Skip to main content
NCBI home page
Scientific Reports logoLink to Scientific Reports
. 2026 Mar 18;16:14059. doi: 10.1038/s41598-026-43634-1

First time exploration and characterization of key-intermediates in palladium-catalysed coupling reactions

Péter Szuroczki 1,2,3, Attila Bényei 4, Rafael T Aroso 5, Mariette M Pereira 5,✉, László Kollár 1,2,3,✉
PMCID: PMC13136337  PMID: 41851341

Abstract

The oxidative addition of a bromoporphyrin onto in situ formed highly active Pd(0) complex allowed us to characterize the Pd(II) intermediate by X-ray crystallography. In addition, after the heterobidentate coordination of Xantphos hemioxide (Xantphos: 4,5-bis(diphenylphosphino)-9,9-dimethyl-xanthene), the oxidized product responsible for Pd(II)-Pd(0) reduction, was also proved. The species isolated by us is the product of oxidative addition, the first step of the suggested catalytic cycle. Earlier only the structure of the dichloro complex of palladium with (P-P(O)) ligand was known. The isolated Pd(P-P(O))X(porphyrinyl) complex can be considered as a new example of catalytic intermediates of important cross-coupling and carbonylation reactions giving further strong proof for their mechanism.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-026-43634-1.

Keywords: Palladium, Porphyrin, Phosphine, Oxidative addition, X-ray crystallography

Subject terms: Biochemistry, Chemistry

Introduction

The role of oxidative addition in transition metal chemistry cannot be overstated, given its central relevance in catalytic processes.1–3 The most important features include the increase in coordination number and oxidation state of the metal center, as well as a two-electron gain, which are thoroughly discussed in reviews and textbooks.4–9 As the first step in many catalytic cycles, oxidative addition has received particular attention in the 1970s and extensive mechanistic information had already been gathered on the role of low-valent transition metals (Ni(0), Pd(0)) with substrates such as aryl and benzyl halides.10,11

In the context of the Heck–Mizoroki12,13 and related cross-coupling reactions, Knowles and Whiting provided a detailed analysis of oxidative addition to Pd(0).14 It´s also well established that substrate activation in homogeneous, transition metal-catalyzed reactions proceeds through diverse pathways, depending on the electronic structures of both the metal center and the substrate. Generally, nonpolar substrates undergo oxidative addition via concerted mechanisms, yielding complexes where the new ligands occupy cis positions, typical of homogeneous hydrogenation and hydroformylation.15–18 In contrast, polar or electrophilic substrates react stepwise, forming trans intermediates in successive elementary steps. Cross-coupling reactions (Heck, Suzuki, Negishi, Kumada, Stille, Sonogashira) and their carbonylative variants, which revolutionized modern synthesis, follow this later stepwise pathway.19–23 In Pd-catalyzed cross-coupling, oxidative addition involves insertion of an aryl or alkenyl halide (or a sulfonate surrogate) into an in situ generated Pd(0)-phosphine species.24,25 It is worth noting that Ni(0) and Pt(0) precurzors of lower catalytic importance regarding the above reactions, have also been reacted with similar bromaromatics in oxidative addition.26–30 In general the Pt(II) complexes formed are kinetically less labile than the corresponding Pd-complexes.

As for the highly active palladium systems, both preformed Pd(0) precursors (Pd(PPh₃)₄), Pd2(dba)3) and Pd(II) sources (Pd(OAc)₂), PdCl2) can be used. It has also been shown that Pd(II) is reduced to Pd(0) by tertiary phosphines. Cyclic voltammetry studies revealed that PPh₃ is oxidized to triphenylphosphine oxide while the highly reactive, coordinatively unsaturated 14-electron Pd(0)-monophosphine species (indicated as ‘Pd(PPh3)(L)’, or in the presence of good donor solvents, ‘Pd(PPh3)(solvent)’) is formed (Fig. 1).31,32

Fig. 1.

Fig. 1

Open in a new tab

Formation of Pd(0) complexes from Pd(OAc)2 in the presence of PPh3 as reducing agent31,32.

Although monodentate phosphines dominate most cross-coupling protocols, bidentate ligands exhibit significant advantages.33,34 The key difference lies in geometry: with monodentate ligands, the oxidative addition product is usually trans, whereas bidentate chelates impose a cis configuration which is essential for efficient reductive elimination. However, the oxidation of bidentate phosphines during Pd(II) reduction generates “monodentate” phosphine–phosphine oxide ligands containing both P(III) and P(V) centers. NMR studies have supported the in situ formation of diphosphine hemi-oxides in Pd(II)-acetate/diphosphine systems.35

