Synthesis and Characterization of Pt(II) Complexes with Pyridyl Ligands: Elongated Octahedral Ion Pairs and Other Factors Influencing<sup>1</sup>H NMR Spectra

Lewis, Nita A.; Pakhomova, Svetlana; Marzilli, Patricia A.; Marzillï, Luigi G.

doi:10.1021/acs.inorgchem.7b01294

Cited by 9 publications

(19 citation statements)

References 51 publications

(135 reference statements)

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“…For both coordination complexes trans - and cis - 4 , the platinum displays a nearly perfect square-planar geometry, which is similar to the crystal structures of cis - and trans -dichlorobispyridine platinum complexes reported previously . Although the two organic ligands in trans - 4 are placed symmetrically with Pt as the inversion center, the cis - 4 has two coordinating ligands arranged unsymmetrically, which is obviously due to the steric effect.…”

Section: Resultsmentioning

confidence: 85%

Isomerization-Induced Multiple Reaction Pathways in Platinum-Catalyzed C–H Acylation Reaction of 2-Aryloxypyridines

et al. 2021

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In Pt-catalyzed C–H acylation of 2-(2-methylphenoxy)pyridine (L 1 ) with ethyl chlorooxoacetate to produce ethyl 2-(3-methyl-2-(pyridin-2-yloxy))phenyl-2-oxoacetate (L 2 ), possible reaction steps involved in the catalytic cycle have been investigated, which include the ligand exchange of precatalysts cis- and trans-Pt(PhCN)2Cl2 with L 1 , the intramolecular C–H activation (cyclometalation) of cis- and trans-Pt(L 1 )2Cl2 (1), and the acylation of the trans-cyclometalated platinum complex (trans-2) formed from the C–H activation reaction. The cis coordination compounds including the intermediate platinum complexes have shown much higher reactivity toward the ligand exchange and the C–H activation than their trans isomers. Consequently, the cis isomers exhibit higher catalytic activity in the C–H acylation reaction. Although the C–H activation of cis- and trans-Pt(L 1 )2Cl2 produces trans-2, the cis isomer (cis-2) is very likely formed in the C–H activation of cis-Pt(L 1 )2Cl2 but undergoes isomerization to the more stable trans-2. The results suggest that the fast reaction pathway via all cis-platinum complexes may be responsible for the efficient catalytic reaction, but isomerization of cis-2 to trans-2 could be highly competitive. The acylation of the trans-cycloplatinated complex produces both cis- and trans-platinum complexes Pt(L 1 )(L 2 )Cl2. The regaining of the cis-platinum complex revives the catalytic cycle.

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Section: Resultsmentioning

confidence: 85%

Isomerization-Induced Multiple Reaction Pathways in Platinum-Catalyzed C–H Acylation Reaction of 2-Aryloxypyridines

et al. 2021

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“…This preference for the trans configuration mimics that known for various Pt(II) analogues. 11 The use of PdCl 2 or [Pd(DMSO) 2 Cl 2 ] (DMSO = dimethyl sulfoxide) as reactants for the formation of [Pd L 4 ] 2+ cations ( 1c – 12c ) was efficient but required the elimination of chloride from the reaction mixtures by the addition of AgNO 3 . The ease of formation of the [Pd L 4 ] 2+ cations appeared to increase with the basicity of the ligand, and this may explain why a pure species 6b could not be isolated with the most strongly basic unit L6 .…”

Section: Resultsmentioning

confidence: 99%

“…9 Where direct complexation equilibrium measurements of the Lewis basicity of a ligand are unavailable, the Brønsted basicity, measured as pK a values, usually rather readily obtained for pyridine derivatives, has been widely applied as a measure of the effect of any substituent on pyridine donor behavior. 10 In a recent study of Pt(II) complexes of 4-substituted pyridines having some parallels with the present study of Pd(II) species, 11 it was found that the 1 H NMR chemical shifts of the 2/6 protons showed a same linear dependence on the pK a for the coordinated as well as free ligands, consistent with protonation being a useful guide to coordination behavior. Pd(II) complexes with pyridine derivatives have been used as efficient catalysts in reactions such as the carbonylation of nitro compounds, 12 reduction of nitro compounds to amines, 13 or carbonylation of aniline derivatives by CO/O 2 .…”

Section: ■ Introductionmentioning

confidence: 99%

“…A comparison of the various trans-[PdL 2 (NO 3 ) 2 ] (1b−12b) and trans-[PdL 2 Cl 2 ] (1a−12a) pairs shows that the H 1 chemical shifts are sensitive to the nature of the adjacent donor atom, and this is presumably a contributor to the very large downfield shifts (∼0.5−1 ppm relative to those of the free ligands) for the H 1 proton signals of complexes 1c−12c, although the dominant effect here may be that of ion pairing involving C−H 1 •••ONO 2 bonding, as proposed to explain similar observations on Pt(II) analogues. 11 Again, as observed for Pt(II), the H 1 chemical shifts (Table 1) show a close-to-linear dependence on the pK a values of the protonated ligands (Figure 2), indicating that the substituent effects remain operative along with any effects of Pd(II) coordination.…”

Section: ■ Introductionmentioning

confidence: 99%

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Pd(II) Complexes with Pyridine Ligands: Substituent Effects on the NMR Data, Crystal Structures, and Catalytic Activity

et al. 2022

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A wide range of functionalized pyridine ligands have been employed to synthesize a variety of Pd(II) complexes of the general formulas [Pd L 4 ](NO 3 ) 2 and [Pd L 2 Y 2 ], where L = 4-X-py and Y = Cl – or NO 3 – . Their structures have been unambiguously established via analytical and spectroscopic methods in solution (NMR spectroscopy and mass spectrometry) as well as in the solid state (X-ray diffraction). This in-depth characterization has shown that the functionalization of ligand molecules with groups of either electron-withdrawing or -donating nature (EWG and EDG) results in significant changes in the physicochemical properties of the desired coordination compounds. Downfield shifts of signals in the 1 H NMR spectra were observed upon coordination within and across the complex families, clearly indicating the relationship between NMR chemical shifts and the ligand basicity as estimated from p K a values. A detailed crystallographic study has revealed the operation of a variety of weak interactions, which may be factors explaining aspects of the solution chemistry of the complexes. The Pd(II) complexes have been found to be efficient and versatile precatalysts in Suzuki–Miyaura and Heck cross-coupling reactions within a scope of structurally distinct substrates, and factors have been identified that have contributed to efficiency improvement in both processes.

