MS Mass Spectrometry

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MS Mass Spectrometry

• Organometallics

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Centro de espectrometría de masa (Harvard)

• General Information
• The word that best describes the mass
  spectrometry of inorganic and Organometallic
  molecules is "difficult".
• Many species are intractable to mass spectrometry
  for one of a number of reasons.     To see our
  recommendations for Organometallic, click here.

Recommendations We recommend you confer with
your friendly local mass spectrometrist before
preparing any organometallic or inorganic samples
for mass spectrometry.
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Métodos de Ionización (los más usuales)

• EI (Impacto Electrónico) se volatiliza la
  muestra y se ioniza con un haz de electrones. M.
  y fragmentos
• FAB (Fast Atom Bombardment) se coloca la muestra
  en una matriz líquida (un alcohol) y se impacta
  con un haz de átomos de Xe. (MH) (MNa),
  (Mmatriz), fragmentos, etc
• MALDI (Matrix-Assisted Laser Desorption/Ionization
  ) se coloca la muestra en una matriz sobre un
  metal y se impacta con un laser. Muy usado para
  péptidos y proteínas.
• ESI (ElectroSpray Ionization) se disuelve la
  muestra, se pasa por un capilar a 5 kV, que la
  dispersa en microgotas. MnHn, MNa, etc.

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Isotope patterns
Aluminium Bromide
AlBr 27Al 100 79Br 51 81Br 49
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Isotope patterns
63Cu35Cl
63Cu 69.1
35Cl 75.5 37Cl 24.5
63Cu37Cl
65Cu35Cl
65Cu 30.9
65Cu37Cl
Abundance of first isotope peak M .691 x .755
.521
For next isotope peak M2 .691 x .245 .169

.403
.309 x .755 .233
For next isotope peak M4 .309 x .245 .076
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Poly-isotopic metals
Metal isotope pattern are distorted by 13C and 2H
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Poly-isotopic metals
When more than one metal is present pattern is
affected in a predictable way
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Ru1
(bpy)(tpy)RuN2ArN2Ru(bpy)(tpy)?
Ru2
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Reacciones ion-molécula
Se producen ocasionalmente, dando lugar a iones
de MAYOR masa que el ion molecular.
Cr(CO)6 Cr(CO)6 --gt Cr(CO)10 2 CO
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Fragmentation

• The charge is likely to remain on
  Metal-containing fragment

M Ln-1 L
MLn
L M Ln-1
Less likely

• Rearrangement involving hydrogen migration are
  frequent
  (M gt Si, Ge, Sn, Pb)

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Fragmentation

• Migration of Halogens is very common

M (C6F5)3
(C6F5)2 Sn F C6F4
M gt Si, Ge, Sn, Pb

• Migration of Alkyl to metal is also common

Transfer of R is influence by electronegativity
of the R group
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Rearrangement process
McLafferty type of rearrangement involving
metal instead of H
This rearrangement depends on readiness of metal
to become pentacoordinate (using its d-orbitals)
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Metal Carbonyls (Co)
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Metal Carbonyls (Fe)
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Metal Carbonyls (Fe)
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Carbonyl halide compounds
Terminal
Bridging
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Carbonyl halide compounds
Terminal
Loss of CO and X occur with equal ease
Bridging
Loss of CO occur stepwise with retention of M2X2
than further X loss can occur
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Cs2IrCl5CO (ESI-MS(-))
IrCl4CO-
IrCl4-
IrCl5CO2-
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MSMS 199 (IrCl5CO2-)
IrCl4CO-
IrCl4-
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FTMS

• Fourier transform mass spectrometry, is a type of
  mass spectrometer for determining the m/z of ions
  based on the cyclotron frequency of the ions in a
  fixed magnetic field.
• The ions are trapped in a magnetic field with
  electric trapping plates where they are excited
  to a larger cyclotron radius by an oscillating
  electric field perpendicular to the magnetic
  field. The excitation also results in the ions
  moving in phase (in a packet). The signal is
  detected as an image current on a pair of plates
  which the packet of ions passes close to as they
  cyclotron. The resulting signal is called a free
  induction decay (FID), transient or interferogram
  that consists of a superposition of sine waves.
  The useful signal is extracted from this data by
  performing a Fourier transform to give a mass
  spectrum.

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Ru(CpPh5)2BrO
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(CpPh5)Ru(CO)22(PhCH2O)