P-Protected Diphosphadibenzo[a,e]pentalenes and Their Mono- and Dicationic P-Bridged Ladder Stilbenes

Abstract

The previously elusive diphosphadibenzo­[a,e]­pentalene core skeleton was assembled via a surprisingly straightforward cyclization pathway starting from R2P-substituted 2,2′-diphosphinotolanes (R = Ph, i Pr). The resulting P-protected diylidic compounds 4 (R = Ph, i Pr) were converted to the corresponding P-bridged ladder stilbenes via two consecutive oxidation steps: upon selective one-electron oxidation, the persistent radical monocations 5 (R = Ph, i Pr) were obtained and further oxidized to afford the respective fluorescent and air-stable dications 6 (R = Ph, i Pr).

A 2,2′-diphosphinotolane as a versatile precursor for the synthesis of P-ylidic mesoionic carbenes via reversible C–P bond formation

“…As expected (vide supra), p-backbonding IBO interactions were only detected for complexes 6-11, but not for the d 0 -and d 10 -congured derivatives ([3] + , 4, 5 and 12). To gain further insights into the electronic structures of the latter four complexes, energy decomposition analysis (EDA-NOCV) was used to fragment each complex into a closed-shell ligand part and a closed-shell metal-containing part.…”

“…For the formation of cyclo-1 in the absence of a metal complex, solution of 1 need to be kept at 60 °C for several days. 10 Therefore, it is assumed that pyridine- d 5 coordinates to the metal centres in 3 and 12 , which induces the second cyclisation event, either with the CArY-MIC still within the coordination sphere of the metal or via displacement and liberation of the free carbene. The free carbene is then expected to either rapidly cyclise to cyclo-1 or to ring-open to 1 .…”

“… 9 We have also shown that 1 is prone to a twofold cyclisation to selectively afford the diylide cyclo-1 (see Scheme 2 ). 10 In view of these findings, it seemed possible that the reaction between 1 and a metal template with two cis -positioned open coordination sites may afford the desired κ 2 -P,C-chelating CArY-MIC complexes via attack of only one phosphine at the central alkyne unit. 11 As reported herein, CArY-MIC s may indeed be trapped this way.…”

Cationic Organophosphorus Chromophores: A Diamond in the Rough among Ionic Dyes

“…The symmetrical dicationic stilbenes 40 a , b (Figure 13) are brightly fluorescent in both solution and solid state [69] . Remarkably, chloride 40 b gives the quantum yield of 0.74 in water ( λ em =518 nm) with significant Stokes shift of 5780 cm −1 that makes this motif an attractive paradigm for bioimaging purposes.…”

Straightforward access to multifunctional pi-conjugated P-heterocycles

“…1). [12] [13] In these systems also, the bonding topology results from a combination of resonant forms. Although these recent results highlighted the promising optical and redox properties of these "ylidic" P-heterocycles in the context molecular electronics and photonics, efficient synthetic methods to prepare them remain limited.…”