Together and apart.

Chemists report the first chemical reaction that can split apart and recombine the two atoms in molecular hydrogen without using an expensive metal catalyst.

Hydrogen gas is a widely used reagent in the petrochemical and pharmaceutical industries. Precious-metal catalysts break the tight bond between the two hydrogen atoms in the gas, freeing them to move to various other molecules.

A few nonmetals can break up hydrogen gas, but only metals can also reassemble two hydrogen atoms into the gas, a reaction relevant to hydrogen-fuel production and storage.

In the Nov. 17 Science, Douglas W. Stephan of the University of Windsor in Ontario and his colleagues describe a metalfree compound, called phosphonium borate, that does both. When the researchers heated a solution of the compound to a little over 100[degrees]C, it released two of its hydrogen atoms as hydrogen gas. By bubbling the gas back through the same solution at room temperature, the researchers then broke up the hydrogen atoms, each of which reattached to phosphonium borate.

In the case of hydrogen storage, researchers are still looking for a system that can easily liberate hydrogen and take it back up. Although phosphonium borate doesn't store much hydrogen, "it might be possible to use our compound as a catalyst to add hydrogen" to another material with abundant storage capacity, Stephan says.--A.C.