ttatmaaafflftfe INORGANIC
CHEMISTRY
'TROPHY' COMPLEX Neutral N 2 ligand is bound end-on to a single uranium metal center CROWDED In (C5Me5)3U(N2)pthe U-N bond is at right angles to the ring centroid-U bonds.
BONDSMEN Evans (from left), Kozimor, and Ziller prepared and characterized a new type of uraniumdinitrogen complex.
A
NEW TWI ST ON THE CHEM-
istry of uranium and dinitrogen (N2) has been revealed by researchers at the University of California, Irvine. They have found that a simple complex of uranium, ^ M e ^ U ,
can be forced, under pressure, to take on what for an actinide is an unlikely ligand—neutral N2— and bind it end-on \J.Am. Chem. Soc, 125,14264 (2003)}. The resulting metal complex, ^ M e ^ l K N ^ , is afirstin several respects, says chemistry professor WilliamJ. Evans, who led the research effort. Terminal end-on binding of N 2 to transition metals is well documented, Evans and coworkers Stosh A. Kozimor and Joseph W Ziller note in their pa-
per. But, to their knowledge, it has never before been observed in complexes of an f element (an element having an f orbital—that is, a lanthanide or actinide). In the three uranium-N2 complexes reported previously, either two uranium atoms or a uranium and a molybdenum atom are bridged by the anionic (N^ 2- ligand. Thus, the new U-N2 complex "appears to be thefirstmonometallic f element complex ofN 2 of any kind," the team points out. "Part of the significance of this discovery is that dinitrogen may coordinate to felements (and possibly other electropositive elements) to a greater extent than previously thought," Evans tells C&EN. Most f-element reactions are run under dinitrogen because chemists assume that it is an inert atmosphere. "Perhaps it is not inert in all cases," he suggests. For example, if N 2 blocks a coordination position in an f-element complex, it could affect the chemistry "These results are surprising in another way," Evans continues. "It is unexpected that the extremely sterically crowded mole-
cule ^ M e ^ U would even {accept} another ligand." To force it to take on dinitrogen, Kozimor subjected the complex, in solution, to 80 psi of nitrogen gas, which led to the formation of crystals of the U-N2 complex. "It is remarkable," Evans says, that the crowded metal center binds another ligand of any type—particularly neutral N2, which has little affinity for the usually highly ionic f elements. The ^ M e ^ U precursor is so crowded that when the dinitrogen is added, the positions ofthe three C5Me5 ligands do not change— "they probably have no room to move," Evans says. As a result, the N2-containing product has an unusual structure in which the U-N bond is atrightangles to the bonds formed between U and the center of the C5Me5 rings. Other inorganic chemists are equally enthusiastic about Evans' creation. "I think this is a spectacular molecule [that] raises fundamental questions on structure and bonding," comments professor Geoff Cloke of the University of Sussex, in England. And professor Michael D. Fryzuk of the University of British Columbia, Vancouver, hails the complex as "a remarkable trophy in dinitrogen coordination chemistry" The work could help lead to insights into nitrogen fixation, Evans says.—RON DAG AN I
BUSINESS
Huntsman To Make Cutsp Improve Liquidity he Huntsman group of companies will undertake a $200 million cost-cutting program over the next 18 months, with site consolidations and employee reductions to be announced soon. "The severe economic slump the chemical industry has been experiencing for the last three years continues unabated," says Peter R. Huntsman, president and CEO of the Huntsman companies. It offers, he adds, "an opportunity to reposition our businesses at the bottom of the cycle to ensure their long-term competitiveness and profitability." Each of six Huntsman chemical businesses has plans to help meet the overall minimum $200 million goal. The intention, Huntsman explains, is to manage the businesses so they can
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pay down debt, make interest payments, and invest in new projects. To do just that at this time last year, the Huntsman group cut a deal with its largest bondholder, handing over 49% of the company in exchange for eliminating $775 million in debt. On a positive note, earnings for the Huntsman group stabilized between the second and third quarters. Third-quarter earnings before interest, taxes, depreciation, and amortization were $170 million, including $10.7 million in restructuring and other charges, compared with $136 million in the second quarter, including $53.7 million in charges. Revenues for the third quarter were up 8.9%, compared with 2002, to $2.30 billion, and they gained 15% over nine months to hit $6.88 billion, with the six businesses all posting growth in sales.—ANN THAYER
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