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Tomat E, Curtis CJ, Astashkin AV, Conradie J, Ghosh A. Multicenter interactions and ligand field effects in platinum(II) tripyrrindione radicals. Dalton Trans 2023; 52:6559-6568. [PMID: 37185585 DOI: 10.1039/d3dt00894k] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The tripyrrin-1,14-dione biopyrrin, which shares the scaffold of several naturally occurring heme metabolites, is a redox-active platform for metal coordination. We report the synthesis of square planar platinum(II) tripyrrindiones, in which the biopyrrin binds as a tridentate radical and the fourth coordination position is occupied by either aqua or tert-butyl isocyanide ligands. These complexes are stable through chromatographic purification and exposure to air. Electron paramagnetic resonance (EPR) data and density functional theory (DFT) analysis confirm that the spin density is located predominantly on the tripyrrindione ligand. Pancake bonding in solution between the Pt(II) tripyrrindione radicals leads to the formation of diamagnetic π dimers at low temperatures. The identity of the monodentate ligand (i.e., aqua vs. isocyanide) affects both the thermodynamic parameters of dimerization and the tripyrrindione-based redox processes in these complexes. Isolation and structural characterization of the oxidized complexes revealed stacking of the diamagnetic tripyrrindiones in the solid state as well as a metallophilic Pt(II)-Pt(II) contact in the case of the aqua complex. Overall, the properties of Pt(II) tripyrrindiones, including redox potentials and intermolecular interactions in solution and in the solid state, are modulated through easily accessible changes in the redox state of the biopyrrin ligand or the nature of the monodentate ligand.
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Affiliation(s)
- Elisa Tomat
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721-0041, USA.
| | - Clayton J Curtis
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721-0041, USA.
| | - Andrei V Astashkin
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721-0041, USA.
| | - Jeanet Conradie
- Department of Chemistry, University of the Free State, Bloemfontein 9300, Republic of South Africa
- Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway.
| | - Abhik Ghosh
- Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway.
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Maidich L, Pilo MI, Rourke JP, Clarkson GJ, Canu P, Stoccoro S, Zucca A. Classical vs. Non-Classical Cyclometalated Pt(II) Complexes. Molecules 2022; 27:7249. [PMID: 36364075 PMCID: PMC9654721 DOI: 10.3390/molecules27217249] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 10/18/2022] [Accepted: 10/19/2022] [Indexed: 09/10/2023] Open
Abstract
Rollover cyclometalated complexes constitute a family of derivatives which differ from classical cyclometalated species in certain aspects. Various potential application fields have been developed for both classes of compounds, which have both similarities and differences. In order to uncover the relationships and distinctions between these two families of compounds, four Pt(II) cyclometalated complexes derived from 2-phenylpyridine (ppy) and 2,2'-bipyridine (bpy), assumed as prototypical ligands, were compared. For this study, an electron rich isostructural and isoelectronic pair of compounds, [Pt(N^C)Me(PPh3)], and an electron-poorer compound, [Pt(N^C)Cl(PPh3)] were chosen (N^C = ppy or bpy). DFT calculations, cyclic voltammetry, and UV-Vis spectra also helped to shed light into these species. Due to the presence of the more electronegative nitrogen in place of a C-H group, the rollover bpy-H ligand becomes a slightly weaker donor than the classical ppy-H ligand, and hence, generates (slightly) more stable cyclometalated complexes, lower energy frontier molecular orbitals, and electron-poorer platinum centers. On the whole, it was revealed that classical and rollover complexes have overall structural similarity, which contrasts to their somewhat different chemical behavior.