These phosphine–phosphine oxide ligands, although potentially capable of P,O-hemilable bidentate coordination, are generally regarded as monodentate. Consequently, statements such as “it is necessary to use at least two equivalents of a bidentate phosphine” are frequently encountered in the literature.14 This assumption, however, introduce both mechanistic and synthetic complications arising from the coexistence of mono- and dinuclear palladium species with mixed mono- and bidentate coordination modes.19–23,36 It is worth noting that the (partial) oxidation of diphosphines can be avoided by employing Pd(0) precursors such as tris(dibenzylideneacetone)dipalladium(0), (Pd₂(dba)₃) or Pd(dba)₂. However, in these systems, the coordinating dba ligand may inhibit the reaction by hindering oxidative addition.37

Regarding ligand selection, the seminal studies by van Leeuwen et al. on large bite-angle diphosphines are particularly noteworthy.38–41 The discovery of the Xantphos ligand family, which exhibit bite angles of 100–120°, had a profound impact on numerous transition metal-catalyzed reactions.42 As for carbonylation reactions, the work of Buchwald et al.on aryl bromide carbonylation with palladium-Xantphos in situ system has to be mentioned.43 Recently, highly active and selective Pd–Xantphos catalysts have been applied to aminocarbonylation (Heck–carbonylation) of haloaromatic substrates in our laboratory.44,45 Despite being repeatedly proposed as crucial intermediates in cross-coupling and carbonylation catalysis, Pd(diphosphine hemioxide)(halide)(aryl) complexes have never been experimentally observed or isolated. It is crucial, that herein, we report the first isolation and X-ray characterization of an in situ formed Pd(II)–Xantphos hemioxide complex containing a halide and a substrate (porphyrinyl) as ligands. This finding provides direct evidence for the heterobidentate coordination of the hemilabile P–P(O) ligand to a Pd(0) species (generated from a Pd(II) precursor) and for the oxidative addition of a bromo-porphyrin substrate to the Pd(0) center, thus revealing, for the first time, the structure of a long-hypothesized catalytic intermediate.

Results and discussion

As recently reported by us, a series of carboxamide-functionalised diphenylporphyrins (DPPs) with unprecedented structural features have been synthesized in good yields via palladium-catalysed carbonylation49 (Heck–carbonylation46–48). Under standard aminocarbonylation conditions (1 bar CO, 70 °C, Pd(OAc)₂ as catalyst precursor and 1 equivalent of Xantphos as ligand), several DPP-based mono- and dicarboxamides were obtained from DPP–Br₂ (1) as the substrate (Fig. 2).49 In addition, we have also been able to get a single-crystal of four of the porphyrin-based carboxamides, DPP-Bn, DPP-Gly, DPP-Gly2 and DPP-Ala2 (Fig. 3) and determine their structure by X-ray crystallography (See SI Fig. S1-4).

Fig. 2.

Fig. 2

Open in a new tab

A general scheme for the aminocarbonylation of DPP-Br2 (1)49.

Fig. 3.

Fig. 3

Open in a new tab

Porphyrin monocarboxamides (DPP-Bn and DPP-Gly) and dicarboxamides (DPP-Gly2 and DPP-Ala2) characterized by X-ray crystallography (for detailed information See SI Figures S1-4).

It is important to note that the Pd/Xantphos ratio of 1/1 was used throughout the catalytic investigations because of the following reasons: i) A perfectly homogeneous catalytic mixture was obtained even at the above low ratio of 1/1. ii) A highly active catalytic system was obtained and the addition of a second equivalent of Xantphos did not improve catalytic performance. In turn, previous investigations have shown that the use of Xantphos in twofold (or higher) excess has a deteriorative effect on activity.50 iii) The presence of diphosphine, as well as its dioxide and hemioxide in the final reaction mixture makes the work-up procedure, i.e., the isolation of the target product, more difficult.

From the catalytic reaction mixture of palladium catalysed carbonylation, using L-alanine methyl ester hydrocloride as nucleophile and DPP–Br₂ (1) as substrate, a crystalline chloro-porphyrinyl-palladium(II) complex (3) was formed and isolated.

The compound has been fully characterised including single-crystal X-ray crystallography (Fig. 4 and SI).

Fig. 4.

Fig. 4

Open in a new tab

X-ray crystal structure of 3. ORTEP view at 40% probability level, hydrogen atoms are omitted for clarity.

The structure of P-P(O) palladium complex 3 is remarkable and unprecedented. A search of the Cambridge Structural Database (Version 6.0, Update April 2025)51 revealed only one structurally related palladium complex (PdCl2(P-P(O)), ref. code WIGDOJ)52 and one zinc complex (ZnCl2(P-P(O)), ref. code VELPUB),53 both being dichloro complexes of the Xantphos hemioxide (P-P(O)) ligand. In our case, however, the chlorine atom trans to the coordinated oxygen is replaced by the porphyrin meso carbon atom (C15), allowing, for the first time, the structural characterization of a key intermediate in the catalytic cycle. Aside from this unique feature, the palladium centre adopts a typical square-planar coordination geometry, as evidenced by the bond distance and angle data (Table S3).

