Alkyl and aryl dicationic derivatives of cyclic triphosphenium ions

Abstract

Direct alkylation of cyclic triphosphenium ions by triflates to give di-ium dications is only possible for small organic substituents on the attacking reagent. The dicationic products are not intrinsically unstable, however, and in many instances they may be synthesised by an alternative route, pioneered by Schmidpeter and co-workers. These species may be readily identified in solution by (31)P NMR spectroscopy. The crystal and molecular structures of five such derivatives have been ascertained for the first time by single crystal X-ray diffraction at 120 K. The results confirm that normal single P-P bond lengths are present in the dications, in contrast with the monocationic parent cyclic triphosphenium ions, where structural determinations have shown that the P-P bond lengths are intermediate between single and double bonds.

Phosphine complexes of lone pair bearing Lewis acceptors

“…58,59 The phosphine centre in [(PMe 3 )PMe 2 ] 1+ can be alkylated to give [P 2 Me 6 ] 2+ , 60 which is analogous to methylation of a triphosphenium cation (Scheme 6c). 61 Single and double coordination of transition metals at lone pairs of neutral P(I) centres has also been reported (Scheme 6d-f, Fig. 9a and 9b).…”

Phosphines and related C–P bonded compounds

“…377 The reactivity of the central cationic phosphorus atom in such systems towards alkylating agents has also been explored. 378 Interest has also continued in studies of the generation and reactivity of phosphinidene species (RP:), phosphorus analogues of carbenes. Streubel's group has reported the isolation of the first complexed phosphinidene precursor, the Li/halogen phosphinidenoid transition metal complex (176), a yellow solid that begins to decompose above 10 1C to give products derived from the liberated phosphinidene.…”

The relative stabilities of cyclic dicationic derivatives of diphosphanes with three (3P) or four (4P) linked phosphorus atoms

“…1 These compounds may also be prepared by direct alkylation of cyclic triphosphenium ions (CTIs) on the central (bare) phosphorus atom, at least for small R¢ groups (Scheme 2). 2, 3 In a recent paper, we described the synthesis by these two routes of several new 3P compounds, five of which were characterised by single-crystal Xray diffraction. Fig.…”

“…8 and 9 were prepared by direct methylation using methyl triflate of the corresponding cyclic triphosphenium ion (Scheme 2). 2, 3 For biphep and cybiphep derivatives only, the outer phosphorus atoms P B and P C are inequivalent, so the P A resonance appeared as a doublet of doublets (Table 1). In all instances, the 1 J PP values are appreciably smaller than those in the corresponding cyclic triphosphenium ions, with no substituent on P A . ]…”