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Affiliation(s)
- Luca Maidich
- Department of Chemical, Physical, Mathematical and Natural Sciences, University of Sassari, Via Vienna 2, 07100 Sassari, Italy
| | - Maria I. Pilo
- Department of Chemical, Physical, Mathematical and Natural Sciences, University of Sassari, Via Vienna 2, 07100 Sassari, Italy
| | - Jonathan P. Rourke
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
| | - Guy J. Clarkson
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Patrizia Canu
- Department of Chemical, Physical, Mathematical and Natural Sciences, University of Sassari, Via Vienna 2, 07100 Sassari, Italy
| | - Sergio Stoccoro
- Department of Chemical, Physical, Mathematical and Natural Sciences, University of Sassari, Via Vienna 2, 07100 Sassari, Italy
| | - Antonio Zucca
- Department of Chemical, Physical, Mathematical and Natural Sciences, University of Sassari, Via Vienna 2, 07100 Sassari, Italy
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Zucca A, Pilo MI. Rollover Cyclometalation as a Valuable Tool for Regioselective C-H Bond Activation and Functionalization. Molecules 2021; 26:E328. [PMID: 33435257 PMCID: PMC7827749 DOI: 10.3390/molecules26020328] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/03/2021] [Accepted: 01/04/2021] [Indexed: 01/31/2023] Open
Abstract
Rollover cyclometalation constitutes a particular case of cyclometallation reaction. This reaction occurs when a chelated heterocyclic ligand loses its bidentate coordination mode and undergoes an internal rotation, after which a remote C-H bond is regioselectively activated, affording an uncommon cyclometalated complex, called "rollover cyclometalated complex". The key of the process is the internal rotation of the ligand, which occurs before the C-H bond activation and releases from coordination a donor atom. The new "rollover" ligand has peculiar properties, being a ligand with multiple personalities, no more a spectator in the reactivity of the complex. The main reason of this peculiarity is the presence of an uncoordinated donor atom (the one initially involved in the chelation), able to promote a series of reactions not available for classic cyclometalated complexes. The rollover reaction is highly regioselective, because the activated C-H bond is usually in a symmetric position with respect to the donor atom which detaches from the metal stating the rollover process. Due to this novel behavior, a series of potential applications have appeared in the literature, in fields such as catalysis, organic synthesis, and advanced materials.
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Affiliation(s)
- Antonio Zucca
- Department of Chemistry and Pharmacy, University of Sassari, via Vienna 2, 07100 Sassari, Italy;
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Stoccoro S, Maidich L, Ruiu T, Cinellu MA, Clarkson GJ, Zucca A. Chiral cyclometalation of 6-(1-phenylbenzyl)-2,2'-bipyridine. Dalton Trans 2015; 44:18001-11. [PMID: 26407175 DOI: 10.1039/c5dt02483h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new bipyridine ligand, 6-(1-phenylbenzyl)-2,2'-bipyridine, has been prepared by a multistep synthesis starting from the corresponding substituted pyridine. The coordinating properties of the new ligand have been tested with two d(8) metal ions, Pt(ii) and Pd(ii), to give the cyclometalated complexes [Pt(N,N,C)Cl] and [Pd(N,N,C)Cl], where N,N,C is a terdentate deprotonated bipyridine containing a new stereogenic carbon atom directly generated by C-H bond activation. The single-crystal of the platinum complex has been solved by X-ray diffraction. DFT calculations confirm the presence of a PtH interaction that stabilizes one of the two possible conformers by 14.7 kJ mol(-1) for Pt and 12.9 kJ mol(-1) for Pd. The energy barrier to pass from one conformer to the other is 25.4 and 23.8 kJ mol(-1) respectively. Under different reaction conditions, regioselective activation of a pyridine C-H bond gave the less common cyclometalated rollover complex [Pt(L-H)Me(DMSO)], which was isolated and characterised.
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Affiliation(s)
- Sergio Stoccoro
- Dipartimento di Chimica e Farmacia, Università degli Studi di Sassari, via Vienna 2, 07100 Sassari, Italy.
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Raoof F, Boostanizadeh M, Esmaeilbeig AR, Nabavizadeh SM, Aghakhanpour RB, Ghiassi KB, Olmstead MM, Balch AL. Reactivity comparison of five-and six-membered cyclometalated platinum(ii) complexes in oxidative addition reactions. RSC Adv 2015. [DOI: 10.1039/c5ra17421j] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
A six-membered cyclometalated complex [PtMe(bzpy)(PPh3)] (bzpy = 2-benzylpyridinate) undergoes oxidative addition with methyl iodide to give [PtMe2I(bzpy)(PPh3)]. The ring size of the chelating unit has a significant impact on the rate of the reaction.
