IN PURSUIT OF A TRANS-CHELATING DIPHOSPHINE

LIGANDJacqueline 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 PearsallAssistant: Nicholas Chiappini

NJGSS 2014 Drew University – Team Project 3

Coordination Complexes

ASome Ligand

Some Central Atom/Ion

Be-

e-

Organometallic Complexes

•Useful as catalysts•Possess other unique properties

INTRODUCTION

MC

Ligands and Chelation

Halides AminesCarbon

ylsPhosphin

esDiphosphin

e

Diphosphines chelate. That is, they can form coordinate covalent bonds in a complex at

multiple sites.

INTRODUCTION

The Experimental Goal

Molybdenum Hexacarbonyl

(Mo(CO)6)

Mo(CO)4[(Ph2P)(CH2)n(PPh2)]

INTRODUCTION

Experimental Obstacles

CO

CO

CO

CO

CO

CO

Mo

CO

CO

CO

CO C

O

Mo

MonosubstitutionTrisubstitutionDisubstitution

PPh2 PPh2

Mo(CO)6 [(Ph2P) (CH2) n (PPh2) ]

CO

CO

CO

CO

CO

CO

Mo

PPh2 PPh2

PPh2

PPh2

CO

CO

CO

CO

CO

Mo

CO

CO

CO

CO

CO

CO

Mo

CO

CO

CO

CO

CO

CO

Mo

PPh2

PPh2

PPh2

PPh2

PPh2 PPh2

PPh2 PPh2

Molybdenum hexacarbonyl reacts with phosphenes in multiple ways

CO

CO

Mo

PPh2

PPh2

CIS TRANS

INTRODUCTION

Activated Precursor Complexes

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

CO

CO

CO

CO

CO

MoCO

How do we obtain a guaranteed trans

product?

pippip

pip

pippip

pipPPh

2

PPh2

PPh2

PPh2

INTRODUCTION

Varying Hydrocarbon Length

LIGANDS

Longer hydrocarbon length = greater freedom of the

diphosphine to chelate in a trans configuration

INTRODUCTION

1,4

1,5

1,6

1,8

1,12

Expectations

HypothesesAs 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.

INTRODUCTION

Procedure and Rationale

EXPERIMENTAL

CO

CO

CO

CO

Mo C

O

COpip

pip

PPh2

PPh2

PPh2

PPh2

CO

Day 1:Mo(CO)6 + 2 pip Mo(CO)4(pip)2 + 2

COHeat

Day 2:Mo(CO)4(pip)2 + [(Ph2P)(CH2)n(PPh2)] cis-Mo(CO)4 [(Ph2P)

(CH2)n(PPh2)] + 2 pipHeat

Day 3:cis-Mo(CO)4 [(Ph2P)(CH2)n(PPh2)] trans-

Mo(CO)4 [(Ph2P)(CH2)n(PPh2)]Heat

Collecting Data – IR

EXPERIMENTAL

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)6 Number of

Distinct Dipole Shifts:

1

Expected Peaks:

1

Mo(CO)4 (pip)2Number of

Distinct Dipole Shifts:

3

Expected Peaks:

3

cis- Mo(CO)4 [(Ph2P) (CH2)n(PPh2)]Number

of Distinct Dipole Shifts:

3

Expected Peaks:

3

trans- Mo(CO)4 [(Ph2P) (CH2)n(PPh2)]Number

of Distinct Dipole Shifts:

1

Expected Peaks:

1

pip

pip

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.

EXPERIMENTAL

cis-Mo(CO)4(PPh3)2

Mo(CO)4(PPh3)2 + Δ

IRN

M RControl Group, Ligand PPh3

RESULTS

cis-Mo(CO)4[(Ph2P)(CH2)12(PPh2)]

Mo(CO)4[(Ph2P)(CH2)12(PPh2)] + Δ

IRN

M R1,12 Group, Ligand (PPh2)2(CH2)12

RESULTS

cis-Mo(CO)4[(Ph2P)(CH2)8(PPh2)]

Mo(CO)4[(Ph2P)(CH2)8(PPh2)] + Δ

IRN

M R1,8 Group, Ligand (PPh2)2(CH2)8

RESULTS

cis-Mo(CO)4[(Ph2P)(CH2)4(PPh2)]

Mo(CO)4 [(Ph2P)(CH2)4(PPh2)] + Δ

IRN

M R1,4 Group, Ligand (PPh2)2(CH2)4

RESULTS

cis-Mo(CO)4[(Ph2P)(CH2)5(PPh2)]

Mo(CO)4[(Ph2P)(CH2)5(PPh2)] + Δ

IRN

M R1,5 Group, Ligand (PPh2)2(CH2)5

RESULTS

cis-Mo(CO)4[(Ph2P)(CH2)6(PPh2)]

Mo(CO)4[(Ph2P)(CH2)6(PPh2)] + Δ

IRN

M R1,6 Group, Ligand (PPh2)2(CH2)6

RESULTS

Discussion: Conclusions

ANALYSIS

Incre

asin

g e

ffica

cy o

f cis-tran

s co

nversio

n

# of Carbons in

Ligand

Ligand (Chemical)

Ligand (Structural)

cis-trans Conversion Notes

4 [(Ph2P)(CH2)4(PPh2)]

No Conversion

5 [(Ph2P)(CH2)4(PPh2)]

No Conversion

6 [(Ph2P)(CH2)4(PPh2)]

Some Conversion

8 [(Ph2P)(CH2)4(PPh2)]

Mostly Conversion

12 [(Ph2P)(CH2)4(PPh2)]

Mostly 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.

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

Dr. Mary-Ann Pearsall Nicholas Chiappini