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“…All of the Pt−N bonds have lengths (Table 1) falling in the range typically reported for Pt−N(sp 2 ) bonds (1.99−2.08 Å). 21,56 The bidentate coordination mode in the Pt(N(SO 2 R)3,3′,5,5′-Me 4 dpa)Cl 2 complexes [R = Me (5), R = Tol (6); Figure 5] creates a relatively large and uncommon eight-membered chelate ring.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Linear Bidentate Ligands (L) with Two Terminal Pyridyl N-Donor Groups Forming Pt(II)LCl₂ Complexes with Rare Eight-Membered Chelate Rings

et al. 2018

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NMR and X-ray diffraction studies were conducted on Pt(II)LCl2 complexes prepared with the new N-donor ligands N(SO2R)Me n dpa (R = Me, Tol; n = 2, 4). These ligands differ from N(H)dpa (di-2-picolylamine) in having the central N within a tertiary sulfonamide group instead of a secondary amine group and having Me groups at the 6,6′-positions (n = 2) or 3,3′,5,5′-positions (n = 4) of the pyridyl rings. The N(SO2R)3,3′,5,5′-Me4dpa ligands are coordinated in a bidentate fashion in Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes, forming a rare eight-membered chelate ring. The sulfonamide N atom did not bind to Pt(II), consistent with indications in the literature that tertiary sulfonamides are unlikely to anchor two meridionally coordinated five-membered chelate rings in solutions of coordinating solvents. The N(SO2R)6,6′-Me2dpa ligands coordinate in a monodentate fashion to form the binuclear complexes [trans-Pt(DMSO)Cl2]2(N(SO2R)6,6′-Me2dpa). The monodentate instead of bidentate N(SO2R)6,6′-Me2dpa coordination is attributed to 6,6′-Me steric bulk. These binuclear complexes are indefinitely stable in DMF-d 7, but in DMSO-d 6 the N(SO2R)6,6′-Me2dpa ligands dissociate completely. In DMSO-d 6, the bidentate ligands in Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes also dissociate, but incompletely; these complexes provide rare examples of association–dissociation equilibria of N,N bidentate ligands in Pt(II) chemistry. Like typical cis-PtLCl2 complexes, the Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes undergo monosolvolysis in DMSO-d 6 to form the [Pt(N(SO2R)3,3′,5,5′-Me4dpa)(DMSO-d 6)Cl]+ cations. However, unlike typical cis-PtLCl2 complexes, the Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes surprisingly do not react readily with the excellent N-donor bioligand guanosine. A comparison of the structural features of over 50 known relevant Pt(II) complexes having smaller chelate rings with those of the very few relevant Pt(II) complexes having eight-membered chelate rings indicates that the pyridyl rings in Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes are well positioned to form strong Pt–N bonds. Therefore, the dissociation of the bidentate ligand and the poor biomolecule reactivity of the Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes arise from steric consequences imposed by the −CH2–N(SO2R)–CH2– chain in the eight-membered chelate ring.

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Synthesis and Characterization of Pt(II) Complexes with Pyridyl Ligands: Elongated Octahedral Ion Pairs and Other Factors Influencing¹H NMR Spectra

Cited by 9 publications

References 51 publications

Isomerization-Induced Multiple Reaction Pathways in Platinum-Catalyzed C–H Acylation Reaction of 2-Aryloxypyridines

Isomerization-Induced Multiple Reaction Pathways in Platinum-Catalyzed C–H Acylation Reaction of 2-Aryloxypyridines

Pd(II) Complexes with Pyridine Ligands: Substituent Effects on the NMR Data, Crystal Structures, and Catalytic Activity

Linear Bidentate Ligands (L) with Two Terminal Pyridyl N-Donor Groups Forming Pt(II)LCl₂ Complexes with Rare Eight-Membered Chelate Rings

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Synthesis and Characterization of Pt(II) Complexes with Pyridyl Ligands: Elongated Octahedral Ion Pairs and Other Factors Influencing1H NMR Spectra

Cited by 9 publications

References 51 publications

Isomerization-Induced Multiple Reaction Pathways in Platinum-Catalyzed C–H Acylation Reaction of 2-Aryloxypyridines

Isomerization-Induced Multiple Reaction Pathways in Platinum-Catalyzed C–H Acylation Reaction of 2-Aryloxypyridines

Pd(II) Complexes with Pyridine Ligands: Substituent Effects on the NMR Data, Crystal Structures, and Catalytic Activity

Linear Bidentate Ligands (L) with Two Terminal Pyridyl N-Donor Groups Forming Pt(II)LCl2 Complexes with Rare Eight-Membered Chelate Rings

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Synthesis and Characterization of Pt(II) Complexes with Pyridyl Ligands: Elongated Octahedral Ion Pairs and Other Factors Influencing¹H NMR Spectra

Linear Bidentate Ligands (L) with Two Terminal Pyridyl N-Donor Groups Forming Pt(II)LCl₂ Complexes with Rare Eight-Membered Chelate Rings