Hydridotris(pyrazolyl)borate Ruthenium(II) Complexes Containing Phosphine or Phosphite Ligands
Jocelyn Lanorio, Illinois College
Location: Illinois
Abstract
This course-based research will introduce students in an advanced inorganic chemistry course to air-sensitive chemistry and catalysis. Students will prepare and examine a series of ruthenium(II) hydridotris(pyrazolyl)borato complexes with phosphine or phosphite ligands using modern instrumentation and specialized equipment such as Schlenk line and drybox. The first two meetings will be devoted to literature searches, introduction/familiarization of instrument operation, and selection of phosphine or phosphite ligand along with student submitting proposal that contains the safety protocols and handling of the chemicals involved in their selected system. Four meetings will then be designated for the synthesis and characterization of the complex. The students run catalytic and control reactions and determine the percent yield of the product using 1H NMR during the last two meetings of the course. The synthesis and catalytic conditions are modified from previously published research article.
This experiment combines complex synthesis, characterization, data analysis, data sharing and presentation.
Student Goals
- Design controlled experiments using the literature and include plans for analyzing the data.
- Make evidence-based arguments using your own and others' findings and draw appropriate conclusions.
- Use of appropriate language and style to communicate research progress orally and in writing.
Research Goals
- Synthesize and characterize a series of ruthenium(II) phosphine or phosphite complexes with hydridotris(pyrazolyl)borate (Tp) as ancillary ligand.
- Investigate the efficiency of synthesized complexes in atom transfer reaction.
Context
Advanced Inorganic Chemistry (CH 332) course at Illinois College is mainly composed of chemistry and biochemistry majors. This CURE should be full semester (Full CURE, cCURE) and students should have finished a two-semester organic chemistry. The ideal class size should be at most 12 students (or 6 groups) due to the cost of ruthenium complex and the need for use of Schlenk line and drybox. Students should have fundamental wet-chemistry skills and familiarity of the NMR operation and interpretation.
Target Audience:Major, Upper Division
CURE Duration: A few class periods, A full term, Half a term
CURE Design
The research theme is centered around the preparation, properties, and a selected catalytic application of ruthenium(II) phosphine or phosphite with an ancillary ligand hydridotris(pyrazolyl)borate. Most of the synthetic reactions should be performed under inert conditions due to the air sensitive nature of intermediate species. There would be a high probability that groups need to run numerous attempts to make their selected systems. This CURE is designed to expose students to literature search, system proposal, and conducting experiments in iterative manners. Instructor can provide a list of phosphines and phosphites that are air-stable and easy to handle. This CURE will also highlight the importance of collaboration or sharing/comparing each other's findings in order to make evidence-based arguments and conclusions (e.g. effect of sterics and electron donating ability of phosphine/ligand).
Instructor should list course prerequisites, provide a clear set of expected skills and knowledge, train students with the use of Schlenk line/drybox and microscale chemistry.
The stakeholders are researchers who use ruthenium(II) phosphine/phosphite complexes for catalysis.
Core Competencies:Analyzing and interpreting data, Constructing explanations (for science) and designing solutions (for engineering), Planning and carrying out investigations
Nature of Research:Basic Research, Wet Lab/Bench Research
Tasks that Align Student and Research Goals
Research Goals →
Student Goals ↓
Research Goal 1: Synthesize and characterize a series of ruthenium(II) phosphine or phosphite complexes with hydridotris(pyrazolyl)borate (Tp) as ancillary ligand.
Research Goal 2: Investigate the efficiency of synthesized complexes in atom transfer reaction.
Student Goal 1: Design controlled experiments using the literature and include plans for analyzing the data.
Use database to find current, general knowledge about hydridotris(pyrazolyl)borate (Tp) metal complexes and ruthenium(II) phosphine/phosphite complexes.
Distinguish between primary and secondary literature.
Create an annotated bibliography of 6 primary lit papers most relevant to our research goal.
Explain the ongoing interest regarding Tp ligand.
Select and describe the phospine or phosphite ligand to use from a given list.
Distinguish monodentate versus bidentate ligands and assess possibility of having more than one desired TpRu complex (example: mixed phosphine or bisphosphine).
Identify at least 2 traditional/general synthetic routes to try for selected TpRu(II) phosphine system.
