Phosphorus Ligands for the Stabilization of Unusual and Elusive Structures in Transition Metal Complexes

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Coordination Chemistry".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 10310

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Instituto de Investigaciones Químicas (IIQ), Departamento de Química, Inorgánica and Centro de Innovación en Química Avanzada (ORFEO−CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Avenida Américo Vespucio 49, 41092 Sevilla, Spain
Interests: phosphorus(III) ligands; coordination chemistry; organometallic chemistry; late transition metals; low coordinate complexes

Special Issue Information

Dear Colleagues,

Phosphines and related P(III) ligands constitute one of the most-used classes of ligands in coordination and organometallic chemistry and have great potential for application in homogeneous catalysis. Their electronic and steric characteristics can easily be tuned by varying the three substituents on the phosphorus atom, thus covering an ample range of properties that span from small strong σ-donating ligands such as PMe3 to bulky less-basic π-accepting ligands such as tris(o-tolyl)phosphite. P(III) ligands, in either the monodentate form or a polydentate/hybrid form, have played a crucial role in the stabilization of elusive species and unusual structures within transition complexes, allowing for the isolation and/or detection of agostic complexes, σ-alkane adducts, non-heteroatom-stabilized alkylidenes, and low-coordinate unsaturated species, among others. With this Special Issue, we aim to present a collection of research and review articles dedicated to the design and applications of phosphines and related ligands, with special reference to the stabilization of elusive and unusual structural motifs in transition metal complexes.

Prof. Dr. Riccardo Peloso
Guest Editor

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Keywords

  • phosphorus ligands
  • ligands design
  • unsaturated complexes
  • low-coordinate complexes
  • agostic complexes
  • transition metal complexes
  • σ-complexes
  • phosphine
  • phosphite
  • phosphonite
  • phosphinite

Published Papers (6 papers)

