Scientists Finally Isolate Oxoboranes After 60 Years: The Molecule Chemists Thought Was Impossible
For more than 60 years, chemists around the world tried to capture a molecule called an oxoborane — and failed. The molecule was so unstable that most scientists believed it could never be bottled, studied, or even held still long enough to prove it existed. Now, a team at the University of Würzburg in Germany has done it. The researchers have prepared and isolated not one but three stable oxoboranes, ending one of the longest hunts in modern chemistry.
The discovery was reported in the journal Nature Chemistry on 27 October 2026. It was led by Professor Holger Braunschweig at the University of Würzburg, with computer modelling support from Professor Ashwini K. Phukan’s team at Tezpur University in India. And like many great discoveries in science, it happened partly by accident.
What Is an Oxoborane?
To understand why this matters, it helps to start with the basics. Everything around us is made of atoms, and atoms join together by sharing electrons. These joins are called chemical bonds. A single bond shares one pair of electrons. A double bond shares two pairs. A triple bond shares three pairs — and triple bonds are strong, short, and full of energy.
An oxoborane is a molecule built around a triple bond between two elements: boron and oxygen. Scientists write it as B≡O, where the three lines stand for the triple bond.
Boron is a light element you may know from everyday life. It is found in nature as borax, the mineral used in cleaning products, and in borosilicate glass — the heat-resistant glass used in laboratory beakers and kitchen ovenware. Oxygen is everywhere, in the air we breathe and the water we drink. Boron and oxygen love to bond with each other. In fact, almost all boron chemistry involves boron-oxygen bonds.
But a triple bond between boron and oxygen is a different story. Boron does not like forming triple bonds. And the boron-oxygen triple bond is extremely uneven: oxygen pulls the shared electrons strongly towards itself, leaving the boron end exposed and desperate to react with anything nearby. The result is a molecule that falls apart, rearranges, or grabs onto other molecules almost the moment it forms.
That is why oxoboranes became one of chemistry’s great unsolved puzzles.
A 60-Year Hunt
Chemists have been chasing oxoboranes since at least the early 1960s. Over six decades, researchers from many countries tried again and again to make them.
They came close several times. Scientists detected oxoboranes in the gas phase — as fleeting molecules floating in a vacuum — and trapped them in frozen solids at extremely low temperatures. In one experiment, a simple oxoborane called PhB≡O was observed at just 10 Kelvin, which is about minus 263 degrees Celsius, colder than the dark side of the Moon. Others made “stabilised” versions, where extra chemical groups were attached to the boron or oxygen atoms to calm the molecule down. Those versions could be studied, but they were not true oxoboranes: the extra groups changed the molecule, and every attempt to remove them and free the oxoborane itself failed.
“Nearly everybody in the field had given up on oxoboranes, as they were thought to be just too unstable to be isolated,” said Professor Braunschweig. “So we were stunned to see them spontaneously form in these reactions and stick around long enough that we could study them.”
The Accidental Discovery
The breakthrough began with two doctoral students at Würzburg, Lukas Lubczyk and Christian Markl. They were not trying to make oxoboranes at all. They were studying a highly reactive molecule called a diboracumulene — a compound containing two boron atoms joined together — and testing how it reacted with different ketones. Ketones are common chemicals used in everyday organic chemistry; the best-known example is acetone, the main ingredient in nail polish remover.
Working independently, each student mixed the diboracumulene with a different ketone. And each of them noticed something strange: instead of the expected results, the reactions produced unusual orange or yellow solids.
“The discovery was a pleasant surprise. I never thought the diboracumulene would react the way it did, let alone with multiple different, simple substrates. And when Christian came to me with his compound, I knew we were onto something,” said Lukas Lubczyk.
When the team analysed the strange solids, they realised what they had. Out of many possible outcomes — most of which looked more likely on paper — the reactions had produced oxoboranes as their main products. Not as tiny traces. Not as fleeting intermediates. As the main result, in solid form, sitting in the flask.
