{
  "abstract": "Metal coordination provides an effective strategy for modulating the acidity of otherwise weak C–H bonds and controlling proton-transfer reactivity. Herein, we use density functional theory to investigate the effects of metal identity, tautomeric state, and substituent electronics on α-hydrogen acidity in metal-coordinated keto–enol systems. A systematic set of approximately 128 Au(III)-coordinated structures containing electron-donating and electron-withdrawing substituents was examined, with multiple coordination geometries and tautomeric forms considered to identify the thermodynamically preferred states. Au(III) coordination substantially enhances α-C–H acidity, with many systems exhibiting highly favorable deprotonation and strongly acidic computed pKa values. Electron-withdrawing substituents generally increase acidity, whereas electron-donating groups reduce it, although deviations observed for OMe and CF3 highlight the additional roles of charge delocalization and electrostatic stabilization. Kinetic analysis further reveals a strong dependence on tautomeric state: deprotonation of Au(III)-coordinated enol structures proceeds through barrierless pathways, whereas the corresponding keto structures require activation barriers of approximately 37–46 kcal mol−1. Comparative calculations with Co(III)-and Rh(III)-porphyrin complexes show substantially weaker acidification than Au(III), with both metals preferentially stabilizing the keto tautomer. These results demonstrate that metal identity, tautomeric structure, and substituent effects collectively govern α-C–H acidity and proton-transfer reactivity, highlighting the distinctive ability of Au(III) to promote α-hydrogen acidification in keto–enol systems.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Chemistry and Material Science, School of chemical Engineering",
    "Aalto University"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Amir Mahdian",
      "orcid": "0009-0006-0480-477X"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Kari Laasonen"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/e3xgwcqffetd8.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15010004/v1",
  "fulltext_url": null,
  "id": "e3xgwcqffetd8",
  "issns": [],
  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010004/v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "1605|Chemical Reaction Mechanisms"
    ]
  ],
  "openalex": "W7220834908",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15010004/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-06",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/e3xgwcqffetd8.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:22Z",
      "native_id": "10.26434/chemrxiv.15010004",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010004/v1"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "openalex:1605|Chemical Reaction Mechanisms",
      "subfield": "organic"
    }
  ],
  "title": "Transition-Metal-Controlled α-C–H Acidity in Keto–Enol Tautomers: A DFT Study of Metal, Tautomer, and Substituent Effects",
  "title_text": "Transition-Metal-Controlled α-C–H Acidity in Keto–Enol Tautomers: A DFT Study of Metal, Tautomer, and Substituent Effects",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:22Z",
  "url": "https://research.draconitic.com/paper/e3xgwcqffetd8",
  "venue": "ChemRxiv",
  "versions": []
}