Insertion reactions of metal carbonyl anions with methyl formate in the gas phase as revealed by (13)C- and D-labeling.
School of Chemistry, University of New South Wales, Kensington, Australia Institute of Mass Spectrometry, University of Amsterdam, Nieuwe Achtergracht The gas-phase reactions of coordinatively unsaturated metal carbonyl anions (M(CO) n (-) , M=Cr, Mn, Fe, Co; n=0-3 and Co(CO)nNO(-), n=0-2) with unlabeled and D- and (13)C-labeled methyl formate have been studied with Fourier transform ion cyclotron resonance mass spectrometry. The reactions proceed in most instances by loss of one or more CO molecules from the collision complex. In the reactions of the dicarbonyl and tricarbonyl anions with H(13)COOCH3, part of the eliminated carbon monoxide molecules contain the label revealing the occurrence of initial insertion of the metal center into the bonds adjacent to the carbonyl function of the substrate with formation of five- or six-coordinate intermediates, respectively. In addition, the MnCCO) 3 (-) , Fe(CO) 2 (-) , and CoCCO) 2 (-) ions react by the loss of methanol and a [C,H2,O] neutral species. The D- and (13)C-labeling show that methanol is expelled in a reductive elimination from a five- or six-coordinate species, whereas the [C,H2,O] loss is a more complex process possibly involving the competing losses of formaldehyde and CO + H2. In the reaction of Fe(CO) 3 (-) with H 13 (13) COOCH3, a facile consecutive exchange of all three CO ligands of the reactant ion for (13)CO is observed. This novel reaction appears to involve initial insertion into the H(13)CO-OCH3-bond followed by facile hydrogen shifts from the formyl ligand to a CO Hgand prior to the loss of unlabeled methyl formate.
Institute of Mass Spectrometry, University of Amsterdam, Nieuwe Achtergracht 129, 1018 WS, Amsterdam, The Netherlands.
K J
KJ
van den Berg
S
S
Ingemann
N M
NM
Nibbering
I K
IK
Gregor