ydride anions, H-, have been found to cause the assembly of dimolybdenurn units [M0(2)(cis-DANF)(2)](2+), DAniF = N,N'-di(p-anisyl)formamidinate, forming a tetranuclear complex [Mo-2(cis-DAniF)(2)](2)(mu-H)(4) (1) with an M0(4)H(4) core that may be described as an elongated tetrahedron in which the H atoms are along the four long edges of such tetrahedron and the M02 units are along the short edges. The two quadruply bonded dimolybdenum units, separated by only 2.718 angstrom, are essentially orthogonal. This gives the shortest [M0(2)]...[M0(2)] distance known for complexes with multiple dimolybdenum units. DFT calculations indicate that the energy of a cuboidal isomer is only 3.8 kcal/ mol above that of 1, but such an isomer has not been observed.