A rhodium-based catalyst for making organosilicon using less precious metal

June 21, 2017, Tokyo Institute of Technology
A view of the hydrosilylation reaction using the SiO2-supported catalyst consisting of an immobilised Rh complex and tertiary amines, with a turnover of 260 (left) and approaching 1,900,000 (right). The very low loading of Rh was well presented by the clear solution (right). Credit: Tokyo Institute of Technology

The design of new catalysts is essential for making new and useful organosilicon compounds, which are in high demand in fields ranging from the medical to the electronics industries. A crucial step in this process is hydrosilylation (the formation of carbon-silicon bonds), and much interest has focused on rhodium-based catalysts known to be effective in accelerating this reaction.

Now, Ken Motokura of Tokyo Institute of technology (Tokyo Tech) and colleagues have devised a new consisting of three core components—a (Rh) complex and a tertiary amine (NEt2) on silica (SiO2)—that significantly improves the hydrosilylation process.

Reported in ACS Catalysis, the new catalyst achieved a turnover number of approximately 1,900,000 over a period of 24 hours, far surpassing other supported-rhodium catalysts developed to date.

The co-immobilised amine (NEt2) is thought to be a key factor behind the improved catalytic activity. "Although the specific reason for improvement is still unclear, we know that usually the hydrosilylation reaction is accelerated by electron donation to the rhodium center, and the tertiary amine has electron-donating ability," says Motokura. The work builds on the research group's previous finding that co-immobilization of two active sites enhances catalysis drastically.

The new study demonstrates that having both the Rh complex and amine on the SiO2 surface produces a greater yield (96%) than with just Rh (9%) or just amine (less than 1%), suggesting a synergistic effect at play.

Notably, the order in which the Rh complex and amine were immobilised affected . Motokura explains that the timing of immobilisation may affect the positioning of the Rh complex and amine, which ultimately affects catalytic activity. This finding concurs with a previous study by the same team, which found that strongly depended on the proximity of the Rh complex and tertiary amine.

One limiting factor for future studies is the high cost of rhodium. "In this study, it's important to note that we were able to achieve very low loading of rhodium," says Motokura. "We recognise that finding alternatives to rhodium will be critical. So far, however, catalysts based on inexpensive metals generally show low activity."

The team's next goal is to produce a using non-precious metal and organic functions on the same surface, in order to achieve catalytic performance on par with rhodium-based catalysts. Motokura says: "If this succeeds, our long-held goal of developing sustainable solutions based on chemistry will be realized."

Explore further: Catalytic system makes the synthesis of bioactive molecules easier

More information: Ken Motokura et al, SiO-Supported Rh Catalyst for Efficient Hydrosilylation of Olefins Improved by Simultaneously Immobilized Tertiary Amines, ACS Catalysis (2017). DOI: 10.1021/acscatal.7b01523

Related Stories

New method for activating Earth-abundant metal catalysts

January 31, 2017

(Phys.org)—Many industrially relevant reactions require either a precious metal catalyst or an Earth-abundant metal catalyst in a low oxidation state. A catalyst with a Fe(0) complex, for example, is a good catalyst for ...

Recommended for you

Scientists bring polymers into atomic-scale focus

November 12, 2018

From water bottles and food containers to toys and tubing, many modern materials are made of plastics. And while we produce about 110 million tons per year of synthetic polymers like polyethylene and polypropylene worldwide ...

Nitrogen fixation in ambient conditions

November 12, 2018

Abundant in the atmosphere, nitrogen is rarely used in the industrial production of chemicals. The most important process using nitrogen is the synthesis of ammonia used for the preparation of agricultural fertilizers.

New catalyst turns pollutant into fuel

November 12, 2018

Rather than allow power plants and industry to toss carbon dioxide into the atmosphere, incoming Rice University assistant professor Haotian Wang has a plan to convert the greenhouse gas into useful products in a green way.

Bending DNA costs less energy than assumed

November 12, 2018

The way DNA folds largely determines which genes are read out. John van Noort and his group have quantified how easily rolled-up DNA parts stack. This costs less energy than previously assumed. Publication in Biophysical ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.