The following further features need to be emphasized. Although Pd(OAc)2/Xantphos in situ catalyst was used, the complex contains the hemioxide of Xantphos (abbreviated as P-P(O) in further discussion) coordinated as a hemilabile heterobidentate ligand. Its formation can be explained by the oxidation of the Xantphos diphosphine during the Pd(II)-Pd(0) reduction. While Pd(OAc)2 is reduced to a coordinatively highly unsaturated Pd(0) complex, one of the two phosphorus of the bidentate ligand is oxidised to phosphine oxide. Although the bidentate coordination of diphosphine hemioxide to Pd(II) has already been described,54,55 to the best of our knowledge, it is the first time to prove its presence in a catalytically active species (Fig. 5).

Fig. 5.

Fig. 5

Open in a new tab

X-ray crystal structure of 2, ORTEP view at 40% probability level, solvent chloroform as well as water molecule within the porphyrin ring and hydrogen atoms are omitted for clarity (only one enantiomer is shown).

According to a generally accepted mechanism of aminocarbonylation,56–67 the oxidative addition of 1 onto in situ formed Pd(0) complex should have resulted in the formation of a bromo-porphyrinyl-palladium(II) complex (2). However, the triethylammonium chloride salt, formed in the dehydrochlorination of methyl alaninate hydrochloride, acts as chloride source in bromo-chloro ligand exchange yielding 3 under catalytic conditions (Fig. 6).

Fig. 6.

Fig. 6

Open in a new tab

Oxidative addition of 1 onto palladium(0) species formed in situ from Pd(OAc)2 and Xantphos.

The above reaction sequence was proved by carrying out an independent experiment aiming at the direct synthesis of the bromo complex (2). In fact, reacting 1 with the in situ generated Pd(0) complex in the absence of a primary amine nucleophile, complex 2 was obtained. The efforts on crystallization led to good-quality needle-like crystals suitable for single-crystal X-ray crystallography which allowed us to unequivocally establish the molecular and crystal structure of the bromo-complex 2 (Fig. 5).

The structure of 2 is even more peculiar than that of 3. In this case the compound crystallized in a space group allowed for enantiomer pure compounds (monoclinic P21, Z = 4). We have a racemate, and the two enantiomers are in the asymmetric unit (Z’ = 2, Fig. 7) but at the same time the crystal is a racemic twin and that is indicated by the Flack parameter which is 0.5 within experimental error (F = 0.43). Compound 3 is also chiral and racemate, but in that case the space group is centrosymmetric (triclinic, P-1, Z = 2) with one enantiomer in the asymmetric unit (Z’ = 1) and the other enantiomer is generated by the lattice symmetry. The bond distance data for 2 and 3 (Table S3) are also reasonable for the P(O)-P ligand coordination.

Fig. 7.

Fig. 7

Open in a new tab

The two PdBr(Porph)(P-P(O)) enantiomers found in the asymmetric unit of structure 2. Solvent chloroform and water molecules within the porphyrine moieties are omitted for clarity.

Although only the oxidative addition (the ‘starting step’ of aminocarbonylation) was discussed above, it can be embedded in a widely accepted catalytic cycle (Fig. 8). The formation of carboxamides can be rationalised based on generally accepted sequence of steps such as oxidative addition of the substrate on Pd(P-P(O)), carbon monoxide activation as a terminal carbonyl ligand, its insertion into the palladium-carbon bond forming an acyl complex, coordination of the amin, the loss of hydrogen halide resulting in an amide-acyl complex, and reductive elimination in the closing (‘product-forming’) step.

Fig. 8.

Fig. 8

Open in a new tab

A proposed catalytic cycle of palladium-catalysed aminocarbonylation using bromoporphyrin as substrate and Xantphos as ligand.

Methods

General procedures

The Pd(OAc)2, Xantphos (4,5-bis(diphenylphosphino)-9,9-dimethylxanthene)), Et3N, all solvents, amines were purchased from Sigma-Aldrich (St. Louis, MO, USA) and were used without any further purification. The starting material (1) was prepared according to the reported protocol.68,69 All reactions were carried out under Ar using standard Schlenk techniques.

Precoated silica gel 60F254 plates were used for thin layer chromatography (TLC) and were also purchased from Sigma-Aldrich. Column chromatography was performed with 0.063–0.200 mm mesh silica gels. 1H, 13C and 31P NMR spectra were recorded in CDCl3 or DMSO-d6 on a Bruker Avance III 500 spectrometer (Bruker BioSpin Corp., Karlsruhe, Germany) at 500, 126 and 200 MHz, respectively. Chemical shifts δ are reported in ppm relative to CDCl3 (7.26 and 77.00 ppm for 1H and 13C, respectively), DMSO-d6 (2.50 and 39.50 ppm for 1H and 13C, respectively) or H3PO4 (85%) (0.00 ppm for 31P). The FT-IR spectra were taken in KBr pellets using a Nicolet IMPACT 400 spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) applying a DTGS detector in the region of 400–4000 cm-1, the resolution was 4 cm-1.

