Tricoordinate Coinage Metal Complexes with a Redox‐Active Tris‐(Ferrocenyl)triazine Backbone Feature Triazine–Metal Interactions

Abstract

2,4,6-Tris(1-diphenylphosphanyl-1'-ferrocenylene)-1,3,5-triazine (1)c oordinates all three coinage metal(I) ions in a1 :1 tridentate coordination mode. The C 3 -symmetric coordination in both solids tate and solution is stabilisedb ya nu ncommon cation-p interaction between the triazine core and the metal cation. Intramolecular dynamic behaviour was observed by variable-temperature NMR spectroscopy.T he borane adduct of 1, 1BH 3 , displays four accessible oxidation states, suggesting complexes of 1 to be intriguing candidates for redox-switchable catalysis. Complexes 1Cu, 1Ag,a nd 1Au display a more complicated electrochemical behaviour,a nd the electrochemical mechanism was studied by temperatureresolved UV/Vis spectroelectrochemistry and chemical oxidation.Scheme1.Preparation of tris-phosphane 1 andits corresponding coinage metal complexes 1Cu, 1Ag,and 1Au.I solated yields are given in brackets. À-basedS E; arrowsd enote the startingp otentialand initial scan direction at 100 mV s À1 .The secondo fthreeconsecutively measured cycles is shownifnot noted otherwise. Bottomr ight: Equilibrium between two coordination isomersof1Cu in solution.

The core of the matter – arene substitution determines the coordination and catalytic behaviour of tris(1-phosphanyl-1′-ferrocenylene)arene gold(i) complexes

“…69 The dynamic behaviour mirrors that of a similarly dicoordinating tris-phosphane by Wade and Gabbaï. 66 In contrast to triazine-based [1a(Au)]OTf, 35 the low-temperature 1 H NMR spectra of [1b(Au)]OTf (Fig. S43 †) do not give rise to well-defined sharp resonances.…”

“…Building on the observation of 1a forming trigonal-planar mononuclear complexes with the coinage metals, 35 we first investigated the analogous reaction of benzene-based 1b with halide-free gold(I) precursor [Au(η 2 -nbe) 3 ]OTf (nbe = nornbornene). Gold(I), in contrast to copper(I) and silver(I), [52][53][54] tends to be coordinated by arenes in an η 2 fashion with impact on asymmetric induction and catalyst stability.…”

“…In the corresponding complex of 1a, the silver(I)-π(C 3 N 3 ) interaction had been found stronger than for the gold(I) analogue. 35 While the formation and isolation of [1a F (Ag)]OTf proved much more facile, the solid-state molecular structure (Fig. 4, bottom) is analogous to that of the gold(I) congener.…”

“…As previously noted for isostructural pairs of silver(I) and gold(I) complexes, the M-P bonds (Table 2) are longer for the silver(I) complex. 35,71,105 The P(1)-Ag(1)-P(2) bond angle deviates more strongly from the ideal 180°, paralleled by a shorter Ag 1 [1a F (Ag)]OTf is, to the best of our knowledge, the first silver complex of a pentafluorophenylphosphane (one example of a corresponding phosphanido complex, formed by C 6 F 5 group transfer from AgC 6 F 5 to a PCl 2 moiety, has been reported by Schulz and co-workers). 106 Despite their similar structures, the silver(I) complex deviates from the gold(I) analogue in its (VT) NMR-spectroscopic features (Fig.…”

“…[28][29][30][31] Conceived as small-molecule analogues of redox-switchable dendrimers, [32][33][34] we have recently reported the synthesis of a new family of tris-phosphanes 1 (Chart 1) incorporating a redox-active, C 3 -symmetric tris(ferrocenyl)arene backbone. 35 Capable of forming both mono-and trinuclear gold(I) complexes (Chart 2), the latter were shown to act as four-state redox-switchable catalysts. The tris-phosphanes are prepared in a modular fashion, and s-triazine, benzene, and 1,3,5-trifluorobenzene have been used as central arenes.…”