How They Did It
The method the Würzburg team discovered is surprisingly simple. They took the diboracumulene and mixed it at room temperature with an excess of a ketone. They tried benzophenone and 4,4′-dimethoxybenzophenone — two ketones commonly found in chemistry laboratories — as well as N,N-dimethylformamide, a chemical widely used as a solvent. In each case, the reaction gave the oxoborane in more than 50 percent yield. That means more than half of the starting material was converted into the target molecule, which is a good result for a difficult synthesis.
Three different oxoboranes were prepared this way. All three were isolated as orange or yellow crystalline solids that are stable at room temperature — a fact that would have seemed impossible to chemists just a few years ago. The three compounds show that the method is not a one-off lucky result but a general route: change the starting ketone, and you get a different oxoborane.
The team also showed that the new molecules can take part in further chemistry. They reacted one oxoborane with amines — a family of chemicals that includes many everyday compounds — and observed two different kinds of reaction, including a simple addition across the boron-oxygen unit. In other words, oxoboranes are not just museum pieces. They can be used as starting materials for new chemistry.
How Scientists Know It Is Real
Extraordinary claims need strong evidence, and the Würzburg team provided it in several independent ways.
First, they used single-crystal X-ray diffraction, a technique that bounces X-rays off a crystal to reveal the exact positions of its atoms. The X-ray results confirmed the identity of all three compounds and showed their structures clearly. The boron-oxygen bonds measured just 1.208 to 1.217 angstroms long. An angstrom is one ten-billionth of a metre. These are among the shortest boron-oxygen bonds ever measured in a stable compound — exactly what you would expect from a triple bond, which pulls atoms closer together than a single or double bond. The boron-oxygen units were also almost perfectly straight, with angles of 174 to 179.5 degrees, close to the 180 degrees of a perfect line. That straightness is another hallmark of a triple bond.
Second, the team measured the infrared spectra of the new compounds. Molecules vibrate, and each type of bond vibrates at a characteristic frequency, like a fingerprint. The boron-oxygen stretching frequencies of the new oxoboranes came out at around 1,860 waves per centimetre — noticeably higher than the roughly 1,600 seen in stabilised oxoborane derivatives, and close to the value measured for a fleeting oxoborane trapped at 10 Kelvin. A higher frequency means a stronger, stiffer bond. The paper concludes that the boron-oxygen bonds in these compounds are probably the strongest ever observed in stable, isolated molecules.
Third, computer calculations carried out by the Tezpur University team matched the experiments. The calculated bond lengths agreed with the X-ray measurements, and the calculations showed two sets of electrons arranged at right angles to each other around the boron-oxygen bond — exactly the pattern expected for a triple bond.
Why Do These Molecules Survive?
The obvious question is: if oxoboranes are so unstable, why do these three survive at room temperature? The answer lies in the chemical group attached to the boron atom.
Each new oxoborane carries a group called a borylenyl group, written as –B(CR2)2. This group is unusually rich in electrons, and it donates electrons towards the boron-oxygen unit. That donation reduces the positive charge sitting on the boron atom, making it less desperate to react with other molecules. The calculations also showed that the empty orbital — the part of the molecule most likely to accept electrons from an attacker — sits at a much higher energy in the stable oxoboranes than in the fleeting ones. That makes the molecule reluctant to react.
Put simply, the borylenyl group acts like a bodyguard. It feeds electrons to the fragile boron-oxygen triple bond and keeps attackers away, so the molecule can sit quietly in a bottle instead of falling apart.
Why It Matters
This is fundamental research. Nobody is going to buy an oxoborane in a shop tomorrow, and the team makes no claim that these molecules will become medicines or materials. But fundamental discoveries like this one matter for three reasons.
First, they open a new field. The Würzburg team says the method could lead to many new oxoboranes, and they are already trying to push it further to prepare other elusive molecules across the periodic table. Every new family of molecules gives chemists new tools — new reagents, new catalysts, and new ways to build the materials and medicines of the future.
