Metal Dihydrogen and O-Bond Complexes

The synthesis and characterization of fascinating new molecules that could not have been imagined to be stable lie at the heart of chemistry. The Nobel Prize-winning discovery of buckminsterfullerene is a perfect example of thecharm and beauty of chemistry, which even nonscientists can appreciate.However, there are relatively few such paradigm-shifting discoveries or new bonding concepts that we all remember from our early science courses. A technologicalexample from when I was a freshman at Case Western Reserve University in the early 1960s was the laser, for which the potential uses were initially vastly underestimated. In 1965 the first complex of “inert” dinitrogen was reported by Allen and Senoff, and there is a remarkable parallel with our even more unexpected discovery ofdihydrogen complexes nearly 20 years later. I also well remember learning about the “banana-bond” representing the 3c-2e bonding inelectron-deficient boron hydrides such as diborane. This multicenter “nonclassical” chemical bonding first described by Longuet-Higgins and later by Lipscomb had a very important role in the development of valence theory and initially had only a few prominent members: boranes and hydride- and alkyl-bridged metal complexes.