Conformational Switching through the One‐Electron Reduction of an Acridinium‐based, γ‐Cationic Phosphine Gold Complex

Abstract

Our efforts in the chemistry of gold complexes featuring ambiphilic phosphine‐carbenium L/Z‐type ligand have led us to consider the reduction of the carbenium moiety as a means to modulate the gold–carbenium interaction present in these complexes. Here, it was shown that the one‐electron reduction of [(o‐Ph2P(C6H4)Acr)AuCl]+ (Acr=9‐N‐methylacridinium) produces a neutral stable radical, the structure of which showed a marked increase in the Au–Acr distance. Related structural changes were observed for the phosphine oxide analogue [(o‐Ph2P(O)(C6H4)Acr]+, the reduction of which interfered with the P=O→carbenium interaction. These structural effects, driven by a reduction‐induced change in the electronic and electrostatic characteristics of the compounds, showed that the charge and accepting properties of the carbenium unit can be modulated. These results highlight the redox‐noninnocence of carbenium Z‐type ligand, a feature that can be exploited to induce specific conformational changes.

Placing gold on a π+-surface: ligand design and impact on reactivity

“…The same procedure can be used to generate the triate salt of [3 acr ] + . These salts have been analysed by 13 C NMR spectroscopy which shows a signal at 176.3 ppm for [3 xant ]OTf and 161.2 ppm for [3 acr ]OTf corresponding to the resonance of the carbenium C carb centre of the xanthylium and acridinium unit, respectively. 8 The phosphorus chemical shis of both complexes (30.2 ppm for [3 xant ]OTf and 30.7 ppm for [3 acr ]OTf) are consistent with the presence of a triarylphosphine-AuCl motif.…”

Green‐Light‐Driven Reductive Elimination of Chlorine from a Carbene‐Xanthylium Gold(III) Complex

“…We have recently introduced a family of gold complexes such as [ A ] + and [ B ] + featuring acridinium‐ or xanthylium‐based ambiphilic ligands (Figure 1). [6] Analyses of these complexes show that the gold‐bound chloride engages with the π + ‐surface [7] of the heterocyclic carbenium unit [6d] . The Au−Cl−π + interaction is largely electrostatic, leaving the electron‐deficient features of the carbenium unit unperturbed.…”

“…The Au−Cl−π + interaction is largely electrostatic, leaving the electron‐deficient features of the carbenium unit unperturbed. For example, the acridinium unit in [ A ] + can be easily reduced by one electron to afford the corresponding radical A ⋅ [6d] . The presence of this uncompromised carbenium unit allows for a connection to be made with the chemistry of photoredox catalysts such as [ C ] + , a molecule introduced by Fukuzimi two decades ago [8] .…”

“…Because of the rigidity of the backbone, the gold and chlorine atoms sit directly above the mean plane of the xanthylium unit (mpln xant ), leading to Au−mpln xant normal distances of 3.238(6) Å (molecule I) and 3.257(5) Å (molecule II) and Cl−mpln xant distances of 3.775(7) Å (molecule I) and 4.105(5) Å (molecule I). These short distances suggest that the carbene‐bound gold chloride unit may be interacting with the π + ‐surface of the xanthylium unit via Coulombic interactions [6b, d] . The asymmetric unit of 6 also possesses two molecules that resemble those in [ 3 ] + [12] .…”

Tri(N-carbazolyl)phosphine Gold(I) Complexes: Structural and Catalytic Activity Studies

“…Phosphine ligand-stabilized gold­(I) complexes represent an important class of gold complexes that have found wide applications in the field of catalysis and medicinal chemistry . The design, synthesis, and functional development of gold complexes bearing novel phosphine ligands constitute an active area of research, and those gold complexes exhibiting various interesting functionalities are continuously being developed . In contrast to the trialkyl/aryl phosphine and trialkyl/aryl phosphite ligands, phosphorous triamides have rarely been exploited as gold­(I) ligands.…”