Second, they complete a long story. Professor Braunschweig has spent more than 15 years chasing boron triple bonds. In 2012, his team reported the first molecule with a triple bond between two boron atoms. In 2025, they reported the first neutral molecule with a triple bond between boron and carbon. Oxoboranes were the last remaining challenge among the elements in the first row of the periodic table’s p-block. With this result, that set is now complete.
Third, they remind us how science actually works. The discovery was not the result of a grand plan to conquer oxoboranes. It came from two students doing careful experiments, noticing something odd, and following it up. Serendipity — the happy accident — still plays a central role in research, but only when scientists are paying attention.
What Happens Next
The Würzburg team is now testing how far the method can be pushed. The key questions are whether the same trick works with a wider range of starting materials, and whether it can produce other long-sought molecules that chemists have failed to isolate. If the method proves general, it could open the door to a whole new branch of chemistry built around low-coordinate boron-oxygen compounds — molecules in which boron has fewer neighbours than usual, and therefore behaves in unusual and potentially useful ways.
The work was funded by the German Research Foundation (DFG), the German Academic Exchange Service (DAAD), and the Department of Science and Technology of India. The full paper, “Synthesis and isolation of stable oxoboranes”, is published open access in Nature Chemistry, so anyone can read it for free.
For now, the orange and yellow crystals sitting in flasks in Würzburg are the proof of something chemists waited 60 years to see: a molecule that almost everyone had given up on, finally caught, held still, and studied in the open.
Frequently Asked Questions
What is an oxoborane?
An oxoborane is a molecule with a triple bond between a boron atom and an oxygen atom, written as B≡O. Chemists had tried to isolate stable oxoboranes since the early 1960s, but the bond is so reactive that the molecules fell apart before they could be studied.
Who made the discovery?
The work was led by Professor Holger Braunschweig at the University of Würzburg in Germany, with computational support from Professor Ashwini K. Phukan’s group at Tezpur University in India. Doctoral students Lukas Lubczyk and Christian Markl made the key observations. The results were published in Nature Chemistry on 27 October 2026.
How many oxoboranes were made?
Three different stable oxoboranes were prepared and isolated as orange or yellow crystalline solids. Each was made by reacting a molecule called a diboracumulene with a different ketone or amide at room temperature, with yields of more than 50 percent.
Why did it take 60 years?
The boron-oxygen triple bond is extremely polar: oxygen pulls the shared electrons towards itself, leaving the boron atom exposed and highly reactive. Earlier oxoboranes could only be seen in the gas phase or trapped in frozen solids at temperatures near absolute zero. The new method protects the bond with an electron-rich borylenyl group, which calms the boron atom down enough for the molecule to survive at room temperature.
What are oxoboranes used for?
Nothing yet. This is basic research, not a product. But the discovery opens a new area of chemistry. The new molecules can already take part in further reactions, and the method may lead to other elusive molecules and, eventually, new reagents and catalysts.
Is the research freely available?
Yes. The paper “Synthesis and isolation of stable oxoboranes” was published open access in Nature Chemistry on 27 October 2026, so anyone can read the full study without paying.
Sources
- University of Würzburg: https://www.uni-wuerzburg.de/en/news-and-events/news/detail/news/oxoboranes
- Nature Chemistry: https://www.nature.com/articles/s41557-026-02272-w
- ScienceDaily: https://www.sciencedaily.com/releases/2026/11/261103003205.htm
- SciTechDaily: https://scitechdaily.com/nearly-everybody-had-given-up-scientists-finally-solve-a-60-year-chemistry-mystery/
- Bioengineer.org: https://bioengineer.org/chemists-finally-isolate-stable-oxoboranes-after-six-decades-of-failure/
- Newswise: https://www.newswise.com/articles/a-60-year-search-is-over-wurzburg-chemists-isolate-long-elusive-molecules
This article is for general information and education only. It is not legal or financial advice.