High-resolution mass spectra were acquired on a 6530 Accurate-Mass Quadrupole Time-of-Flight (Q-TOF) LC/MS system (Agilent Technologies, Singapore) equipped with an Agilent Jet Stream electrospray ionization (ESI) source.

X-ray crystallographic study

The unambiguous molecular structures of 2 and 3 have been established by X-ray diffraction analysis. X-ray quality crystals of both compounds were grown from the slow evaporation of concentrated solutions of n-hexane/chloroform standing at ambient temperature. A properly chosen suitable crystal was then fixed under a microscope onto a Mitegen loop using high-density oil. Diffraction Intensity data was collected at ambient temperature (294 K) on a Bruker-D8 Venture diffractometer (Bruker AXS GmbH, Karlsruhe, Germany) equipped with INCOATEC IµS 3.0 (Incoatec GmbH, Geesthacht, Germany) dual (Cu and Mo) sealed tube micro sources and a Photon II Charge-Integrating Pixel Array detector (Bruker AXS GmbH, Karlsruhe, Germany) using Mo Kα (λ = 0.71073 Å) radiation.

High-multiplicity data collection and integration were performed using APEX3 (version 2017.3–0, Bruker AXS Inc., 2017, Madison, WI, USA) software. Data reduction and multiscan absorption correction were performed using SAINT (version 8.38A, Bruker AXS Inc., 2017, Madison, WI, USA). The structure was solved using direct methods and refined on F2 using the SHELXL program70 incorporated into the APEX3 suite. Refinement was performed anisotropically for all non-hydrogen atoms. Hydrogen atoms were placed in idealized positions on parent atoms in the final refinement including adjacent hydrogen atoms within the porphyrin ring.

The CIF file was manually merged using publCIF software,71 while graphics were designed using the Mercury program.72 The results for the X-ray diffraction structure determinations followed the Checkcif functionality of PLATON software (Utrecht University, Utrecht, the Netherlands),73 and structural parameters, such as bond length and angle data, are in the expected range. The DPP compounds had high tendency to form twin crystals and in some cases the size of the crystals were very small, thin plate or needle. These features resulted in A and B level errors concerning the Rint and final R error data. However, all of the structures are considered to be correct and high importance in the field. Further details of the crystal parameters, data collection, and structure refinement are given in Table S1 and Table S2. The geometric parameters for all structures are given in Tables S3-S9.

The datasets generated and/or analysed during the current study are available in the Crystallographic Data Centre repository, http://www.ccdc.cam.ac.uk/data_request/cif using reference deposition numbers: 2512487 for 2 and 2512488 for 3 (Pd-complexes), as well as 2512489 for DPP-Bn, 2512490 for DPP-Gly, 2385880 for DPP-Gly2 and 2512491 for DPP-Ala2 (porphyrin carboxamides).

Conclusion

Most of the palladium-catalysed carbonylation and coupling reactions proceed via palladium(0) species enabling the activation of the substrate by its oxidative addition. In this work, the use of a bromoporphyrin substrate allowed us to characterize the porphyrin-Pd(II) intermediate by X-ray crystallography. In addition, the formation and heterobidentate coordination of Xantphos hemioxide, the oxidized product responsible for Pd(II)-Pd(0) reduction, was also proved. The isolated Pd(P-P(O))X(porphyrinyl) complexes can be considered as fully characterised new examples of catalytic intermediates and allow us to understand the nature of active catalysts.

Supplementary Information

Supplementary Information. (1.8MB, docx)

Acknowledgements

The research reported in this paper is part of project no. TKP2021-EGA-17, implemented with the support provided by the Ministry of Innovation and Technology of Hungary from the National Research Development and Innovation Fund financed under the TKP2021 funding scheme. The research was supported by the EU and co-financed by the European Regional Development Fund under the project GINOP-2.3.2-15-2016-00008 and also under the project GINOP-2.3.3-15-2016-00004 to purchase the diffractometer at the University of Debrecen. The Coimbra Chemistry Centre-Institute of Molecular Sciences (CQC-IMS) is supported by national funds from Fundação para a Ciência e a Tecnologia (FCT) through projects UIDB/00313/2025 and UIDP/00313/2025 and LA/P/0056/2020 (10.54499/LA/P/0056/2020). This research was also funded by project “ECOXOPLAS” n. 15161 (COMPETE2030-FEDER-00882400).

Author contributions

P.S. carried out the catalytic experiments and isolated the complexes as crystals A.B. determined the crystal structures and wrote the discusssion on XRD R.A. prepared the porphyrins M.M.Pereira reviewed the manuscript L.K. wrote the main text.

Funding

Open access funding provided by University of Pécs. The authors declare funding by the Ministry of Innovation and Technology of Hungary, by the European Regional Development Fund, and by Fundação para a Ciência e a Tecnologia (FCT, Portugal).

