GENERATION, ION-MOLECULE REACTIONS AND THERMOCHEMISTRY OF ATOMIC METAL ANIONS UTILIZING FOURIER TRANSFORM MASS SPECTROMETRY (HYDRIDE, SULFIDE, CARBONYLS, FTMS)

LARRY SALLANS, Purdue University

Abstract

The work presented in this thesis represents the first ion-molecule study of atomic metal anions. V('-), Cr('-), Fe('-), Co('-), Mo('-) and W('-) are generated by collision-induced dissociation, CID, of their respective anionic metal carbonyls using a Fourier transform mass spectrometer. Reactions of the atomic metal carbonyls resulted in dissociative charge transfer and the formation of dinuclear species such as Cr(,2)(CO)(,5)('-), V(,2)(CO)(,3)('-), V(,2)(CO)(,4)('-), Mo(,2)(CO)(,4)('-) and CrFe(CO)(,4)('-). The Cr(,2)(CO)(,5)('-) ion is extensively studied and experimental evidence that supports a weakly bound Cr-Cr(CO)(,5)('-) structure, is given. Cr(,2)(CO)(,5)('-) reacts with ketones and alkenes to produce adducts which are stabilized by decarbonylation. CID of these species results primarily in decarbonylation and dehydrogenation. The ketone adducts also produce OCr(,2)(CO)(,x)('-) (x = 2 - 4). Proton abstraction reactions are used to bracket the proton affinities of the metal anions (kcal/mol): V('-) (339.4 (+OR-) 3), Cr('-) (339.4 (+OR-) 3), Fe('-)(339.4 (+OR-) 3), Co('-)(340.5 (+OR-) 3), Mo('-)(342.4 (+OR-) 3). From these results and from the electron affinity of the corresponding metal atoms, the metal-hydrogen homolytic bond energies, D('o) M-H , are obtained (kcal/mol): V-H(37.9 (+OR-) 3), Cr-H(41.2 (+OR-) 3), Fe-H (29.6 (+OR-) 3), Co-H(42.2 (+OR-) 3), Mo-H(46.0 (+OR-) 3). Other derivable thermodynamic data include (DELTA)H(,f)('0)(MH) (V, Cr, Fe, Co, Mo), IP(MH) (Cr, Fe, Co), D('o) M-H('-) (Fe, Co) and D('o) M('-)-H (Fe, Co). Methyl cation affinity bracketing is also discussed. Reactions of the atomic metal anions with thiols, disulfides and sulfides predominantly involve the weak C-S bond. Processes such as direct cleavage, alkene loss and dehydrogenation, are commonly observed. Reactions of atomic metal anions with thiols result in the primary products MS('-), MSH('-) and HMSH('-) and the secondary products, MS(,2)H('-) and MS(,2)R('-). Structural implications by CID are discussed. From the reactions with thiols, H(,2)S and CS(,2), the following thermodynamic information is obtained (kcal/mol; M = Fe or Co): D('o) M('-)-S > 103.4; D('o) M('-)-SH = 83 (+OR-) 10; (DELTA)H(,f)('0)(FeS('-)) < 68; (DELTA)H(,f)('0)(CoS('-)) < 58; (DELTA)H(,f)('0)(FeSH('-)) = 47 (+OR-) 10, (DELTA)H(,f)('0)(CoSH('-)) = 37 (+OR-) 10; (DELTA)H(,f)('0)(FeSH(,2)('-)) < 72; (DELTA)H(,f)('0)(CoSH(,2)('-)) < 63. Reactions with the disulfides showed products arising from approx. 75% C-S and 25% S-S bond insertion. Only reactions involving larger acyclic and smaller cyclic sulfides were observed.

Degree

Ph.D.

Subject Area

Analytical chemistry

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