IN PURSUIT OF A TRANS-CHELATING DIPHOSPHINE LIGAND Jacqueline Dragon; Samuel Flanzman; Johann Frias; Michael Gao; JinOh Jeong; Angela Jin; Meeki Lad; Kevin Lin; Yuzki Oey; Jessica Teipel; Mathini Vaikunthan; Evan Zou Advisor: Dr. Mary-Ann Pearsall Assistant: Nicholas Chiappini NJGSS 2014 Drew University – Team Project 3

Coordination Complexes INTRODUCTION Coordination Complexes B e- C M A Some Ligand Organometallic Complexes Useful as catalysts Possess other unique properties Some Central Atom/Ion

Ligands and Chelation Halides Amines Diphosphine Carbonyls Phosphines INTRODUCTION Ligands and Chelation Halides Amines Diphosphine Carbonyls Phosphines Diphosphines chelate. That is, they can form coordinate covalent bonds in a complex at multiple sites.

The Experimental Goal INTRODUCTION Molybdenum Hexacarbonyl (Mo(CO)6) Mo(CO)4[(Ph2P)(CH2)n(PPh2)]

Experimental Obstacles INTRODUCTION Experimental Obstacles Molybdenum hexacarbonyl reacts with phosphenes in multiple ways Monosubstitution Disubstitution Trisubstitution CO PPh2 PPh2 CO CO Mo PPh2 CO CO Mo PPh2 CO Mo CO Mo CO Mo CO CO CO CO Mo Mo PPh2 CO CO CO PPh2 CO CO PPh2 CO PPh2 CO CO CO Mo(CO)6 [(Ph2P) (CH2) n (PPh2) ] CIS TRANS

Activated Precursor Complexes INTRODUCTION Activated Precursor Complexes PPh2 CO How do we obtain a guaranteed trans product? CO CO Use weak ligand (piperidine) Resulting activated precursor complex always involves disubstitution and occurs in the cis form Replace piperidine with diphosphine Heat to convert to trans Mo CO PPh2 CO CO pip pip pip pip pip pip

Varying Hydrocarbon Length INTRODUCTION LIGANDS Varying Hydrocarbon Length 1,4 1,5 1,6 1,8 1,12 Longer hydrocarbon length = greater freedom of the diphosphine to chelate in a trans configuration

Hypotheses Expectations INTRODUCTION Expectations Hypotheses As the length of the hydrocarbon chain increases, the trans isomer will become more favorable. Past a certain number of carbons, the hydrocarbon chain will be so long that it will form unintended alternate bonds.

Procedure and Rationale EXPERIMENTAL Procedure and Rationale Day 2: Mo(CO)4(pip)2 + [(Ph2P)(CH2)n(PPh2)] cis-Mo(CO)4 [(Ph2P)(CH2)n(PPh2)] + 2 pip Heat Day 3: cis-Mo(CO)4 [(Ph2P)(CH2)n(PPh2)] trans-Mo(CO)4 [(Ph2P)(CH2)n(PPh2)] Heat Day 1: Mo(CO)6 + 2 pip Mo(CO)4(pip)2 + 2 CO Heat CO Mo PPh2 PPh2 CO pip CO pip

Mo(CO)4 (pip)2 Mo(CO)6 Collecting Data – IR EXPERIMENTAL Collecting Data – IR Infrared Spectroscopy is a method of identifying chemical compounds by their characteristic dipole shifts and consequent % transmittance readings. This process was used at each experimental setup to confirm the presence of the desired compounds. Mo(CO)4 (pip)2 Mo(CO)6 cis- Mo(CO)4 [(Ph2P) (CH2)n(PPh2)] trans- Mo(CO)4 [(Ph2P) (CH2)n(PPh2)] pip Number of Distinct Dipole Shifts: 1 Expected Peaks: Number of Distinct Dipole Shifts: 3 Expected Peaks: Number of Distinct Dipole Shifts: 1 Expected Peaks: Number of Distinct Dipole Shifts: 3 Expected Peaks:

Collecting Data – Nuclear Magnetic Resonance Spectroscopy EXPERIMENTAL Collecting Data – Nuclear Magnetic Resonance Spectroscopy NMR is a method of spectroscopy that measures the alignment of phosphorus nuclei with a strong magnetic field, and in doing so, yields a graph that describes those atoms’ chemical environment.

Control Group, Ligand PPh3 RESULTS Control Group, Ligand PPh3 cis-Mo(CO)4(PPh3)2 Mo(CO)4(PPh3)2 + Δ IR NMR

1,12 Group, Ligand (PPh2)2(CH2)12 RESULTS 1,12 Group, Ligand (PPh2)2(CH2)12 cis-Mo(CO)4[(Ph2P)(CH2)12(PPh2)] Mo(CO)4[(Ph2P)(CH2)12(PPh2)] + Δ IR NMR

1,8 Group, Ligand (PPh2)2(CH2)8 RESULTS 1,8 Group, Ligand (PPh2)2(CH2)8 cis-Mo(CO)4[(Ph2P)(CH2)8(PPh2)] Mo(CO)4[(Ph2P)(CH2)8(PPh2)] + Δ IR NMR

1,4 Group, Ligand (PPh2)2(CH2)4 RESULTS 1,4 Group, Ligand (PPh2)2(CH2)4 cis-Mo(CO)4[(Ph2P)(CH2)4(PPh2)] Mo(CO)4 [(Ph2P)(CH2)4(PPh2)] + Δ IR NMR

1,5 Group, Ligand (PPh2)2(CH2)5 RESULTS 1,5 Group, Ligand (PPh2)2(CH2)5 cis-Mo(CO)4[(Ph2P)(CH2)5(PPh2)] Mo(CO)4[(Ph2P)(CH2)5(PPh2)] + Δ IR NMR

1,6 Group, Ligand (PPh2)2(CH2)6 RESULTS 1,6 Group, Ligand (PPh2)2(CH2)6 cis-Mo(CO)4[(Ph2P)(CH2)6(PPh2)] Mo(CO)4[(Ph2P)(CH2)6(PPh2)] + Δ IR NMR

Discussion: Conclusions ANALYSIS Discussion: Conclusions # of Carbons in Ligand Ligand (Chemical) Ligand (Structural) cis-trans Conversion Notes 4 [(Ph2P)(CH2)4(PPh2)] No Conversion 5 6 Some Conversion 8 Mostly Conversion 12 Increasing efficacy of cis-trans conversion

Ancillary Points Hypothesis was based solely on ball-and-stick models and was proven correct Knowledge of the spatial geometry can help predict the complex’s properties as well as those of similar complexes. Applications of trans-chelating diphosphine ligands in catalysis can now be explored.

Dr. Mary-Ann Pearsall Nicholas Chiappini Acknowledgments Independent College Fund of NJ/Johnson & Johnson AT&T Actavis Pharmaceuticals Celgene Novartis Bayer Healthcare Laura (NJGSS ’86) and John Overdeck NJGSS Alumnae and Parents of Alumnae Board of Overseers, New Jersey Governor’s Schools State of New Jersey Drew University