Data availability

The datasets generated and/or analysed during the current study are available in the Crystallographic Data Centre repository, http://www.ccdc.cam.ac.uk/data_request/cif using reference deposition numbers: 2512487 for 2 and 2,512,488 for 3, as well as 2,512,489 for DPP-Bn, 2,512,490 for DPP-Gly, 2,385,880 for DPP-Gly2 and 2,512,491 for DPP-Ala2. In addition to analytical data (1H and 13C NMR, MS) discussed in Supplementary Information, further details are available from the authors upon request.

Declarations

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Contributor Information

Mariette M. Pereira, Email: mmpereira@qui.uc.pt

László Kollár, Email: kollar@gamma.ttk.pte.hu.

References

  • 1.Beller, M., Bolm, C. Transition Metals for Organic Synthesis: Building Blocks and Fine Chemicals, Wiley-VCH, (2004)
  • 2.Beller, M., Wu, X.-F. Transition Metal Catalyzed Carbonylation Reactions: Carbonylative Activation of C-X Bonds, Springer-Verlag (2013)
  • 3.Cornils, B., Herrmann, W. A., Beller, M., Paciello, R. Applied Homogeneous Catalysis with Organometallic Compounds: A Comprehensive Handbook in Four Volumes, Third edition, Wiley‐VCH (2017).
  • 4.Miessler, G. L., Tarr, D. A. Inorganic Chemistry, Third edition, Pearson Prentice Hall (2004)
  • 5.Shriver, D. F., Atkins, P. W. Inorganic Chemistry, Tthird edition, Oxford University Press (1999)
  • 6.Crabtree, R. The Organometallic Chemistry of The Transition Metals (Wiley-Interscience, 2005). [Google Scholar]
  • 7.Hartwig, J. F. Organotransition Metal Chemistry: from Bonding to Catalysis. University Science Books (2010)
  • 8.Labinger, J. A. Tutorial on oxidative addition. Organometallics34, 4784–4795 (2015). [Google Scholar]
  • 9.Elschenbroich, C., Salzer, A. Organometallics. A Concise Introduction, Second edition, Wily-VCH (1992).
  • 10.Tsou, T. T. & Kochi, J. K. Mechanism of oxidative addition. Reaction of nickel(0) complexes with aromatic halides. J. Am. Chem. Soc.101, 6319–6332 (1979). [Google Scholar]
  • 11.Lau, K. S. Y., Wong, P. K. & Stille, J. K. Oxidative addition of benzyl halides to zero-valent palladium complexes. Inversion of configuration at carbon. J. Am. Chem. Soc.98, 5832–5840 (1976). [Google Scholar]
  • 12.Heck, R. F. & Nolley, J. P. Jr. Palladium-catalyzed vinylic hydrogen substitution reactions with aryl, benzyl, and styryl halides. J. Org. Chem.37, 2320–2322 (1972). [Google Scholar]
  • 13.Mizoroki, T., Mori, K. & Ozaki, A. Arylation of olefin with aryl iodide catalyzed by palladium. Bull. Chem. Soc. Jpn.44, 581–581 (2006). [Google Scholar]
  • 14.Knowles, J. P. & Whiting, A. The Heck–Mizoroki cross-coupling reaction: A mechanistic perspective. Org. Biomol. Chem.5, 31–44 (2007). [DOI] [PubMed] [Google Scholar]
  • 15.O'Connor, C., Wilkinson, G. Selective homogeneous hydrogenation of alk-1-enes using hydridocarbonyltris(triphenylphosphine)rhodium(I) as catalyst. Journal of the Chemical Society A: Inorganic, Physical, Theoretical 2665–2671 (1968)
  • 16.Yagupsky, G., Brown, C., Wikinson, G. Intermediates or their analogues in hydroformylation of alkenes catalysed by hydridocarbonyltris(triphenylphosphine)rhodium(I). Journal of the Chemical Society D: Chemical Communications 1244–1245 (1969)
  • 17.Halpern, J. Mechanistic aspects of homogeneous catalytic hydrogenation and related processes. Inorg. Chim. Acta50, 11–19 (1981). [Google Scholar]
  • 18.Schrock, R. R., Osborn, J. A. Catalytic hydrogenation using cationic rhodium complexes. I. Evolution of the catalytic system and the hydrogenation of olefins. Journal of the American Chemical Society 98, 2134–2143 (1976).
  • 19.Diederich, F. & de Mejiere, A. Metal Catalysed Cross-Coupling Reactions Second edition. (Wiley-VCH, 2004). [Google Scholar]
  • 20.Ananikov, V. P., Musaev, D. G. & Morokuma, K. Theoretical insight into the C−C coupling reactions of the vinyl, phenyl, ethynyl, and methyl complexes of palladium and platinum. Organometallics24, 715–723 (2005). [Google Scholar]
