Atypical and Asymmetric 1,3-P,N Ligands: Synthesis, Coordination and Catalytic Performance of Cycloiminophosphanes

Mark K. Rong, Flip Holtrop, Eduard O. Bobylev, Martin Nieger, Andreas W. Ehlers, J. Chris Slootweg, Koop Lammertsma*

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Novel seven-membered cyclic imine-based 1,3-P,N ligands were obtained by capturing a Beckmann nitrilium ion intermediate generated in situ from cyclohexanone with benzotriazole, and then displacing it by a secondary phosphane under triflic acid promotion. These “cycloiminophosphanes” possess flexible non-isomerizable tetrahydroazepine rings with a high basicity; this sets them apart from previously reported iminophophanes. The donor strength of the ligands was investigated by using their P-κ1- and P,N-κ2-tungsten(0) carbonyl complexes, by determining the IR frequency of the trans-CO ligands. Complexes with [RhCp*Cl2]2 demonstrated the hemilability of the ligands, giving a dynamic equilibrium of κ1 and κ2 species; treatment with AgOTf gives full conversion to the κ2 complex. The potential for catalysis was shown in the RuII-catalyzed, solvent-free hydration of benzonitrile and the RuII- and IrI-catalyzed transfer hydrogenation of cyclohexanone in isopropanol. Finally, to enable access to asymmetric catalysts, chiral cycloiminophosphanes were prepared from l-menthone, as well as their P,N-κ2-RhIII and a P-κ1-RuII complexes.

Original languageEnglish
Pages (from-to)14007-14016
Number of pages10
JournalChemistry - A European Journal
Issue number56
Early online date17 Aug 2021
Publication statusPublished - 7 Oct 2021

Bibliographical note

Funding Information:
This work was supported by the Council for Chemical Sciences of The Netherlands Organization for Scientific Research (NWO/CW). We thank T. van Dijk for measuring high resolution mass‐spectra and for fruitful discussions. M. K. Jongkind and R. Hoogendoorn are acknowledged for contributing to the synthesis of . A. Chirila and M. M. Heeren contributed to screening suitable Beckmann rearrangement substrates. 9

Publisher Copyright:
© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH

Copyright 2021 Elsevier B.V., All rights reserved.


  • cooperative effects
  • coordination modes
  • homogeneous catalysis
  • ligand design
  • N,P ligands


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