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Applications of MS to Organometallic Chemistry

Parallelling Solution Phase and Ion-molecule Reactions in Gas-phase

! Theory

Short-lived intermediates of catalytic cycles can be trapped and identified and susequent ion-molecule reactions yields detailed information about single reaction steps of catalytic cycles.

Gas-phase reactions performed to corroborate species detected by MS to solution-phase species.

Me3N

Me3N

Cl

PCy2

H

Ru

Cl

PCy2

Ph

CID

1

ESI is used so that even weakly bound ligands will remain intact.

CID and thermalization withan inert gas in O1.

! Olefin Metathesis by Ruthenium Carbene Complexes

Increasing the collisional activation potential resulted in 1 predominantly going to 2 due to loss of the second phosphine ligand, loss of trimethylamine, and loss of HCl.

Me3N

Cl Cl

PCy2

Ru

H Ph

2

The species of interest is singled out by MS1.

The observed fragmentation pattern was consistent with the assumed structure of the ruthenium complex.

1-butene

reactionwith 1- butene in O2.

Reaction of 2 with 1-butene as reaction partner gave a new signal with the mass corresponding to the 3 via an olefin metathesis reaction.

Me3N

Cl Cl

PCy2

Ru

H3 CH2CH 3

Mass analysis by MS2.

Parallelling of gas and solution phase reactivity:

Dissociation of one phosphine ligand is a prerequiste for reactivity.

Kinetic preference for one propylidine complex (no other methylene complext detected).

Mohr,Lynn, & Grubbs: Organometallics 1996,15, 4317. Hinderling, Adlhart, & Chen: ACIE 1998, 37, 2685.

Diastereoselective Effects

MS Distinction of Stereoisomers in Arene Hydrogentation

! Exploring Metal-Catalyzed syn-Hydrogenations

H

[M]

H2

H

H2

H

H

H

H2

H

H

[M]

[M]

H

[M]

H

H

H

+/- [M]

H

H diastereomers

H

Can not be determined by 1H and 2H NMR because of overlapping signals

[M]

H

H

H2

H

[M]

H

H

H2

H

H

H

H

H

D

D

D

D

D

D

D

1

D

D

2

D

D

D

Schwaz, etal.: Organometallics 1995, 14, 4465.

! MS Stereoselective Effects by Isotopic Labeling

Diastereoselectivity of a hydrogentation is probed by using isotopic labelling and a gas-phase dehydrogenation reaction with bare Ti+.

Partial FTICR MS of triple hydrogenation of C6H6 shows that >99.5%all syn- hydrogenation of C6D6 and the triple dehydrogenation of occurs with >99.5 % diastereoselectivity

C6D

6

[M]

[ M ] = ( n 3 - C 3 H 5 ) C o [ O P ( O C H 3 ) 3 ] 3

D6

3

C 6 H 6 D

6

Ti+

10

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