Issue Date: March 26, 2012
A Stable Germanone At Last
After chemists tried for more than 100 years, a team has finally synthesized a stable heavy-element version of a ketone—a germanone. Main-group inorganic chemists are celebrating the fundamental achievement because it’s the first time they have made an isolable molecule from a group-14 element below carbon on the periodic table that emulates the carbonyl moiety found in ketones and other important compounds such as aldehydes, esters, and amides.
Researchers led by Tsukasa Matsuo and Kohei Tamao of Japan’s RIKEN Advanced Science Institute pulled off the feat by surrounding a Ge=O bond with a pair of bulky substituents (Nat. Chem., DOI: 10.1038/nchem.1305).
Previous attempts to make carbonyl homologs incorporating silicon, germanium, tin, or lead failed because their highly polarized double bonds to oxygen were too reactive. But over the past decade, inorganic chemists have learned how to use large hydrocarbon substituents to stabilize an array of single- and multiple-bonded heavy-element carbon analogs containing group-13 to group-16 elements. The germanone’s fused-ring substituents with pendant ethyl groups act like a barbed-wire fence to shield the Ge=O bond and inhibit reactivity.
The RIKEN researchers found that the Ge=O bond in the germanone is still highly polarized. And although it’s technically a double bond, the bond order is only 1.25. As a result, the germanone displays reactivity not typical of ordinary ketones. For example, the researchers found that it reacts with water to form a diol and with carbon dioxide to form a cyclic carbonate.
“This synthesis is an important development in the field of multiple bonding involving heavier main-group elements, nicely demonstrating the power of the kinetic stabilization of otherwise highly reactive species,” comments silicon chemist Akira Sekiguchi of the University of Tsukuba, in Japan.
Main-group chemist Philip P. Power of the University of California, Davis, writing in a Nature Chemistry commentary, calls the germanone synthesis “a highly notable event.” Power adds that the door is now open for “what will undoubtedly be a very rich chemistry.”
- Chemical & Engineering News
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