Organometallic compounds. VI . Electron impact fragmentation of some mixed and symmetrical tetraalkyltins

Mechanism and Unusual Fragmentation Selectivities of Aryltrialkylstannane Cation Radicals

Aryltrialkylstannane cation radicals were generated and characterized by nanosecond transient absorption spectroscopy. Kinetics show the fragmentations of the stannane cation radicals occur by a bimolecular, nucleophile-assisted mechanism (S(N)2). Consistent with this hypothesis, steric effects on both the nucleophile and the stannane cation radicals were observed. Steady-state, preparative photooxidation experiments show that aryltrimethylstannane cation radicals have an unusual preference for loss of aryl radicals over methyl radicals and that the selectivity for aryl vs methyl radical loss is dependent on the identity of the nucleophile. The preference for loss of aryl radicals is rationalized by a hypothesis based on Bent's rules.

Band composition analysis: a new procedure for deconvolution of the mass spectra of organometallic compounds

A new chemometric procedure called band composition analysis (BCA) designed for the deconvolution of mass spectra of organometallics is proposed. BCA generates theoretical bands T(i), then combines them to obtain a model band M, which is finally compared with the experimental band E. All of these steps are realized with computer assistance. This modeling yields four parameters characterizing the experimental band: theoretical and model variances s(2) (theor) and s(2) (model), a fit factor alpha and a contribution x(i) from the theoretical band. If s(2) (theor) > 20 the band is deemed complex and needs modeling. The values alpha > 90 indicate that there is good agreement between the experimental and model bands. BCA is particularly effective for the modeling of complex isotopic bands often present in organometallics. Two illustrations of BCA for tetrabutyltin, C(16)H(36)Sn, and 1,1',2,2',3,3'-hexachloroferrocene, C(10)H(4)Cl(6)Fe, are shown.