Four new quadruply-bonded dimolybdenum(II) complexes of the formula Mo2Cl4(NH2R)(4) (R = Et (1), Pr-n (2), Bu-t (3), Cy (4)) have been prepared in excellent yield by reduction of the dimolybdenum(III) complex MO2Cl6(THF)(3) with 2 equiv of sodium amalgam in the presence of the appropriate primary amine. The molecular structures of 2-4 have been investigated by X-ray crystallography. Crystal data are as follows: for 2, orthorhombic space group Ccca with a = 13.328(3) Angstrom, b = 26.639(5) Angstrom, c = 6.774(2) Angstrom, and Z = 4; for 3, monoclinic space group P2(1)/c with a = 19.165(1) Angstrom, b = 20.858(1) Angstrom, c = 14.1400(8) Angstrom, beta = 99.002(5)degrees, and Z = 8; for 4, tetragonal space group P4(2)2(1)2 with a 15.556(4) Angstrom, c = 6.9368(8) Angstrom, and Z = 2. All of the non-centrosymmetric molecules 2-4 possess the same structure characterized by a Mo2Cl4N4 core with D-2d virtual symmetry and slight deviation from the eclipsed geometry. The Mo-Mo bond lengths for 2, 3, and 4 are 2.118(2), 2.1322(6), and 2.117(1) Angstrom, respectively, which are consistent with the Mo-Mo quadruple bond. In addition to the structural data, IR, UV-vis, and H-1 NMR spectroscopy have been used to characterize the complexes 1-4. Without amalgam, the reactions of the starting material with amines also produce the reduced species but with low yields (not exceeding 25%). The main products of these interactions have been found to be mononuclear molybdenum(III) complexes MoCl3(NH2R)(3) This has been confirmed by a single-crystal X-ray diffraction study for mer-MoCl3(NH2Prn)(3). 1/6THF (2a(.)1/6THF) with the following crystal data: triclinic space group P (1) over bar, a = 12.370(2) Angstrom, b = 17.977(2) Angstrom, c = 25.498(6) Angstrom, alpha = 95.32(1)degrees, beta = 103.21(2)degrees, gamma = 103.48(1)degrees, and Z = 12.