  • 21.Corbet, J.-P. & Mignani, G. Selected patented cross-coupling reaction technologies. Chem. Rev.106, 2651–2710 (2006). [DOI] [PubMed] [Google Scholar]
  • 22.Johansson Seechurn, C. C. C., Kitching, M. O., Colacot, T. J. & Snieckus, V. Palladium-catalyzed cross-coupling: A historical contextual perspective to the 2010 Nobel Prize. Angew. Chem. Int. Ed.51, 5062–5085 (2012). [DOI] [PubMed] [Google Scholar]
  • 23.Korch, K. M. & Watson, D. A. Cross-coupling of heteroatomic electrophiles. Chem. Rev.119, 8192–8228 (2019). [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Arnold, D. P.; Sakata, Y.; Sugiura, K.; Worthington, E. I. meso-η1-Metalloporphyrins: Preparation of Palladio- and Platinioporphyrins and the Crystal Structure of 5-[Bromo-1,2-Bis(diphenylphosphino)-ethanepalladio(II)-10,20-Diphenylporphyrin. Chem. Commun. 2331−2332 (1998)
  • 25.Arnold, D. P.; Healy, P. C.; Hodgson, M. J.; Williams, M. L. Peripherally-Metalated Porphyrins: Synthesis and Spectra of meso-η1-Palladio- and Platinioporphyrins and the Crystal Structures of cis-{PtBr[10,20-Diphenylporphyrinatonickel(II)-5-yl](PPh3)2} and trans-{PtBr[10,20-Diphenylporphyrin-5-yl](PPh3)2}·0.25CH2Cl2. J. Organomet. Chem. 607, 41−50 (2000).
  • 26.Hartnell, R. D.; Arnold, D. P. Peripherally Metallated Porphyrins: The First Examples of meso-η1-Palladio(II) and -Platinio-(II) Complexes with Chelating Diamine Ligands. Eur. J. Inorg. Chem. 1262−1269 (2004)
  • 27.Hodgson, M. J.; Healy, P. C.; Williams, M. L.; Arnold, D. P. Peripherally-Metalated Porphyrins: Preparations, Spectroscopic Properties and Structural Studies of trans-[PtBr(MDPP) (PPh3)2] (DPP = Dianion of 5,15-Diphenylporphyrin, M = MnCl, Co, Ni, Zn) and Related meso-η1-Organoplatinum Porphyrins. J. Chem. Soc., Dalton Trans. 4497−4504 (2002)
  • 28.Hodgson, M. J., Borovkov, V. V., Inoue, Y. & Arnold, D. P. A new type of chiral porphyrin: Organopalladium porphyrins with chiral chelating diphosphine ligands. J. Organomet. Chem.691, 2162–2170 (2006). [Google Scholar]
  • 29.Hartnell, R. D., Edwards, A. J. & Arnold, D. P. Peripherally-metalated porphyrins: meso-η1-Porphyrinylplatinum(II) complexes of 5,15-diaryl- and 5,10,15-triarylporphyrins. J. Porphyrins Phthalocyanines6, 695–707 (2002). [Google Scholar]
  • 30.Hartnell, R. D. & Arnold, D. P. Peripherally η1-platinated organometallic porphyrins as building blocks for multiporphyrin arrays. Organometallics23, 391–399 (2004). [Google Scholar]
  • 31.Amatore, C., Jutand, A. & M’Barki, M. A. Evidence of the formation of zerovalent palladium from Pd(OAc)2 and triphenylphosphine. Organometallics11, 3009–3013 (1992). [Google Scholar]
  • 32.Amatore, C., Carre, E., Jutand, A., M’Barki, M. A. & Meyer, G. Evidence for the ligation of palladium(0) complexes by acetate ions: Consequences on the mechanism of their oxidative addition with phenyl iodide and PhPd(OAc)(PPh3)2 as intermediate in the Heck reaction. Organometallics14, 5605–5614 (1995). [Google Scholar]
  • 33.Jover, J. et al. Expansion of the Ligand Knowledge Base for Monodentate P-Donor Ligands (LKB-P). Organometallics29, 6245–6258 (2010). [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34.Jover, J. et al. Expansion of the Ligand Knowledge Base for Chelating P,P-Donor Ligands (LKB-PP). Organometallics31, 5302–5306 (2012). [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 35.Csákai, Z., Skoda-Földes, R. & Kollár, L. NMR investigation of Pd(II)–Pd(0) reduction in the presence of mono- and ditertiary phosphines. Inorg. Chim. Acta286, 93–97 (1999). [Google Scholar]
  • 36.Amatore, C., Jutand, A. & Thuilliez, A. Formation of palladium(0) complexes from Pd(OAc)2 and a bidentate phosphine ligand (dppp) and their reactivity in oxidative addition. Organometallics20, 3241–3249 (2001). [Google Scholar]