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Affiliation(s)
- Fatemeh Raoof
- Department of Chemistry
- College of Sciences
- Shiraz University
- Shiraz 71467-13565
- Iran
| | - Maryam Boostanizadeh
- Department of Chemistry
- College of Sciences
- Shiraz University
- Shiraz 71467-13565
- Iran
| | - Ahmad R. Esmaeilbeig
- Department of Chemistry
- College of Sciences
- Shiraz University
- Shiraz 71467-13565
- Iran
| | | | | | | | | | - Alan L. Balch
- Department of Chemistry
- University of California
- Davis
- USA
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Zucca A, Maidich L, Canu L, Petretto GL, Stoccoro S, Cinellu MA, Clarkson GJ, Rourke JP. Rollover-assisted C(sp2)-C(sp3) bond formation. Chemistry 2014; 20:5501-10. [PMID: 24682987 DOI: 10.1002/chem.201304257] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 01/17/2014] [Indexed: 11/12/2022]
Abstract
Rollover cyclometalation involves bidentate heterocyclic donors, unusually acting as cyclometalated ligands. The resulting products, possessing a free donor atom, react differently from the classical cyclometalated complexes. Taking advantage of a "rollover"/"retro-rollover" reaction sequence, a succession of oxidative addition and reductive elimination in a series of platinum(II) complexes [Pt(N,C)(Me)(PR3)] resulted in a rare C(sp(2))-C(sp(3)) bond formation to give the bidentate nitrogen ligands 3-methyl-2,2'-bipyridine, 3,6-dimethyl-2,2'-bipyridine, and 3-methyl-2-(2'-pyridyl)-quinoline, which were isolated and characterized. The nature of the phosphane PR3 is essential to the outcome of the reaction. This route constitutes a new method for the activation and functionalization of C-H bond in the C(3) position of bidentate heterocyclic compounds, a position usually difficult to functionalize.
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Affiliation(s)
- Antonio Zucca
- Dipartimento di Chimica e Farmacia, Università degli Studi di Sassari, Via Vienna 2, 07100 Sassari (Italy).
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Carroll J, Gagnier JP, Garner AW, Moots JG, Pike RD, Li Y, Huo S. Reaction of N-Isopropyl-N-phenyl-2,2′-bipyridin-6-amine with K2PtCl4: Selective C–H Bond Activation, C–N Bond Cleavage, and Selective Acylation. Organometallics 2013. [DOI: 10.1021/om400540y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Jeffrey Carroll
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Joshua P. Gagnier
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Alexander W. Garner
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Justin G. Moots
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Robert D. Pike
- Department of Chemistry, College of William and Mary, Williamsburg, Virginia 23185, United States
| | - Yumin Li
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Shouquan Huo
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
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Maidich L, Zuri G, Stoccoro S, Cinellu MA, Masia M, Zucca A. Mesoionic Complexes of Platinum(II) Derived from “Rollover” Cyclometalation: A Delicate Balance between Pt–C(sp3) and Pt–C(sp2) Bond Cleavage as a Result of Different Reaction Conditions. Organometallics 2013. [DOI: 10.1021/om300824d] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Luca Maidich
- Dipartimento di Chimica
e Farmacia, Università di Sassari, via Vienna 2, 07100 Sassari, Italy
| | - Giuseppina Zuri
- Dipartimento di Chimica
e Farmacia, Università di Sassari, via Vienna 2, 07100 Sassari, Italy
| | - Sergio Stoccoro
- Dipartimento di Chimica
e Farmacia, Università di Sassari, via Vienna 2, 07100 Sassari, Italy
| | - Maria Agostina Cinellu
- Dipartimento di Chimica
e Farmacia, Università di Sassari, via Vienna 2, 07100 Sassari, Italy
| | - Marco Masia
- Dipartimento di Chimica
e Farmacia, Università di Sassari, via Vienna 2, 07100 Sassari, Italy
| | - Antonio Zucca
- Dipartimento di Chimica
e Farmacia, Università di Sassari, via Vienna 2, 07100 Sassari, Italy
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Zucca A, Cordeschi D, Stoccoro S, Cinellu MA, Minghetti G, Chelucci G, Manassero M. Platinum(II)-Cyclometalated “Roll-over” Complexes with a Chiral Pinene-Derived 2,2′-Bipyridine. Organometallics 2011. [DOI: 10.1021/om200172h] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Plutino MR, Fenech L, Stoccoro S, Rizzato S, Castellano C, Albinati A. Dynamic NMR Study of Ethene Exchange in Cationic CNN-Type Platinum(II) Complexes. Inorg Chem 2009; 49:407-18. [DOI: 10.1021/ic901078u] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- M. Rosaria Plutino
- Istituto per lo Studio dei Materiali Nanostrutturati, ISMN−CNR, Unità di Messina-Sezione di Palermo, Messina, Italy
| | - Lucia Fenech
- Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Salita Sperone 31, 98166 Vill. S. Agata, Messina, Italy
| | - Sergio Stoccoro
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, 07100, Sassari, Italy
| | - Silvia Rizzato
- Dipartimento di Chimica Strutturale e Facoltà di Farmacia, via Venezian 21, Università di Milano, 20133, Milano, Italy
| | - Carlo Castellano
- Dipartimento di Chimica Strutturale e Facoltà di Farmacia, via Venezian 21, Università di Milano, 20133, Milano, Italy
| | - Alberto Albinati
- Dipartimento di Chimica Strutturale e Facoltà di Farmacia, via Venezian 21, Università di Milano, 20133, Milano, Italy
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N^N^C platinum(II) and palladium(II) cyclometallates of 6,6′-diphenyl-2,2′-bipyridine, L: Crystal and molecular structure of [Pd(L–H)Cl]. J Organomet Chem 2009. [DOI: 10.1016/j.jorganchem.2009.07.034] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Fedi S, Zanello P, Laschi F, Ceriotti A, El Afefey S. A joint electrochemical/spectroelectrochemical inspection (and re-inspection) of high-nuclearity platinum carbonyl clusters. J Solid State Electrochem 2009. [DOI: 10.1007/s10008-009-0880-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Zucca A, Petretto GL, Stoccoro S, Cinellu MA, Manassero M, Manassero C, Minghetti G. Cyclometalation of 2,2′-Bipyridine. Mono- and Dinuclear C,N Platinum(II) Derivatives. Organometallics 2009. [DOI: 10.1021/om801033g] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Antonio Zucca
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, I-07100 Sassari, Italy, and Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Università di Milano, Centro CNR, Via Venezian 21, I-20133 Milano, Italy
| | - Giacomo Luigi Petretto
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, I-07100 Sassari, Italy, and Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Università di Milano, Centro CNR, Via Venezian 21, I-20133 Milano, Italy
| | - Sergio Stoccoro
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, I-07100 Sassari, Italy, and Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Università di Milano, Centro CNR, Via Venezian 21, I-20133 Milano, Italy
| | - Maria Agostina Cinellu
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, I-07100 Sassari, Italy, and Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Università di Milano, Centro CNR, Via Venezian 21, I-20133 Milano, Italy
| | - Mario Manassero
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, I-07100 Sassari, Italy, and Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Università di Milano, Centro CNR, Via Venezian 21, I-20133 Milano, Italy
| | - Carlo Manassero
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, I-07100 Sassari, Italy, and Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Università di Milano, Centro CNR, Via Venezian 21, I-20133 Milano, Italy
| | - Giovanni Minghetti
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, I-07100 Sassari, Italy, and Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Università di Milano, Centro CNR, Via Venezian 21, I-20133 Milano, Italy
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Minghetti G, Stoccoro S, Cinellu MA, Petretto GL, Zucca A. N,C “Rollover” Cyclometalated Platinum(II) Hydrides: Mono- and Polynuclear Derivatives. Organometallics 2008. [DOI: 10.1021/om800027g] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Giovanni Minghetti
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, 07100 Sassari, Italy
| | - Sergio Stoccoro
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, 07100 Sassari, Italy
| | | | | | - Antonio Zucca
- Dipartimento di Chimica, Università di Sassari, via Vienna 2, 07100 Sassari, Italy
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Zucca A, Stoccoro S, Cinellu MA, Petretto GL, Minghetti G. Cyclometalated Platinum(II) Hydrides with Nitrogen Ligands. Organometallics 2007. [DOI: 10.1021/om7005276] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Antonio Zucca
- Università degli Studi di Sassari, Dipartimento di Chimica, via Vienna 2, 07100 Sassari, Italy
| | - Sergio Stoccoro
- Università degli Studi di Sassari, Dipartimento di Chimica, via Vienna 2, 07100 Sassari, Italy
| | - Maria Agostina Cinellu
- Università degli Studi di Sassari, Dipartimento di Chimica, via Vienna 2, 07100 Sassari, Italy
| | - Giacomo Luigi Petretto
- Università degli Studi di Sassari, Dipartimento di Chimica, via Vienna 2, 07100 Sassari, Italy
| | - Giovanni Minghetti
- Università degli Studi di Sassari, Dipartimento di Chimica, via Vienna 2, 07100 Sassari, Italy
