Dispersion, solvent and metal effects in the binding of gold cations to alkynyl ligands: implications for Au(i) catalysis

Abstract

The coordination modes of the [Au(PPh3)](+) cation to metal alkynyl complexes have been investigated. On addition to ruthenium, a vinylidene complex, [Ru(η(5)-C5H5)(PPh3)2([double bond, length as m-dash]C[double bond, length as m-dash]CPh{AuPPh3})](+), is obtained while addition to a gold(iii) compound gives di- and trinuclear gold complexes depending on the conditions employed. In the trinuclear species, a gold(i) cation is sandwiched between two gold(iii) alkynyl complexes, suggesting that coordination of multiple C-C triple bonds to gold is facile.

Role of σ,π-Digold(I) Alkyne Complexes in Reactions of Enynes

“… , Complexes of this type with nonterminal alkynes have been structurally characterized. − Alternatively, deprotonation of the terminal alkyne by the counterion X – can generate σ-alkynyl gold­(I) complexes 2 . Acetylides 2 react with 1 or with the initial catalyst [AuLL′]­X to form finally σ,π-digold­(I) alkyne digold­(I) complexes 3 , − which are stable species that have been structurally characterized. − The facile formation of complexes 3 is a result of the stronger binding of gold­(I) to acetylides 2 than to free alkynes…”

Synthesis, mesomorphism, photophysics and device performance of liquid-crystalline pincer complexes of gold(iii)

“…Similar selfassociation has been postulated previously in a number of systems. 20,55 The resonances for the acetylide ligand showed only a very small and opposite shift (H h and H i ) or no concentration dependence (H e ). This would appear to indicate that any intermolecular process involving this region of the complex is different from that mediated by the C^N^C ligands.…”

Computational mechanistic study in organometallic catalysis: Why prediction is still a challenge

“…8,[18][19][20][21] Going forward, new semi-empirical/tight-binding approaches are likely to improve this aspect of exploring the relevant potential and free energy surfaces further, with improved agreement with DFT calculations potentially streamlining the evaluation of multiple options. [21][22][23][24][25] As we will show below, reliable comparison of competing reaction pathways remains challenging even with goodquality DFT, 261 with different functionals at times leading to conflicting predictions, 27 but experimental insights and/or calibration against calculations at higher levels of theory may serve to tension the data where DFT accuracy alone is uncertain or insufficient. Furthermore, as recently highlighted by Brakestad et al 28 calculations of this type have an error associated with the basis set.…”

“…In an attempt to synthesize stable gold vinylidene complexes rooted in computational prediction, 27,75 we found that CNC pincer ligands were able to stabilize unusual trinuclear gold complexes as shown in Scheme 6. 27 While intramolecular and intermolecular π-stacking interactions from the pincer ligands facilitated the isolation of these complexes, likely making them a thermodynamic sink, calculations predicted that related PPh 3 -ligated gold complexes might also be energetically accessible, even though the dinuclear σ-π complexes ([5]SbF 6 in Scheme 5) were predicted to be more favorable (albeit only by 6-8 kJ/mol). We used ESI-MS and 13 C-enriched NMR spectroscopy to detect a trinuclear gold alkynyl complex with PPh 3 ligands in situ, highlighting how such techniques can be used to tension calculated data against experimental reality.…”