Propose synthetic procedure to follow and define the conditions of reaction(s).
Prepare list of reagents needed including safety and handling of chemicals.
Synthesize the proposed complex using Schlenk techniques.
Use appropriate equipment and modern instrumentation (1H, 13C, 31P) to characterize the selected complex.
Analyze data from each experiment and draw conclusions regarding the completion of reaction and need of further characterization techniques (example: use 19F for fluorinated phosphine? 11B?)
Define atom transfer reaction.
Describe the mechanism of traditional ruthenium complex in atom transfer reaction.
Execute traditional ruthenium-catalyzed atom transfer reaction.
Define a control reaction(s).
Define metrics (such as % conversion, TON, TOF calculation) to be used for assessing efficiency of the complex.
Use 1H NMR to follow catalysis reaction.
Assess need for further monitoring of reaction and/or characterization of product.
Student Goal 2: Make evidence-based arguments using your own and others' findings and draw appropriate conclusions.
Summarize the status of experiment.
Make and defend a claim about the current status of an experiment (did you get the compound? Is it pure?)
Provide alternative methodology in case proposed reaction(s) fail and provide reasons for the modification.
Summarize the status of catalysis.
Assess the efficiency of the catalyst using standard calculations and procedures (e.g. % conversion and TON calculation).
Compare catalytic efficiency to literature values for similar reactions and to those obtained by other groups.
Optimize reaction conditions or propose an optimal ligand and conditions appropriate to the selected reaction.
Student Goal 3: Use of appropriate language and style to communicate research progress orally and in writing.
Make regular, individual notebook entries.
Discuss the group project with other groups.
Write a report regarding current stage of the project, what has been completed, the challenges, and recommendations.
Present results in class orally. All presentations should utilize "PowerPoint" or similar presentation software.
Make regular, individual notebook entries.
Discuss the catalysis results with other groups.
Write a report regarding current stage of the project, what has been completed, the challenges, and recommendations.
Present results in class orally. All presentations should utilize "PowerPoint" or similar presentation software.
Instructional Materials
Necessary equipment and supplies:
Standard lab equipment/glassware
Schlenk line
Drybox
FT-NMR with multinuclear capability
ruthenium chloride trihydrate
Potassium hydrotris(1-pyrazolyl)borate
A review article about hydrotris(pyrazolyl)borate (Tp) complexes is provided.1 An air-stable atom transfer radical addition of carbon tetrachloride and chlorinated esters to various olefins2 by similar type of complexes can be adopted for research goal 2. The synthetic procedure for TpRu(PPh3)2Cl complex is also provided.3 The complex TpRu(PPh3)2Cl is a synthon for other TpRu(PR3)2X complexes.
Proposed Schedule (Microsoft Word 2007 (.docx) 15kB Jul10 19)
Assessment
Written Paper Grading Rubric (Acrobat (PDF) 76kB Jul10 19)
Presentation Grading Rubric (Acrobat (PDF) 42kB Jul10 19)
Instructional Staffing
A single instructor runs the course with an undergraduate lab TA. Ideally, instructor should meet with the lab TA prior to each meeting of the CURE course to provide necessary trainings with operation of specialized equipment.
Author Experience
Jocelyn Lanorio, Illinois College
One of my goals as an educator is to broaden participation of students to research by providing them easy access to it via my classes. Advanced Inorganic Chemistry course (CH 332) at Illinois College is typically composed of 5-6 students (though capacity is up to 12 students) and would be an ideal platform for providing extensive tools and knowledge about research. Through this CURE, students will have experience in working with inert atmosphere systems, as well as exposure to catalysis in the laboratory.
Advice for Implementation
[If you have already taught using this CURE, what have you learned in the experience that would be of help to someone else trying to do it? What are some common questions and student sticking points and how did you overcome them? Are there particular equipment or supply needs or other costs to keep in mind for implementing the CURE?]
Iteration
[How are students involved in trouble-shooting, problem-solving, or repeating aspects of their work? What opportunities do students have to "fail" scientifically and learn and take action as a result? How is time spent in the CURE structured to allow for research to not go as planned?]
The challenges that students face in this course is the possibility of decomposition of intermediate complexes upon exposure to air and/or moisture. It will be useful for the instructor to degass and dry solvents prior to labs. Students also need to work with microscale amounts to allow multiple reactions runs.