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Stoccoro S, Zucca A, Petretto GL, Cinellu MA, Minghetti G, Manassero M. Dinuclear platinum(II) complexes with bridging twofold deprotonated 2,2′:6′,2″-terpyridine. New molecules with a 3,5-diplatinated-pyridyl inner core: [Pt2(terpy-2H)(Me)2(L)2], [Pt2(terpy-2H)(X)2(L)2] and [Pt2(terpy-2H)(H)2(L)2] (L=neutral ligand; X=halide) – Crystal and molecular structure of [Pt2(terpy-2H)(Cl)2(PPh3)2]. J Organomet Chem 2006. [DOI: 10.1016/j.jorganchem.2006.06.024] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Zucca A, Petretto GL, Stoccoro S, Cinellu MA, Minghetti G, Manassero M, Manassero C, Male L, Albinati A. Dinuclear C,N,C Cyclometalated Platinum Derivatives with Bridging Delocalized Ligands. Fourfold Deprotonation of 6,6‘-Diphenyl-2,2‘-bipyridine, H4L, Promoted by “Pt(R)2” Fragments (R = Me, Ph). Crystal Structures of [Pt2(L)(3,5-Me2py)2] and {Pt2(L)(dppe)}2 (dppe = 1,2-Bis(diphenylphosphino)ethane). X-ray Powder Diffraction of [Pt2(L)(CO)2]. Organometallics 2006. [DOI: 10.1021/om051075k] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Zucca A, Cinellu M, Minghetti G, Stoccoro S, Manassero M. Dinuclear, Tricyclometallated Platinum(II) Derivatives ? Substitution Reactions and Reactivity of the Platinum?Carbon Bonds. Eur J Inorg Chem 2004. [DOI: 10.1002/ejic.200400371] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Sanna G, Pilo MI, Spano N, Minghetti G, Cinellu MA, Zucca A, Seeber R. Electrochemical behaviour of cyclometallated gold(III) complexes. Evidence of transcyclometallation in the fate of electroreduced species. J Organomet Chem 2001. [DOI: 10.1016/s0022-328x(00)00822-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Sanna G, Pilo MI, Minghetti G, Cinellu MA, Spano N, Seeber R. Electrochemical properties of gold(III) complexes with 2,2′-bipyridine and oxygen ligands. Inorganica Chim Acta 2000. [DOI: 10.1016/s0020-1693(00)00264-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Romeo R, Plutino MR, Monsù Scolaro L, Stoccoro S, Minghetti G. Role of cyclometalation in controlling the rates of ligand substitution at platinum(II) complexes. Inorg Chem 2000; 39:4749-55. [PMID: 11196950 DOI: 10.1021/ic0004479] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The rates of chloride for triphenylphosphine substitution have been measured in dichloromethane for a series of cyclometalated [Pt(N-N-C)Cl] complexes containing a number of terdentate N-N-C anionic ligands, derived from deprotonated alkyl-, phenyl-, and benzyl-6-substituted 2,2'-bipyridines. These rates have been compared with those of the corresponding [Pt(N-N)(C)Cl] (N-N = 2,2'-bipyridine; C = CH3 or C6H5) complexes having the same set of donor atoms but less constrained arrangements of the ligands. The reactions of the cyclometalated compounds occur as a single-stage conversion from the substrate to the ionic pair [Pt(N-N-C)(PPh3)]Cl products. There is no evidence by 1H and 31P(1H) NMR spectroscopy for the formation of other Pt(II) species or of concurrent ring-opening processes. In contrast, in the monoalkyl- or monoaryl-2,2'-bipyridine complexes, chloride substitution is followed by subsequent slower processes which involve the detachment of one arm of the chelated 2,2'-bipyridine, fast cis to trans isomerization of the cis-[Pt(PPh3)2(eta 1-bipy)(R)]+ transient intermediate, and, eventually, the release of free bipy, yielding trans-[Pt(PPh3)2(R)Cl] (R = Me or Ph). All reactions are first-order with respect to complex and phosphine concentration, obeying the simple rate law kobsd = k2[PPh3]. The values of the second-order rate constant k2 do not seem particularly sensitive to the nature of the bonded organic moiety (alkyl or aryl), to its structure (cyclometalated or not), to the size of the ring, or to the number of alkyl substituents on it. The effects are those foreseen on the basis of an associative mode of activation. The only exception to this pattern of behavior is constituted by the complex [Pt(bipy phi-H)Cl] (bipy phi = 6-phenyl-2,2'-bipyridine), which features a significant rate enhancement with respect to the analogue [Pt(bipy)(Ph)Cl] complex. The results of this work, together with those of a previous paper, suggest that there is not a specific role of cyclometalation in controlling the reactivity, unless an in-plane aryl ring becomes part of the pi-acceptor system of the chelated 2,2-bipyridine, behaving as a cyclometalated analogue of the nitrogen terdentate 2,2':6',2"-terpyridine.
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Affiliation(s)
- R Romeo
- Dipartimento di Chimica Inorganica, Fisica e Istituto di Chimica e Tecnologia dei Prodotti Naturali (ICTPN-CNR), Università di Messina, Salita Sperone 31, Vill. S. Agata, 98166 Messina, Italy.
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