NEWS OF THE WEEK
TWO’S A CHARM FOR NICKEL COMPLEX ORGANOMETALLICS: Low-coordinate
nickel species presents intriguing electronic structure and reactivity
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MULTI-INSTITUTION research team has pre-
pared the first two-coordinate transition-metal complex containing an imido ligand. This coordinatively unsaturated nickel(II) complex demonstrates enhanced chemical reactivity over more highly coordinated complexes and potentially signals a new facet of research for organometallic chemists. The active versions of transition-metal complexes in many chemical reactions, such as olefin metathesis and the reduction of nitrogen to ammonia, contain multiple bonds between a metal with a vacant d orbital and a ligand with abundant electron density. But chemists struggle to re-create these reactive intermediates as isolable molecules. In a new study, Carl A. Laskowski and Gregory L. Hillhouse of the University of Chicago and coworkers show one way to do it: They pair nickel with an extremely bulky imidazole N-
OVERSIGHT GALORE IN NEW CONGRESS POLITICS: Republicans taking
control of House vow close scrutiny of federal actions
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Boehner takes the gavel and charge of the House.
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VEN BEFORE THE 112th Congress was sworn in
last week, Republicans in the House of Representatives made clear their intent to provide rigorous oversight of government activities—from recalls by FDA, to greenhouse gas emissions regulations by EPA, to programs contained in the reauthorization of the America Competes Act. The watchdog fervor, expected to give rise to a flurry of investigations, is part of the GOP’s pledge to cut federal spending and to identify and change programs and regulations that Republicans believe kill jobs. To help with the latter objective, House Committee on Oversight & Government Reform Chairman Darrell E. Issa (R-Calif.) sent letters last month to 150 trade associations, companies, and think tanks asking them to identify regulations that negatively impact job creation. Numerous chemical companies and trade WWW.CEN-ONLINE.ORG
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heterocyclic carbene ligand on one side and a bulky terphenyl imido ligand on the other (J. Am. Chem. Soc., DOI: 10.1021/ja1101213). The “massive steric profile” of the imidazole helps prevent more than two ligands from accessing the nickel, Hillhouse notes. As a result, the complex adjusts its electronic structure by forming a linear C–Ni=N core dominated by π-bonding. The nickel atom features a “high spin” d8 electron configuration with two unpaired electrons, whereas most two-coordinate transitionmetal complexes have a paired d10 electron configuration. Study coauthor Thomas R. Cundari of the University of North Texas confirmed these experimental findings with density functional theory calculations. Reactive substrates such as carbon monoxide and ethylene readily add across the Ni=N bond, resulting in the transfer of the imido group to the substrate to form isocyanates and vinylamines, respectively. This reactivity is greatly enhanced relative to three-coordinate nickel imido complexes, Hillhouse says. “This piece of work illustrates a new way to effect the catalytic synthesis of organonitrogen compounds,” says Christopher C. Cummins of Massachusetts Institute of Technology, whose group focuses on using large ligands to make low-coordinate complexes. “The two-coordinate nickel imido catalyst itself represents a breakthrough in the chemistry of nickel,” Cummins adds, “and the simplicity of the transfer reaction system renders it amenable to a high degree of mechanistic analysis.”—STEVE RITTER
groups received letters and are expected to respond. For instance, a spokeswoman for the Society of Chemical Manufacturers & Affiliates says SOCMA received Issa’s letter. After canvassing its membership of custom and specialty chemical companies, the trade group plans to identify problematic regulations such as EPA’s final rule on the definition of solid waste and the agency’s rule on maximum achievable control technology for boilers. House committees have also announced oversight investigations to improve government accountability, reduce excess spending, and remove economic stumbling blocks. Issa announced that his committee will tackle six major investigations—including a look at recalls by FDA—in the next three months. The Science & Technology Committee pledged to scrutinize the programs authorized by the just-signed-into-law America Competes Act reauthorization, and the Energy & Commerce Committee vowed to investigate EPA’s plan to regulate greenhouse gases. “EPA has its foot firmly on the throat of our economic recovery,” Energy & Commerce Chairman Fred S. Upton (R-Mich.), said in a statement. “We will not allow the Administration to regulate what they have been unable to legislate.” “Our aim will be to give government back to the people,” said the newly elected Speaker of the House, John A. Boehner (R-Ohio).—SUSAN MORRISSEY
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