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Large effect of a small substitution: competition of dehydration with charge retention and Coulomb explosion in gaseous [(bipyR)Au(μ-O)2Au(bipyR)]2+ dications

Tyo, Eric C. and Castleman, A. W., Jr and Schröder, Detlef and Milko, Petr and Roithová, Jana and Ortega, Jean-Michel and Cinellu, Maria Agostina and Cocco, Fabio and Minghetti, Giovanni (2009) Large effect of a small substitution: competition of dehydration with charge retention and Coulomb explosion in gaseous [(bipyR)Au(μ-O)2Au(bipyR)]2+ dications. Journal of the American Chemical Society, Vol. 131 (36), p. 13009-13019. eISSN 1520-5126. Article.

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DOI: 10.1021/ja902773b

Abstract

Dinuclear gold(III) clusters with a rhombic Au2O2 core and 2,2′-bipyridyl ligands substituted in the 6-position (bipyR) are examined by tandem mass spectrometry. Electrospray ionization of the hexafluorophosphate salts affords the complexes [(bipyR)Au(μ-O)2Au(bipyR)]2+ as free dications in the gas phase. The fragmentation behavior of the mass-selected dications is probed by means of collision-induced dissociation experiments which reveal an exceptionally pronounced effect of substitution. Thus, for the parent compound with R = H, i.e., [(bipy)Au(μ-O)2Au(bipy)]2+, fragmentation at the dicationic stage prevails to result in a loss of neutral H2O concomitant with an assumed rollover cyclometalation of the bipyridine ligands. In marked contrast, all complexes with alkyl substituents in the 6-position of the ligands (bipyR with R = CH3, CH(CH3)2, CH2C(CH3)3, and 2,6-C6H3(CH3)2) as well as the corresponding complex with 6,6′-dimethyl-2,2′-dipyridyl as a ligand exclusively undergo Coulomb explosion to produce two monocationic fragments. It is proposed that the additional steric strain introduced to the central Au2O2 core by the substituents on the bipyridine ligand, in conjunction with the presence of oxidizable C−H bonds in the substituents, crucially affects the subtle balance between dication dissociation under maintenance of the 2-fold charge and Coulomb explosion into two singly charged fragments.

Item Type:Article
ID Code:4252
Status:Published
Refereed:Yes
Uncontrolled Keywords:C-H bond, gold(III) oxo complexes, gas-phase reactivity, transition-metal oxo, gold alkene complexes, ray crystal-structure, quadrupole ion-trap, structural-characterization, dioxygen activation, platinum(II) derivatives
Subjects:Area 03 - Scienze chimiche > CHIM/03 Chimica generale e inorganica
Divisions:001 Università di Sassari > 01 Dipartimenti > Chimica
Publisher:American Chemical Society
eISSN:1520-5126
Deposited On:23 Jul 2010 12:07

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