  • 37.Amatore, C., Broeker, G., Jutand, A., Khalil, F. Identification of the Effective Palladium(0) Catalytic Species Generated in Situ from Mixtures of Pd(dba)2 and Bidentate Phosphine Ligands. Determination of Their Rates and Mechanism in Oxidative Addition. Journal of the American Chemical Society 119: 5176–5185 (1997).
  • 38.van Leeuwen, P. W. N. M. v., Kamer, P. C. J., Reek, J. N. H. The bite angle makes the catalyst. Pure and Applied Chemistry 71, 1443–1452 (1999)
  • 39.van Leeuwen, P. W. N. M., Kamer, P. C. J., Reek, J. N. H. & Dierkes, P. Ligand bite angle effects in metal-catalyzed C−C bond formation. Chem. Rev.100, 2741–2770 (2000). [DOI] [PubMed] [Google Scholar]
  • 40.Kamer, P. C. J., van Leeuwen, P. W. N. M. & Reek, J. N. H. Wide bite angle diphosphines: Xantphos ligands in transition metal complexes and catalysis. Acc. Chem. Res.34, 895–904 (2001). [DOI] [PubMed] [Google Scholar]
  • 41.van der Veen, L. A., Keeven, P. K., Kamer, P. C. J., van Leeuwen, P. W. N. M. Wide bite angle amine, arsine and phosphine ligands in rhodium- and platinum/tin-catalysed hydroformylation. Journal of the Chemical Society, Dalton Transactions, 2105–2112 (2000).
  • 42.Yin, J. & Buchwald, S. L. Pd-catalyzed intermolecular amidation of aryl halides: The discovery that Xantphos can be trans-chelating in a palladium complex. J. Am. Chem. Soc.124, 6043–6048 (2002). [DOI] [PubMed] [Google Scholar]
  • 43.Martinelli, J. R., Watson, D. A., Freckmann, D. M. M., Barder, T. E. & Buchwald, S. L. Palladium-catalyzed carbonylation reactions of aryl bromides at atmospheric pressure: A general system based on Xantphos. J. Org. Chem.73, 7102–7107 (2008). [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 44.Kollár, L., Ince, N. U., Zugó, A., Dörnyei, Á. & Takács, A. Selective synthesis of Isoquinoline-1-Carboxamides via palladium-catalyzed aminocarbonylation in DMF and biomass-derived solvents. Catalysts15, 78 (2025). [Google Scholar]
  • 45.Uzunlu Ince, N. et al. Alkyl 4-Alkoxyvalerates: Characterization and application in Pd-catalyzed aminocarbonylation of iodo(hetero)arene compounds. ChemPlusChem90, e202400713 (2025). [DOI] [PubMed] [Google Scholar]
  • 46.Schoenberg, A. & Heck, R. F. Palladium-catalyzed amidation of aryl, heterocyclic, and vinylic halides. J. Org. Chem.39, 3327–3331 (1974). [Google Scholar]
  • 47.Schoenberg, A., Bartoletti, I. & Heck, R. F. Palladium-catalyzed carboalkoxylation of aryl, benzyl, and vinylic halides. J. Org. Chem.39, 3318–3326 (1974). [Google Scholar]
  • 48.Schoenberg, A. & Heck, R. F. Palladium-catalyzed formylation of aryl, heterocyclic, and vinylic halides. J. Am. Chem. Soc.96, 7761–7764 (1974). [Google Scholar]
  • 49.Szuroczki, P. et al. Unlocking new porphyrin aminoacid bioconjugates with a Pd-catalyzed carboxamide synthesis. ChemPlusChem90, e202500193 (2025). [DOI] [PubMed] [Google Scholar]
  • 50.Klingensmith, L. M., Strieter, E. R., Barder, T. E. & Buchwald, S. L. New insights into Xantphos/Pd-catalyzed C−N bond forming reactions: A structural and kinetic study. Organometallics25, 82–91 (2006). [Google Scholar]
  • 51.Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. The Cambridge structural database. Acta Crystallogr. B72, 171–179 (2016). [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 52.Ding, Y., Wu, J. & Huang, H. Carbonylative formal cycloaddition between alkylarenes and aldimines enabled by palladium-catalyzed double C–H bond activation. J. Am. Chem. Soc.145, 4982–4988 (2023). [DOI] [PubMed] [Google Scholar]
  • 53.Zhao, L., Dong, Y., Xia, Q., Bai, J. & Li, Y. Zn-catalyzed cyanation of aryl iodides. J. Org. Chem.85, 6471–6477 (2020). [DOI] [PubMed] [Google Scholar]
  • 54.Gladiali, S., Medici, S., Kégl, T. & Kollàr, L. Synthesis, characterization, and catalytic activity of Rh(I) complexes with (S)-BINAPO, an axially chiral inducer capable of hemilabile P,O-heterobidentate coordination. Monatsh. Chem.131, 1351–1361 (2000). [Google Scholar]
