mo-2(SNO6)(4), 1b], and chlorotetrakis(monothiosuccinimidato)pyridinelithiumdimolybdenum(II) [pyLiMo(2)(SNO5)(4)Cl, 2-py]. X-ray crystallography shows unusually short axial Mo-2-Cl bond lengths in 2-py, 2.6533(6) angstrom, and dimeric 2-dim, 2.644(1) A, which we propose result from an increased Lewis acidity of the Mo2 unit in the presence of the proximal Li+ ion. When 2-py is dissolved in MeCN, the lithium reversibly dissociates, forming an equilibrium mixture of (MeCNLiMo2(SNO5)(4)Cl) (2-MeCN) and [Li(MeCN)(4)](+)[Mo-2(SNO5)(4)Cl](-) (3). Cyclic voltammetry was used to determine the equilibrium lithium binding constant (room temperature, K-eq = 95 +/- 1). From analysis of the temperature dependence of the equilibrium constant, thermodynamic parameters for the formation of 2-MeCN from 3 (Delta H degrees = -6.96 +/- 0.93 kJ mol(-1) and Delta S degrees = 13.9 +/- 3.5 J mol(-1) K-1) were extracted. DFT calculations indicate that Li+ affects the Mo-Cl bond length through polarization of metal-metal bonding/antibonding molecular orbitals when lithium and chloride are added to the dimolybdenum core.