Comparative study of mono- and dinuclear complexes of late 3d-metal chlorides with N,N-dimethylformamide in the gas phase

Mono- and binuclear complexes of N,N-dimethylformamide (DMF) with chlorides of the divalent, late 3d metals M = Co, Ni, Cu, and Zn are investigated by means of electrospray ionization (ESI). Specifically, ESI leads to monocations of the type (DMF)(n)MCl](+) and (DMF)(n)M(2)Cl(3)](+), of which the species with n = 2 and 3 were selected for in-depth studies. The latter include collision-induced dissociation experiments, gas-phase infrared spectroscopy, and calculations using density functional theory. The mononuclear complexes (DMF)(n)MCl](+) almost exclusively lose neutral DMF upon collisional activation with the notable exception of the copper complex, for which also a reduction from Cu(II) to Cu(I) concomitant with the release of atomic chlorine is observed. For the dinuclear clusters, there exists a competition between loss of a DMF ligand and cluster degradation via loss of neutral MCl(2) with decreasing cluster stability from cobalt to zinc. For the specific case of (DMF)(n)ZnCl](+) and (DMF)(n)Zn(2)Cl(3)](+), ion-mobility mass spectrometry indicates the existence of two isomeric cluster ions in the case of (DMF)(2)Zn(2)Cl(3)](+) which corroborates parallel theoretical predictions.