{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T15:44:07Z","timestamp":1769010247947,"version":"3.49.0"},"reference-count":25,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2022,7,25]],"date-time":"2022-07-25T00:00:00Z","timestamp":1658707200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>The successful use of 1,3,4,2-triazaphospholenes (TAPs) as organo-catalysts stresses the need for efficient synthetic routes to these molecules. In this study, we establish the [1 + 4]-cycloaddition of PBr3 to azo-pyridines as a new approach to preparing pyrido-annellated TAPs in a single step from easily available precursors. The modular assembly of the azo-component via condensation of primary amines and nitroso compounds along with the feasibility of post-functionalization at the P\u2013Br bond under conservation of the heterocyclic structure allows, in principle, to address a wide range of target molecules, which is illustrated by prototypical examples. The successful synthesis of a transition metal complex confirms for the first time the ability of a TAP to act as a P-donor ligand. Crystallographic studies suggest that hyperconjugation effects and intermolecular interactions induce a qualitatively similar ionic polarization of the P\u2013Br bonds in TAPs as in better known isoelectronic diazaphospholenes.<\/jats:p>","DOI":"10.3390\/molecules27154747","type":"journal-article","created":{"date-parts":[[2022,7,25]],"date-time":"2022-07-25T21:20:59Z","timestamp":1658784059000},"page":"4747","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Annellated 1,3,4,2-Triazaphospholenes-Simple Modular Synthesis and a First Exploration of Ligand Properties"],"prefix":"10.3390","volume":"27","author":[{"given":"Ferdinand","family":"Richter","sequence":"first","affiliation":[{"name":"Institut f\u00fcr Anorganische Chemie, University of Stuttgart, 70550 Stuttgart, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nicholas","family":"Birchall","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Anorganische Chemie, University of Stuttgart, 70550 Stuttgart, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Christoph M.","family":"Feil","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Anorganische Chemie, University of Stuttgart, 70550 Stuttgart, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Martin","family":"Nieger","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Helsinki, FIN-00014 Helsinki, Finland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9196-0466","authenticated-orcid":false,"given":"Dietrich","family":"Gudat","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Anorganische Chemie, University of Stuttgart, 70550 Stuttgart, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,7,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1007\/7081_2009_5","article-title":"Recent Developments in the Chemistry of N-Heterocyclic Phosphines","volume":"21","author":"Gudat","year":"2010","journal-title":"Top. 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