Metastable ion study of substituted cyclopentadienylmanganese cations in the gas phase

Abstract

The behavior of some substituted cyclopentadienylmanganese ions has been studied by tandem mass spectrometry. This metastable ion study showed that only C5H5Mn(+) and (C5H4CN)Mn(+) ions retain their nido-cluster structure (1), which is characterized by a simple metal-ligand bond cleavage. Other substituted ions, RXC5H4Mn(+), rearrange to a different extent, depending on the nature of the substituent. The first rearrangement step is R radical migration to the central metal atom, leading to RMnC5H4X(+)-type ions (2). These ions decompose by elimination of X (for X=CO) or with formation of RMnX(+), but further rearrangements can also occur. These are the reverse migration of R from the metal atom to the π-ligand (for R=H, Ph) and cyclopentadienyl ring expansion (for X=CH2). Collisional activation mass spectra contained an Mn(+) ion peak, which can indicate the existence of stable type 1 structures for most cyclopentadienylmanganese ions. Carboxyl and hydroxymethyl derivatives exist, presumably as ions of type 2. The neutralization-reionization mass spectra of RXC5H4Mn(+) ions are also discussed.

Neutralization‐reionization mass spectrometry applied to organometallic and coordination chemistry

“…In addition to a recovery signal, the NR mass spectrum of MnOH' displayed Mn+ and MnO' ion peaks (31). No MnH' ions were found, ruling out any significant isomerization of the cation or neutral MnOH to a structure with a metal-hydrogen bond.…”

“…The NR mass spectrum of MnC,Hl has been reported (31). This ion originated from Mn+C,H,COC,H, via the well-known migration of the P-substituent in the n--cyclopentadienyl ligand to the central metal atom (46,50).…”

“…Results of this study, and in particular the Recovery signals were observed for C,H,Rh+ (20) and C,H,Mn+ (31) ions, indicating the stability of their neutral counterparts, but neither the full NR mass spectra of these species nor any detailed discussion of results was reported. A series of substituted cyclopentadienyl-manganese ions of the formula Mn'C,H,XR was probed by NRMS (31) to study any substituent effect on the Mn'C,H,XR + RMn+C,H,X isomerization. The observation of a ligand ion for XR=CN was indicative of an intact Mn+C,H,XR structure, whereas C,H,X' ion formation corresponded to the isomer.…”