  • 55.Gladiali, S., Alberico, E., Pulacchini, S. & Kollàr, L. Synthesis, characterization and use in enantioselective hydroformylation of (BINAPO)PtCl2 (BINAPO=2-diphenylphosphino-2′-diphenylphosphinyl-1,1′-binaphthalene), the first chiral catalyst with an atropisomeric hemilabile P,O-heterodonor ligand. J. Mol. Catal. A Chem.143, 155–162 (1999). [Google Scholar]
  • 56.Wu, X.-F., Neumann, H. & Beller, M. Synthesis of heterocycles via palladium-catalyzed carbonylations. Chem. Rev.113, 1–35 (2013). [DOI] [PubMed] [Google Scholar]
  • 57.Roy, S., Roy, S. & Gribble, G. W. Metal-catalyzed amidation. Tetrahedron68, 9867–9923 (2012). [Google Scholar]
  • 58.Wu, X.-F., Neumann, H. & Beller, M. Palladium-catalyzed carbonylative coupling reactions between Ar–X and carbon nucleophiles. Chem. Soc. Rev.40, 4986–5009 (2011). [DOI] [PubMed] [Google Scholar]
  • 59.Magano, J. & Dunetz, J. R. Large-scale applications of transition metal-catalyzed couplings for the synthesis of pharmaceuticals. Chem. Rev.111, 2177–2250 (2011). [DOI] [PubMed] [Google Scholar]
  • 60.Grigg, R. & Mutton, S. P. Pd-catalysed carbonylations: Versatile technology for discovery and process chemists. Tetrahedron66, 5515–5548 (2010). [Google Scholar]
  • 61.Brennführer, A., Neumann, H. & Beller, M. Palladium-catalyzed carbonylation reactions of aryl halides and related compounds. Angew. Chem. Int. Ed.48, 4114–4133 (2009). [DOI] [PubMed] [Google Scholar]
  • 62.Barnard, C. F. J. Palladium-catalyzed carbonylation—A reaction come of age. Organometallics27, 5402–5422 (2008). [Google Scholar]
  • 63.Skoda-Foldes, R. & Kollar, L. Synthetic applications of palladium catalysed carbonylation of organic halides. Curr. Org. Chem.6, 1097–1119 (2002). [Google Scholar]
  • 64.Wu, X.-F., Neumann, H. & Beller, M. Selective palladium-catalyzed aminocarbonylation of aryl halides with CO and ammonia. Chem. Eur. J.16, 9750–9753 (2010). [DOI] [PubMed] [Google Scholar]
  • 65.Gadge, S. T. & Bhanage, B. M. Recent developments in palladium catalysed carbonylation reactions. RSC Adv.4, 10367–10389 (2014). [Google Scholar]
  • 66.Wu, X.-F. Palladium-catalyzed carbonylative transformation of aryl chlorides and aryl tosylates. RSC Adv.6, 83831–83837 (2016). [Google Scholar]
  • 67.Peng, J.-B., Qi, X. & Wu, X.-F. Recent achievements in carbonylation reactions: A personal account. Synlett28, 175–194 (2017). [Google Scholar]
  • 68.DiMagno, S. G., Lin, V. S. Y. & Therien, M. J. Facile elaboration of porphyrins via metal-mediated cross-coupling. J. Org. Chem.58, 5983–5993 (1993). [Google Scholar]
  • 69.Manka, J. S. & Lawrence, D. S. High yield synthesis of 5,15-diarylporphyrins. Tetrahedron Lett.30, 6989–6992 (1989). [Google Scholar]
  • 70.Sheldrick, G. A short history of SHELX. Acta Crystallogr. A64, 112–122 (2008). [DOI] [PubMed] [Google Scholar]
  • 71.Westrip, S. publCIF: Software for editing, validating and formatting crystallographic information files. J. Appl. Crystallogr.43, 920–925 (2010). [Google Scholar]
  • 72.Macrae, C. F. et al. Mercury 4.0: From visualization to analysis, design and prediction. J. Appl. Crystallogr.53, 226–235 (2020). [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 73.Spek, A. L. PLATON, An integrated tool for the analysis of the results of a single crystal structure determination. Acta Crystallogr. A46, 34–34 (1990). [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplementary Information. (1.8MB, docx)

Data Availability Statement

The datasets generated and/or analysed during the current study are available in the Crystallographic Data Centre repository, http://www.ccdc.cam.ac.uk/data_request/cif using reference deposition numbers: 2512487 for 2 and 2,512,488 for 3, as well as 2,512,489 for DPP-Bn, 2,512,490 for DPP-Gly, 2,385,880 for DPP-Gly2 and 2,512,491 for DPP-Ala2. In addition to analytical data (1H and 13C NMR, MS) discussed in Supplementary Information, further details are available from the authors upon request.

Articles from Scientific Reports are provided here courtesy of Nature Publishing Group

RESOURCES