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Research

20 pages, 5101 KiB  
Article
A Single Biaryl Monophosphine Ligand Motif—The Multiverse of Coordination Modes
by Barbara Miroslaw, Izabela Dybala, Radomir Jasiński and Oleg M. Demchuk
Inorganics 2023, 11(10), 399; https://doi.org/10.3390/inorganics11100399 - 11 Oct 2023
Viewed by 1054
Abstract
Biaryl monophosphines are important precursors to active catalysts of palladium-mediated cross-coupling reactions. The efficiency of the phosphine-based transition metal complex catalyst has its origin in the electronic structure of the complex used and the sterical hindrance created by the ligand at an active [...] Read more.
Biaryl monophosphines are important precursors to active catalysts of palladium-mediated cross-coupling reactions. The efficiency of the phosphine-based transition metal complex catalyst has its origin in the electronic structure of the complex used and the sterical hindrance created by the ligand at an active catalyst site. The aim of this paper is to shed some light on the multiverse of coordination modes of biaryl monophosphine ligands. Here, we present the analysis of the X-ray single crystal structures of palladium(II) complexes of a family of biaryl monophosphine ligands and the first crystallographic report on a related phosphine sulfide. Despite the common biaryl monophosphine ligand motif, they show diverse coordination modes (i) starting from the activation of aromatic C atoms and producing a C,P metallacycle, through (ii) the O,P chelation to Pd(II) ions with a simultaneous demethylation reaction of one of the methoxy groups, ending up with (iii) the monodentate coordination to metal cations via P atoms or (iv) via S atoms in the case of phosphine sulfide. We relate our results to the crystal structures found in the Cambridge Structural Database to show the multiverse of coordination modes in the group of biaryl monophosphine ligands. Full article
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11 pages, 1654 KiB  
Article
Dibromo- and Dichlorotriphenylphosphino N-Acyclic Carbene Complexes of Platinum(II)—Synthesis and Cytotoxicity
by Anna Farasat, Luca Labella, Maria Luisa Di Paolo, Lisa Dalla Via and Simona Samaritani
Inorganics 2023, 11(9), 365; https://doi.org/10.3390/inorganics11090365 - 8 Sep 2023
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Abstract
Some new dichloro- and dibromotriphenylphosphino isonitrile and N-acyclic (NAC) carbene complexes of platinum(II) were synthesized, starting from suitable dinuclear precursors. The reaction of cyclohexylisonitrile with trans-[Pt(μ-X)X(PPh3)]2, followed by the addition of N,N-diethylamine afforded the corresponding N-acyclic [...] Read more.
Some new dichloro- and dibromotriphenylphosphino isonitrile and N-acyclic (NAC) carbene complexes of platinum(II) were synthesized, starting from suitable dinuclear precursors. The reaction of cyclohexylisonitrile with trans-[Pt(μ-X)X(PPh3)]2, followed by the addition of N,N-diethylamine afforded the corresponding N-acyclic carbene (NAC)derivatives cis-[PtX2(PPh3)(NAC)] in 61–64% isolated yield. The cis geometry was attributed based on the comparison with known structures. The stability of the complexes in pure DMSO, DMSO/H2O, and DMSO/NaClaq mixtures was evaluated. While pure DMSO, as well as DMSO/H2O, did not affect the nature of either dichloro- or dibromo-compounds, dibromo derivatives were not stable in the presence of chloride ions. Since a high concentration of chloride ions is essential to perform in vitro cell assays, only dichlorocomplexes were tested as cytotoxic agents against HepG2 and human tumor cells. Among the tested complexes, NAC derivatives showed a moderate effect on MSTO-211H. Full article
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14 pages, 2933 KiB  
Article
X-ray Absorption Spectroscopy of Phosphine-Capped Au Clusters
by Shailendra K. Sharma, Bernt Johannessen, Vladimir B. Golovko and Aaron T. Marshall
Inorganics 2023, 11(5), 191; https://doi.org/10.3390/inorganics11050191 - 28 Apr 2023
Cited by 1 | Viewed by 1613
Abstract
The structural determination of ultrasmall clusters remains a challenge due to difficulties in crystallisation. Often the atomically precise clusters undergo structural change under the influence of the environment. X-ray absorption spectroscopy (XAS) can be an attractive tool to study the electronic and geometric [...] Read more.
The structural determination of ultrasmall clusters remains a challenge due to difficulties in crystallisation. Often the atomically precise clusters undergo structural change under the influence of the environment. X-ray absorption spectroscopy (XAS) can be an attractive tool to study the electronic and geometric properties of such clusters deposited onto various supports under in situ conditions. Herein, [Au6(dppp)4](NO3)2, [Au9(PPh3)8](NO3)3, [Au13(dppe)5Cl2]Cl3, and Au101(PPPh3)21Cl5 clusters were studied using XAS. The clusters exhibited distinct features compared to bulk gold. XANES results show a systematic increase in the absorption edge energy and white line intensity, with a decrease in cluster nuclearity. The EXAFS of clusters are sensitive to nuclearity and ligands and were fitted with their known crystal structures. This study advances the understanding of the phosphine-ligated metal clusters relevant to practical applications in catalysis and sensing. Full article
