Iron is a junkyard dog among metals-scrappy and hard working. But when it comes to the delicate task of acting as a catalyst in joining together the molecular pieces that make up plastics, chemists have long favored purebreds: exotic metals, such as zirconium. Now, two separate teams of chemists, one at Imperial College and BP Chemicals in London, and the other at the University of North Carolina (UNC) and DuPont, have made iron-based catalysts that excel at making plastics, particularly polyethylene.

The advance could mean a simpler and cheaper way to make common plastics. "They're really good catalysts in making polyethylene very rapidly," says Richard Schrock, a catalyst chemist at MIT. What's more, says Schrock, the catalysts are intriguing because it remains a mystery precisely how and why the iron works.