Bis(imino)pyridine Iron Catalyzed Alkene Hydrogenation Report

This report summarizes a study on the functional group tolerance and substrate scope in bis(imino)pyridine iron catalyzed alkene hydrogenation. The research investigates the hydrogenation of allyl amines, ether-substituted olefins, and carbonyl-substituted alkenes using the catalyst (iPrPDI)Fe(N2)2. The study highlights the impact of steric protection of the nitrogen donor on turnover frequencies, the hydrogenation activity of carbonyl-substituted alkenes, and the tolerance of esters and ketones. Stoichiometric experiments were performed to probe the interaction of the iron substrate with amines and ketones. The report also touches upon the synthesis of bis(imino) pyridine iron amine and ketone complexes, including the use of NMR spectroscopy, Mössbauer spectroscopy, and X-ray diffraction to determine the molecular and electronic structure of the complexes. The findings demonstrate the catalyst's efficiency and sensitivity to different functional groups, offering insights into the optimization of alkene hydrogenation processes.

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Running Head: Bis(imino)pyridine Iron Catalyzed Alkene Hydrogenation
Summary of study in Functional Group Tolerance and Substrate Scope in
Bis(imino)pyridine Iron Catalyzed Alkene Hydrogenation
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Bis(imino)pyridine Iron Catalyzed Alkene Hydrogenation 2
Catalyzed olefin hydrogenation.
This article examines the functional group tolerance and scope of substrate for bis(imino)
pyridine iron, catalyzed olefin hydrogenation.
The organic transformation discussed is the hydrogenation of the Allyl amines with structure;
R2NCH2CH═CH2 (R = H, Me).
The catalyst involved in the hydrogenation process is of the structure (iPrPDI = 2,6-(2,6-iPr2-
C6H3N═CMe)2C5H3N, 1-(N2)2).
The findings of the study show that bis(imino)pyridine iron bis(dinitrogen) complex, 1-(N2)2
catalyzes the hydrogenation process of olefins when subjected to unprotected amines, a variety
of carbonyls as well as fluorinated hydrocarbons.
Turnover frequencies
It was observed that the turnover frequencies increased with steric protection of the nitrogen
donor.
ether-substituted olefins
The article also illustrates hydrogenation of ether-substituted olefins such as ethyl vinyl ether,
ethyl allyl ether, and allyl with turnover frequencies similar to the analogous α-olefins.
Carbonyl-substituted alkenes
It is illustrated that hydrogenation activity for the carbonyl-substituted alkenes is quite sensitive
to the position and type of the functional group. Similarly, esters like the dimethyl itaconate
and trans-methyl cinnamate are observed to effectively hydrogenate at 23 degrees Celsius.
Conversely, ketones like 5-hexen-2-one have a turnover of at least 65 degrees Celsius.
Conjugated α, β-unsaturated ketones
It is illustrated in the study that conjugated α, β-unsaturated ketones cause induction in the
process of iron compound decomposition because of a relatively low potential for one-electron
redox. Similarly, it is illustrated that α, β-unsaturated esters are easily tolerated by the iron
catalyst leading to higher efficiency of the hydrogenation turnover process.
A reasonable turnover heating for ketone, 5-hexen-2-one is illustrated to be 65 °C. Conversely, it
is illustrated that it was not possible to hydrogenate (+)-dihydrocarvone even within a high
temperature of (65 °C).
Stoichiometric experiments
Stoichiometric experiments conducted between 1-(N2)2 and the amines probed the interaction of
iron substrate and gauged the level of functional group coordination affinity in relation to the
alkene.

Bis(imino)pyridine Iron Catalyzed Alkene Hydrogenation 3
It is observed that adding 1 equiv of allylamine to 1-(N2)2 did not only produce dinitrogen gas
but yielded a brown solid structurally represented as 1-NH2CH2CHdCH2.
Similar procedure used propylamine and N-methylallylamine to isolate the analogous products,
1-NH2CH2CH2CH3 and 1-NH(Me)CH2CHdCH2 in that order.
An experiment involving N, N-dimethylallylamine and 4-methyl-1-pentene is reported not to
have shown change in the benzene-d6 1 H NMR spectra of 1-(N2)2.
Synthesis of bis(imino) pyridine iron amine and ketone complexes
Various bis(imino) pyridine iron amine and ketone complexes are synthesized. In this instance
NMR spectroscopy, Mössbauer spectroscopy and X-ray diffraction were used in probing the
molecular and electronic structure. Particularly, x-ray diffraction was utilized in determine the
solid-state structure of 1-OCPh2