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12 pages, 1089 KiB  
Article
Dibromo–Isonitrile and N-acyclic Carbene Complexes of Platinum(II): Synthesis and Reactivity
by Anna Farasat, Francesca Nerli, Luca Labella, Marco Taddei and Simona Samaritani
Inorganics 2023, 11(4), 137; https://doi.org/10.3390/inorganics11040137 - 23 Mar 2023
Cited by 1 | Viewed by 1256
Abstract
A series of dibromo-N-acyclic (NAC) carbene complexes of platinum(II) were synthesized, starting from trans-[Pt(μ-Br)Br(PPh3)]2 and according to a protocol previously optimized for the preparation of analogous chlorinated compounds. In the first step of the synthesis, the ring opening of [...] Read more.
A series of dibromo-N-acyclic (NAC) carbene complexes of platinum(II) were synthesized, starting from trans-[Pt(μ-Br)Br(PPh3)]2 and according to a protocol previously optimized for the preparation of analogous chlorinated compounds. In the first step of the synthesis, the ring opening of the dinuclear precursor was carried out using suitable isonitrile ligands, while the following step consisted of the addition of N,N-diethylamine to the products obtained in the first step. The two reactions were separately investigated, and attention was given to the differences between brominated and chlorinated systems. Full article
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16 pages, 2605 KiB  
Article
New Phosphonite Ligands with High Steric Demand and Low Basicity: Synthesis, Structural Properties and Cyclometalated Complexes of Pt(II)
by María M. Alcaide, Matteo Pugliesi, Eleuterio Álvarez, Joaquín López-Serrano and Riccardo Peloso
Inorganics 2022, 10(8), 109; https://doi.org/10.3390/inorganics10080109 - 29 Jul 2022
Viewed by 1689
Abstract
Two phosphonite ligands bearing the highly sterically demanding 2,6-bis (2,6-dimethylphenyl)phenyl group (ArXyl2), PArXyl2(OPhNO2)2 and PArXyl2(OPhNO2,Me)2, were prepared from the parent dihalophosphines PArXyl2 [...] Read more.
Two phosphonite ligands bearing the highly sterically demanding 2,6-bis (2,6-dimethylphenyl)phenyl group (ArXyl2), PArXyl2(OPhNO2)2 and PArXyl2(OPhNO2,Me)2, were prepared from the parent dihalophosphines PArXyl2X2 (X = Cl, Br) and the corresponding phenols, 4-nitrophenol and 4-nitro-2,6-dimethylphenol, respectively. DFT methods were used to examine their structural features and to determine three steric descriptors, namely the Tolman cone angle, the percentage of buried volume, and the percentage of the coordination sphere protected by the ligand. A comparison with the related terphenyl phosphines is also provided. Reactions of PArXyl2(OPhNO2)2 and PArXyl2(OPhNO2,Me)2 with several Pt(II) precursors were investigated, revealing a high tendency of both phosphonites to undergo C-H activation processes and generate five- or six-membered cyclometalated structures. The coordination chemistry of the new ligands was explored with isolation, among others, of three carbonyl complexes, 1-3∙CO, and the triphenylphosphine adduct 3∙PPh3. X-ray diffraction methods permitted the determination of the solid-state structures of the mononuclear methyl carbonyl complex 1∙CO, the dinuclear chloride-bridged complex 2 and the doubly cyclometalated complex 3∙SMe2, including the conformations adopted by the ligands upon coordination. All of the new compounds were characterized by multinuclear NMR spectroscopy in solution. Full article
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10 pages, 3027 KiB  
Article
Trigonal Bipyramidal Rhodium(I) Methyl and Phenyl Complexes: Precursors of Oxidative Methyl and Phenyl Radical Generation
by Urs Fischbach, Matthias Vogt, Peter Coburger, Monica Trincado and Hansjörg Grützmacher
Inorganics 2022, 10(3), 28; https://doi.org/10.3390/inorganics10030028 - 24 Feb 2022
Viewed by 2180
Abstract
The new complexes [Rh(Me)(trop3P)] (2) and [Rh(Ph)(trop3P)] (3) (trop = 5H-dibenzo[a,d]cyclohepten-5-yl) were synthesised by addition of organolithium reagents (MeLi and PhLi) to the parent pentacoordinated chloride complex [RhCl(trop3P)]. The [...] Read more.
The new complexes [Rh(Me)(trop3P)] (2) and [Rh(Ph)(trop3P)] (3) (trop = 5H-dibenzo[a,d]cyclohepten-5-yl) were synthesised by addition of organolithium reagents (MeLi and PhLi) to the parent pentacoordinated chloride complex [RhCl(trop3P)]. The compounds have a trigonal bipyramidal structure with olefin-only ligands in the equatorial position and the methyl or phenyl substituent in the axial position. Oxidation of complexes 2 and 3 leads to the liberation of methyl and phenyl radicals, which were indirectly detected by reaction with common spin trapping reagents. Full article
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