A Rare Dimer of Dimers Having Four Hydride Linkers Joining Two Quadruply Bonded Dimolybdenum Units

Hydride anions, H-, have been found to cause the assembly of dimolybdenum units [Mo2(cis-DAniF)2]2+, DAniF =
N,N‘-di(p-anisyl)formamidinate, forming a tetranuclear complex [Mo2(cis-DAniF)2]2(μ-H)4 (1) with an Mo4H4 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 Mo2 units are along the short edges. The two quadruply bonded dimolybdenum units, separated
by only 2.718 Å, are essentially orthogonal. This gives the shortest [Mo2]···[Mo2] 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.