The gas-phase study of doubly charged and ligated group III transition metal ions by Fourier transform mass spectrometry
Abstract
In addition to simple charge transfer, Y$\sp{2+}$ exhibits interesting reactivity with small alkanes. Mixtures of charge-transfer, hydride and methide transfer, dehydrogenation, and alkane loss products are observed. Y$\sp{2+}$ is unreactive with methane. The predominant product from reactions with ethane, propane, and butane is $\rm YC\sb2H\sb4\sp{2+}.$ A multicenter mechanism is proposed for these reactions. $\rm YC\sb2H\sb4\sp{2+}$ undergoes displacement reactions with propane and larger alkanes, indicating that electrostatic forces are mainly involved in the bonding in $\rm YC\sb2H\sb4\sp{2+}$ and the other dication products studied. In the reaction of YNH$\sp+$ with ethylene, $\rm YC\sb2H\sb3N\sp+$ is the predominant product. $\beta$-hydrogen transfer to the metal center is followed by elimination with a hydrogen from the remaining methylene group to complete the reaction. The $\rm YC\sb2H\sb3N\sp+$ is suggested to have an azametallacyclobut-3-ene structure. The subsequent reaction of $\rm YC\sb2H\sb3N\sp+$ with $\rm C\sb2H\sb4$ yields $\rm YC\sb4H\sb5N\sp+$ which is believed to be a metallabenzene with a CH replaced by NH. The dehydrogenation process is also facile in the reaction of YNH$\sp+$ with propene. The structure of the product, $\rm YC\sb3H\sb5N\sp+,$ is proposed to be either an azametallacyclobut-3-ene complex or a bent metallacyclopent-3-ene. ScH$\sp+$ and ScCH$\sb3\sp+$ are generated from the reactions of Sc$\sp{2+}$ with $\rm C\sb2H\sb6$ and $\rm C\sb3H\sb8,$ respectively. ScH$\sp+$ is unreactive with methane. $\rm ScC\sb2H\sb5\sp+$ is the only product observed in the reaction of ScH$\sp+$ with ethane, and its structure is proposed to be a (hydrido)(ethylene)scandium ion. Loss of H$\sb2$ or the combined loss of H$\sb2$ and CH$\sb4$ is observed as a major reaction channel for the reactions of the larger alkanes studied. A heterolytic reaction pathway proceeding via a four-center, four-electron transition state is proposed for these reactions. ScCH$\sb3\sp+$ reacts with alkanes to give the same product ions as were observed in the reactions of ScH$\sp+$ with alkanes, except that no reaction occurred for ScCH$\sb3\sp+$ with ethane. The same reaction mechanisms postulated for ScH$\sp+$ are expected for reactions of ScCH$\sb3\sp+$ with alkanes.
Degree
Ph.D.
Advisors
Freiser, Purdue University.
Subject Area
Analytical chemistry
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