MS MS MS Mass Spectrometry Organometallics

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.click here Recommendations We recommend you confer with your friendly local mass spectrometrist before preparing any organometallic or inorganic samples for mass spectrometry.

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. (M+H) + ; (M+Na) +, (M+matriz) +, 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. [M+nH] n+, [M+Na] +, etc.

Isotope patterns Aluminium Bromide: AlBr + 27 Al : 100% 79 Br : 51% 81 Br : 49%

Isotope patterns 63 Cu: 69.1% 65 Cu: 30.9% 35 Cl: 75.5% 37 Cl: 24.5% 63 Cu 35 Cl 63 Cu 37 Cl 65 Cu 35 Cl 65 Cu 37 Cl Abundance of first isotope peak M Abundance of first isotope peak M:.691 x.755 =.521 For next isotope peakM+2: For next isotope peak: M+2:.691 x.245 = x.755 =.233 }.403 For next isotope peakM+4: For next isotope peak: M+4:.309 x.245 =.076

Poly-isotopic metals Metal isotope pattern are distorted by 13 C and 2 H

Poly-isotopic metals When more than one metal is present: pattern is affected in a predictable way

Ru1 Ru2 (bpy)(tpy)RuN 2 ArN 2 Ru(bpy)(tpy)?

Reacciones ion-molécula Se producen ocasionalmente, dando lugar a iones de MAYOR masa que el ion molecular. Cr(CO) 6 + Cr(CO) 10 Cr(CO) Cr(CO) 6 --> Cr(CO) CO

Fragmentation 1.The charge is likely to remain on Metal-containing fragment MLnMLnMLnMLn M L n-1 + L M L n L L + ML n-1 L + + M L n-1 Less likely 2.Rearrangement involving hydrogen migration are frequent (M => Si, Ge, Sn, Pb…)

Fragmentation 3.Migration of Halogens is very common M (C 6 F 5 ) 3 + (C 6 F 5 ) 2 Sn F + (C 6 F 5 ) 2 Sn F + + C 6 F 4 M => Si, Ge, Sn, Pb 4.Migration of Alkyl to metal is also common Transfer of R is influence by electronegativity of the R group

process Rearrangement process “McLafferty” type of rearrangement involving metal instead of H This rearrangement depends on readiness of metal to become pentacoordinate (using it’s d-orbitals)

Metal Carbonyls (Co)

Metal Carbonyls (Fe)

Carbonyl halide compounds Terminal Bridging

Terminal Bridging Loss of CO and X occur with equal ease Loss of CO occur stepwise with retention of M 2 X 2 than further X loss can occur

Cs 2 IrCl 5 CO (ESI-MS(-)) IrCl 4 CO - IrCl 5 CO 2- IrCl 4 -

MSMS 199 ( IrCl 5 CO 2- ) IrCl 4 - IrCl 4 CO -

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.

[Ru(CpPh 5 )] 2 BrO+

[(CpPh 5 )Ru(CO) 2 ] 2 (PhCH 2 O) +