Consecutive fragmentations of the cubane-like zinc cluster [CH3Zn(O-i-C3H7)]4 upon electron ionization

Abstract

The sequential dissociations of the tetranuclear zinc cluster-ion [(CH₃)₃Zn₄(O-i-C₃H₇)₄]⁺ obtained by dissociative electron ionization of neutral [(CH₃)Zn(O-i-C₃H₇)]₄ are investigated by tandem mass spectrometry. After initial loss of a neutral (CH₃)Zn(O-i-C₃H₇) unit to afford [(CH₃)₂Zn₃(O-i-C₃H₇)₃]⁺, hydrogen migration leads to the expulsion of neutral acetone concomitant with [(CH₃)₂Zn₃(O-i-C₃H₇)₂(H)]⁺ as ionic fragment. Unimolecular dissociation of the latter gives rise to [(CH₃)₂Zn₂(O-i-C₃H₇)]⁺ and neutral HZn(O-i-C₃H₇). As demonstrated by collisional ionization of the neutral product, in the fragmentation of the dinuclear cluster [(CH₃)₂Zn₂(O-i-C₃H₇)]⁺ neutral CH₃ZnH is formed, rather than the more stable fragments Zn + CH₄. From the resulting mononuclear species CH₃Zn(OC(CH₃)₂)⁺ acetone is eliminated to afford CH₃Zn⁺ as a quasi-terminal fragment ion.