The Catalyst Review December 2019 - 5

Enzyme Could Inspire a New
Form of "Green" Chemistry...
Scientists at the U.S. Department of
Energy's Brookhaven National Laboratory
have discovered a new function in a plant
enzyme that could have implications for
the design of new chemical catalysts.
"This enzyme could inspire a new form of
'green' chemistry," said Brookhaven Lab
biochemist John Shanklin, who led the
research. The team made the discovery
in the course of their ongoing research
into enzymes that desaturate plant oils.
These desaturase enzymes strip hydrogen
atoms off specific adjacent carbon atoms
in a hydrocarbon chain and insert a double
bond between those carbon atoms.
Shanklin's group had previously created
a triple mutant version of a desaturase
enzyme with interesting properties, and
they were studying the three mutations
separately to see what each one did. Two
of the single mutant enzymes turned out
to remove the double bond between
adjacent carbon atoms and added an
"OH" (hydroxyl group) to each carbon to
produce a fatty acid with two adjacent
hydroxyl groups. Tracing the origins of
the oxygen atoms in the two OH groups
revealed that both came from the same
oxygen molecule. The ability to transfer
both oxygen atoms from a single oxygen
molecule during a reaction, known as
"dioxygenase" chemistry, was something
of a surprise for a "diiron" enzyme (one
with two iron atoms in its active site).
"Dioxygenase chemistry has not previously
been reported for diiron enzymes,"
Shanklin said. "We had to perform some
technically challenging experiments to
provide incontrovertible proof that this
was indeed happening." The team's next
goal is to obtain a crystal structure of
this enzyme using x-rays at the National
Synchrotron Light Source II (NSLS-II).
"We'll share that structural information
with our computational chemistry
colleagues to figure out the details of how
this unprecedented chemistry can occur
with this class of catalyst." That work
could help the team learn how to control
the configuration of lab-made catalysts to
mimic the plant-derived version. Source:
Technology Networks, 12/10/2019.
The Catalyst Review 										

Nickel Catalyst Fends Off Air Attack...
Nickel catalysts have shot to synthetic stardom over the past decade or so, proving
particularly useful in coupling reactions that form carbon-carbon or carbon-nitrogen
bonds. The most popular catalyst for these reactions is bis(1,5-cyclooctadiene)
nickel (Ni(COD)2), and although it's very effective, the complex decomposes rapidly
in air, making it troublesome to use. Researchers at the Max Planck Institute for Coal
Research have now developed an air-stable alternative to Ni(COD)2 that could make
nickel catalysis much more accessible to users. Nickel is increasingly used in reactions
traditionally dominated by palladium catalysts.
The nickel catalysts used in these reactions are
often extremely reactive, so they must be freshly
generated within the reaction mixture. Chemists
do this by mixing a precatalyst like Ni(COD)2 with
other ligands, such as phosphines or bipyridines,
which take the place of cyclooctadiene to form the
active catalyst. The new precatalyst is based on a
nickel atom surrounded by three stilbene ligands
that bear trifluoromethyl groups (Ni(Fstb)3).
Trifluoromethyl-bearing stilbene ligands
These ligands enclose the nickel and protect it
wrap nickel in a protective cloak. Green =
from oxygen. "People will use this immediately
Ni; dark grey = C; light grey = H; yellow = F.
because it's a drop-in replacement," for Ni(COD)2, Credit: Nature Catalysis
says Nilay Hazari of Yale University, who develops
transition metal catalysts. "In my mind, it's a very significant step forward." The Max
Planck researchers used Ni(Fstb)3 to generate active catalysts in more than a dozen
different reactions, including classics such as a Suzuki-Miyaura coupling, BuchwaldHartwig carbon-nitrogen bond formations, and a Heck reaction. It generally performed
as well as Ni(COD)2, giving the intended products in high yields. Source: Chemical &
Engineering News (C&EN), 12/9/2019.
CMU Becomes Go-To Place for Machine Learning in Catalysis
The Department of Energy (DOE) and the National Science Foundation (NSF) have
invested in the unique research that Professors Zachary Ulissi, John Kitchin, and Andrew
Gellman of Carnegie Mellon University (CMU) are pioneering, which looks into the role
that machine learning can play in the discovery of new catalysts. Kitchin, with support
from the NSF, has developed a unique machine learning algorithm to rapidly test as
many combinations of metal alloys for hydrogen fuel cells as possible. "Our research
has developed a unique machine learning algorithm to simulate the composition
of a surface so that we can estimate and determine the atomic-scale distribution of
atoms in the surface," Kitchin says. Ulissi, along with his collaborators at Penn State,
are working to develop a computational tool that uses machine learning to not only
model intermetallic configurations and test them for efficiency, but uses the data
gathered from these experiments to decide what configurations are more likely to work
in the future. The research is supported by a $1.2 million-dollar grant from the U.S.
Department of Energy. Gellman and his research group have developed experimental
methods to complement the machine learning tools developed by Kitchin and Ulissi.
The National Science Foundation, through its Designing Materials to Revolutionize
and Engineer Our Future (DMREF) initiative, has invested in a team led by Gellman to
pioneer brand-new research tools, which can prepare hundreds of alloy compositions
simultaneously and concurrently analyze their surfaces. Source: Carnegie Mellon
University, 12/3/2019.

December 2019



The Catalyst Review December 2019

Table of Contents for the Digital Edition of The Catalyst Review December 2019

The Catalyst Review December 2019 - cover
The Catalyst Review December 2019 - contents
The Catalyst Review December 2019 - 1
The Catalyst Review December 2019 - 2
The Catalyst Review December 2019 - 3
The Catalyst Review December 2019 - 4
The Catalyst Review December 2019 - 5
The Catalyst Review December 2019 - 6
The Catalyst Review December 2019 - 7
The Catalyst Review December 2019 - 8
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