Furthermore, preliminary studies suggest that the cationic phosphaalkene + may be employed to access rare examples of η 2–P═C π-complexes with Pd 0 and Pt 0 when treated with and for which analogous complexes of neutral phosphaalkenes are scarce. To test this hypothesis, treatment of + with phosphaalkenes, that are isolobal to thioketones, permits the isolation of diphosphirane salts 11a,b. Theoretical calculations suggest that three-membered cyclic thiophosphiranes are crucial intermediates of this reaction.
They act as + transfer reagents in phospha-Wittig-type reactions, when converted with various thiocarbonyls, giving unprecedented cationic phosphaalkenes + ( 5a-f) or phosphanides + ( 6a-d). Cationic imidazoliumyl(phosphonio)-phosphanides + ( 1a–e +, L C = 4,5-dimethyl-1,3-diisopropylimidazolium-2-yl R = alkyl, aryl) are obtained via the nucleophilic fragmentation of tetracationic tetraphosphetane 4 ( 2 4) with tertiary phosphanes.
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