Goldrich, a member of the court-appointed committee representing women claimants, says Dow Coming's offer is "inadequate and unfair." She adds, "This proposal leaves many women having to pay out of their own pockets to clean up the damage Dow Corning did in their bodies." Dow Corning says the bankruptcy judge could approve its plan by the middle of 1998 after hearings are held. Following the judge's approval, claimants and commercial creditors would have an opportunity to vote on the former implant maker's plan. Marc Reisch
Zeolite-type crystals incorporate cobalt Using a design technique known as charge-matching, chemists at the University of California, Santa Barbara, have synthesized dozens of cobalt-rich zeolite-type crystals. The new materials have the potential to expand the already rich range of zeolites' uses in catalysis and gas separation. The experiments were conducted by Galen D. Stucky, professor in the departments of chemistry and materials, and graduate student Pingyun Feng and X-ray crystallographer Xianhui Bu [Nature, 388,735(1997)]. The cagelike frames of zeolites enclose molecular-sized cavities. The porous materials belong to the aluminosilicate family and are known in both natural and synthetic forms. Researchers have long tried to prepare zeolite-type materials in which aluminum atoms are replaced with transition-metal atoms. The wide variety of oxi-
Stucky: new materials with zeolite structure
ACP-1, a proposed but never before observed cobalt phosphate-based zeolite analog, forms crystals with double four-ring units. Phosphorus sites are shown In red and cobalt (or aluminum) in yellow.
dation states and other chemical properties available to transition metals—relative to aluminum—is expected to result in new materials with a number of useful characteristics, such as a broader range of reactions that can be catalyzed. Transition metals have previously been incorporated into some zeolite analogs, particularly in the aluminophosphate series. But the number of aluminum sites replaced with transition-metal atoms in that family of compounds has not exceeded 38%, according to the UC Santa Baibara chemists. Stucky's group, however, now reports preparing many cobalt phosphatebased zeolite counterparts—some with cobalt concentrations near 90%. "We've collected a vast amount of structural information that's proving very useful in understanding the fundamentals of zeolite synthesis," Stucky says. "The significance of this work is not just that we've made a collection of new zeolite analogs. Rather it's a general synthesis procedure that can lead to the preparation of untold numbers of useful materials." In an accompanying commentary in Nature, Robert L. Bedard of the UOP Research Center, Des Plains, 111., describes Stucky's new procedure as "clever." But, he adds, whether the "route is more generally applicable to other divalent transition metals is not yet clear." The strategy for synthesizing crystals with zeolite structure, Feng explains, is to match the charge and shape of the framework cavity—the host—with an appropriate filler material—the guest. The host's features are varied by adjusting the ratio of divalent cobalt ions to trivalent aluminum ions. The charge-to-volume ratio of the guests—which in the present study are al-
kyl ammonium ions—is controlled by the size and shape of the alkyl groups and the number of charged nitrogen atoms. Through a series of modifications to host and guest—while ensuring that both are appropriately charge- and shapematched—the Santa Barbara researchers synthesized a large group of cobalt phosphate-based zeolite analogs. Some of the new crystals possess structures previously seen only in nature. Some of the products even have structures that were proposed theoretically but never observed—from natural or synthetic sources. By uncovering the details of the interaction between organic guests and an inorganic framework, Stucky aims to prepare zeolite analogs in which pore size, framework charge, and magnetic and redox properties are tightly controlled. Such materials, he says, will lead to very efficient separations and high catalytic selectivity. Mitch Jacoby
Perkin-Elmer buys line of drug reagents and instruments Perkin-Elmer Corp., Norwalk, Conn., has agreed to acquire PerSeptive Biosystems, Framingham, Mass., for $13 per share, or about $360 million—a premium for a startup company that lost $50 million on sales of $76 million in its fiscal 1996, which ended last Sept. 30. PerSeptive's main attraction for Perkin-Elmer is its line of proprietary instruments and reagents for peptide and oligonucleotide synthesis, purification, and sequencing—valuable tools for drug discovery and production. "This merger will enhance our position as an effective provider of innovative, integrated platforms enabling our customers to be more efficient and cost-effective in bringing new pharmaceuticals to market," says Perkin-Elmer's president, chairman, and chief executive officer, Tony L. White. And it will allow PerSeptive, which has been tightly focused on development since its founding in 1990, to continue to pursue those efforts without worrying about finances. "I think it's a good deal for both of them," says equity analyst Eddie Hedaya of BioVest Research, Hartsdale, N.Y., an investment research firm specializing in biotechnology and health care. "It helps Perkin-Elmer's life sciences program and provides them with valuable technical reSEPTEMBER 1, 1997 C&EN 11