This CURE can be easily modified by assigning students to select another (or a series of) ancillary ligand instead of the specific hydridotris(pyrazolyl)borate (Tp). Another modification can be selecting another catalysis reaction for the application of a series of Ru(II) complexes. A higher level modification will be assigning students to pick their own catalytic reaction.
Using CURE Data
Student data will be contributed to an on campus poster presentation at Illinois College and to the national ACS poster presentation. Each group will compare the catalytic efficiency of their synthesized complex to literature values for similar reactions and to those obtained by other students to make sure that their values are reasonable. The synthetic and catalytic procedures will be run at least twice to ensure reproducibility. Data quality will be assessed by the instructor. If needed, experiments can be repeated by undergraduate researchers enrolled in the independent research courses CH 465/466. The ultimate goal is to publish the collected data from this CURE.
Resources
- Trofimenko, S. Recent Advances in Poly(Pyrazolyl)Borate (Scorpionate) Chemistry. Chem. Rev. 1993, 93 (3), 943–980. https://doi.org/10.1021/cr00019a006.
- Nair, R.P.; Pineda Lanorio, J. A.; Frost, B. J. Atom transfer radical addition (ATRA) of carbon tetrachloride and chlorinated esters to various olefins catalyzed by Cp'Ru(PPh3)(PR3)Cl complexes. Inorganica Chimica Acta, 15 January 2012, 380, 96-103. https://doi.org/10.1016/j.ica.2011.11.008.
- Foley, N. A.; Abernethy, R. J.; Gunnoe, T. B.; Hill, A. F.; Boyle, P. D.; Sabat, M. Chlorination of Boron on a Ruthenium-Coordinated Hydridotris(Pyrazolyl)Borate (Tp) Ligand: A Caveat for the Use of TpRu(PPh3)2 Cl. Organometallics 2009, 28 (1), 374–377. https://doi.org/10.1021/om8008074.
Strengths:
I love how you integrate safety into the curriculum
It is great that students get a choice in which ligands to test
I’ve seen very few inorganic CUREs, so it will be really powerful to get this out to the community!
Suggestions:
In research goal 2 x student goal 2 objectives – it might be helpful to have them compare their catalytic efficiency to literature values for similar reactions or to those obtained by other students. This will help them determine if their values seem reasonable, or highlight if they might have made an error in their experimental setup or data analysis.
For student goal 3, maybe provide a bit more detail about how they present in class. For example, is it a 5 min power point presentation vs 10 min chalk talk?
Consider also including information in your instructional materials about how they communicate their results. A copy of your syllabus would probably include this.
Questions:
In the iteration, how do you deal with failed synthesis of a complex? Is there a way to figure out whether the students made an error and need to try again vs that complex is just not stable enough to be isolated?
Is your goal to publish these data? If so, you will want to consider how you balance giving students the choice of ligands vs making sure they cover the needed scope to put together a story for publication.
Feasibility:
This seems very feasible to complete in a semester, or even part of a semester, and it is great how synthesis and testing of the complexes can be divided over multiple semesters to build a bigger project. This also seems to have a ton of space for expansion and iteration by investigating other metals and ligands.
14081:42062
Share
edittextuser=112414 post_id=42062 initial_post_id=0 thread_id=14081
Strength:
I really like the written report rubric. It makes it very clear what is wanted in the report and looks like a comprehensive assessment, but without too much effort on the instructor's part. I also like the easy-to-use way that different aspects of the rubric are weighted.
Suggestion:
I might consider trying to simplify the rubric for the presentation scoring. While breaking down each scoring category into many points is helpful for guiding the students on what to expect, my concern is that it might be hard to assess all of those points while listening to the presentation. Perhaps save those points and give them to the students as guidance when they are preparing the presentation, but then simplify the rubric so that it is easier to use quickly.
Question:
One of the alignment objectives under Research Goal 1 and Student Goal 1 is "Demonstrate confidence in operating specialized glassware and equipment (such as Schenk line and drybox)." How can you assess that the student has confidence? What are you looking for?
14081:42067
Share
edittextuser=112413 post_id=42067 initial_post_id=0 thread_id=14081