Phosphonium ions of 2,4,6,8-tetra-tert-butyl-1,3,5,7-tetraphosphacubane and 1,2,5,6-tetraphosphatricyclo[4.2.0.02,5]-octa-3,7-diene in the gas phase: host–guest complexes, phosphonium ion decomposition pathways and interaction with onium ions (and carbocations). A field desorption (FD), fast atom bombardment (FAB) and tandem mass spectrometry (CAD–MS/MS) study

Abstract

We report a mass spectrometric study (FDMS, FABMS) of a series of phosphonium triflate salts derived from 2,4,6,8-tetra-tert-butyl-1,3,5,7-tetraphosphacubane 1 and 1,2,5,6-tetraphosphatricyclo[4.2.0.0^2,5]octa-3,7-diene 2, namely 3⁺(OTf)^–, 4⁺(OTf)^–, 5⁺(OTf)^–, 6²⁺(OTf·SbCl₆)^2–, 7²⁺(OTf·SbCl₆)^2– and 8⁺(OTf^–).

Except for the dications, the intact phosphonium ions were observed in all cases. The host–guest (H–G) chemistry of 3⁺ and some of its fragment ions with dicyclohexano-24-crown-8 have been probed. Low energy collisional decomposition of 3⁺ gives m/z 115 and 169 as prominent products for which structures 12⁺ and 11⁺ have been suggested in analogy with the recently discovered solution chemistries of phosphaalkynes and phosphirenes. The decomposition pathways of the studied phosphonium cations have been compared and discussed.