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. 2022 Oct 12;28(57):e202201856.
doi: 10.1002/chem.202201856. Epub 2022 Sep 1.

Heterobimetallic Gold/Ruthenium Complexes Synthesized via Post-functionalization and Applied in Dual Photoredox Gold Catalysis

Lea Bayer  1 , Bernhard S Birenheide  1 , Felix Krämer  1 , Sergei Lebedkin  2 , Frank Breher  1
Affiliations

Heterobimetallic Gold/Ruthenium Complexes Synthesized via Post-functionalization and Applied in Dual Photoredox Gold Catalysis

Lea Bayer et al. Chemistry. .

Abstract

The synthesis of heterobimetallic AuI /RuII complexes of the general formula syn- and anti-[{AuCl}(L1∩L2){Ru(bpy)2 }][PF6 ]2 is reported. The ditopic bridging ligand L1∩L2 refers to a P,N hybrid ligand composed of phosphine and bipyridine substructures, which was obtained via a post-functionalization strategy based on Diels-Alder reaction between a phosphole and a maleimide moiety. It was found that the stereochemistry at the phosphorus atom of the resulting 7-phosphanorbornene backbone can be controlled by executing the metal coordination and the cycloaddition reaction in a different order. All precursors, as well as the mono- and multimetallic complexes, were isolated and fully characterized by various spectroscopic methods such as NMR, IR, and UV-vis spectroscopy as well as cyclic voltammetry. Photophysical measurements show efficient phosphorescence for the investigated monometallic complex anti-[(L1∩L2){Ru(bpy)2 }][PF6 ]2 and the bimetallic analogue syn-[{AuCl}(L1∩L2){Ru(bpy)2 }][PF6 ]2 , thus indicating a small influence of the {AuCl} fragment on the photoluminescence properties. The heterobimetallic AuI /RuII complexes syn- and anti-[{AuCl}(L1∩L2){Ru(bpy)2 }][PF6 ]2 are both active catalysts in the P-arylation of aryldiazonium salts promoted by visible light with H-phosphonate affording arylphosphonates in yields of up to 91 %. Both dinuclear complexes outperform their monometallic counterparts.

Keywords: bimetallic complexes; cooperative effects; metalloligands; photoredox catalysts; post-functionalization.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Tethering transition metal catalyst and photoredox catalyst by post‐functionalization.
Scheme 1
Scheme 1
Synthesis of L2. bpy=4‐(2,2‘‐bipyridyl).
Scheme 2
Scheme 2
Synthesis of syn‐[{AuCl}(L1∩L2)] (2).
Scheme 3
Scheme 3
Synthesis of syn‐[{AuCl}(L1∩L2){Ru(bpy)2}][PF6]2 (3).
Figure 2
Figure 2
Molecular structure of syn‐[{AuCl}(L1∩L2){Ru(bpy)2}][PF6]2 (3). Hydrogen atoms, solvent molecules and counter ions have been omitted for clarity. Selected bond lengths [pm], angles [°] and distances [pm]: P1−Au1 221.53(18), Au1−Cl1 228.07(18), øRu1−N(bpy) 205.7(5); P1−Au1−Cl1 173.94(7), C1−N1−C20−C22 35.94; Au1⋅⋅⋅Ru1 1082.6 pm.
Scheme 4
Scheme 4
Synthesis of [(L2){Ru(bpy)2}][PF6]2 (4).
Figure 3
Figure 3
Calculated (BP86/SVP/D3BJ) minimum‐energy structures of the syn‐endo, syn‐exo, anti‐endo and anti‐exo isomers, their relative energies towards the syn‐endo isomer, and the calculated (TPSS/TZVP) 31P NMR chemical shifts.
Scheme 5
Scheme 5
Synthesis of anti‐[(L1∩L2){Ru(bpy)2}][PF6]2 (5).
Scheme 6
Scheme 6
Synthesis of anti‐[{AuCl}(L1∩L2){Ru(bpy)2}][PF6]2 (6).
Figure 4
Figure 4
Cyclic voltammograms of 3 (black), 5 (red) and 6 (green) in MeCN vs. Fc/Fc+ at room temperature (0.1 M [nBu4N][PF6]; v=250 mV s−1; Pt/[nBu4N][PF6]/Ag).
Figure 5
Figure 5
Absorption spectra of 2, 3, and 5 in MeCN/EtOH (4 : 1) at 298 K.
Figure 6
Figure 6
Emission spectra at absorption maximum 450 nm of 3 and 5 in MeCN/EtOH (4 : 1) at 298 K.
Scheme 7
Scheme 7
Carbon‐phosphorus photocatalytic cross‐coupling reported by Toste et al. and mechanistic scheme adapted from ref. 11; PC=photocatalyst.
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References

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