Über die Darstellung und die Kristallstruktur der Komplexverbindungen Ni(py)4F2 · 2H2O und Cu(py)4F2 · 1,33 HF · 2H2O

Holzbock, J.; Sawodny, W.; Walz, L.

doi:10.1524/zkri.1997.212.2.115

Cited by 14 publications

(5 citation statements)

References 6 publications

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“…The ratio g ∥ / A ∥ is small (134 cm), demonstrating the absence of significant dihedral angle distortion in the xy -plane. In addition, the optical and EPR data for 3 correlate very well with crystallographically characterized tetrakispyridine complexes of Cu(II). − Based on the above chemical and spectroscopic evidence, the structures of 2 and 3 are best described as four-coordinate tetrahedral and six-coordinate tetragonal Cu(I) and Cu(II) complexes, respectively.…”

Section: Resultsmentioning

confidence: 59%

“…The 1 H and 13 C NMR spectra of these complexes reveal two equivalent enediyne or pyridyl ligands, indicating a symmetric copper center in solution. In contrast, Cu(II) complexes with an N 4 ligand field can adopt coordination numbers from 4 to 6, the latter via solvent or counterion ligation, and have geometries ranging from square planar , to cis , or trans − distorted octahedral. A combination of electronic absorption spectroscopy in the ligand field region and EPR have proven very effective for characterizing the structures of Cu(II) centers in both inorganic complexes − and protein active sites. , Typically, four-coordinate square planar complexes exhibit three optical absorption features ( 2 B 1g → 2 A 1g , 2 B 1g → 2 B 2g , 2 B 1g → 2 E g in D 4 h ) between 17 000 and 20 000 cm -1 , whereas for six-coordinate tetragonal structures this envelope is shifted to lower energy (11 000−16 000 cm -1 ).…”

Section: Resultsmentioning

confidence: 99%

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Metalloenediynes: Ligand Field Control of Thermal Bergman Cyclization Reactions

2000

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We report the preparation and thermal reactivities of unique Cu(I) and Cu(II) metalloenediyne complexes of the flexible 1,8-bis(pyridine-3-oxy)oct-4-ene-2,6-diyne ligand (bpod, 1). The thermal reactivities of these metalloenediynes are intimately modulated by metal oxidation state. Using differential scanning calorimetry (DSC), we demonstrate that the [Cu(bpod) 2 ] + complex (2) undergoes Bergman cyclization at 203 °C, whereas the Cu(II) analogue ( 3) is substantially more reactive and cyclizes at 121 °C. Similar results are also observed for mixed ligand [Cu(bpod)(pyridine) 2 ] +/2+ analogues 4 (194 °C) and 5 (116 °C), suggesting that both complexes of a given oxidation state have comparable structures. The Cu(bpod)Cl 2 compound (6) exhibits a cyclization temperature (152 °C) midway between the those of Cu(I) and Cu(II) complexes, which can be explained by the propensity for cis-CuN 2 Cl 2 structures to exhibit dihedral angle distortion. The oxidationstate-dependent thermal reactivity is unprecedented and reflects the influence of the ligand field geometry on the barrier to enediyne cyclization. On the basis of X-ray structures of Cu(pyridine) 4 + complexes, 2 and 4 are proposed to be tetrahedral. In contrast, the electronic absorption spectra of 3 and 5 each show a broad envelope that can be Gaussian resolved into three ligand field transitions characteristic of a Cu(II) center in a tetragonaloctahedral environment. This structural assignment is confirmed by the EPR spin Hamiltonian parameters (g | /A | (cm) ) 134 (3), 138 ( 5)) and is consistent with crystallographically characterized Cu(pyridine) 4 X 2 structures. Molecular mechanics calculations have independently derived comparable tetrahedral and tetragonal structures for 2 and 3, respectively, and determined the average alkyne termini separation to be 〈a〉 ) 4.0 Å for 2 and 3.6 Å for 3. Thus, the tetrahedral geometries of the copper centers in 2 and 4 increase the distance between alkyne termini relative to the tetragonal Cu(II) geometries of 3 and 5, and are therefore responsible for the increase in the thermal cyclization temperatures. The DSC and spectroscopic data for 6 support these conclusions, as the latter suggests a distorted four-coordinate structure in the solid state, and a six-coordinate geometry in solution, which gives rise to an intermediate Bergman cyclization temperature. Overall, our results emphasize the utility of newly emerging metalloenediyne complexes for controlling thermal Bergman cyclization reactions and provide insights into designing novel, pharmacologically useful metalloenediyne compounds.

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Section: Resultsmentioning

confidence: 59%

Section: Resultsmentioning

confidence: 99%

Metalloenediynes: Ligand Field Control of Thermal Bergman Cyclization Reactions

2000

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“…(3) Complex 6 is a new member of the small family of transition metal complexes containing bifluoride as a ligand. ,,,,,,,− All geometry parameters found for 6 and the analogous fluoride 3 are similar, except the Rh−F bond in 6 is elongated by ca. 0.04 Å, as a result of HF hydrogen bonding.…”

Section: Resultsmentioning

confidence: 99%

The F/Ph Rearrangement Reaction of [(Ph₃P)₃RhF], the Fluoride Congener of Wilkinson's Catalyst

et al. 2005

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The fluoride congener of Wilkinson's catalyst, [(Ph(3)P)(3)RhF] (1), has been synthesized and fully characterized. Unlike Wilkinson's catalyst, 1 easily activates the inert C-Cl bond of ArCl (Ar = Ph, p-tolyl) under mild conditions (3 h at 80 degrees C) to produce trans-[(Ph(3)P)(2)Rh(Ph(2)PF)(Cl)] (2) and ArPh as a result of C-Cl, Rh-F, and P-C bond cleavage and C-C, Rh-Cl, and P-F bond formation. In benzene (2-3 h at 80 degrees C), 1 decomposes to a 1:1 mixture of trans-[(Ph(3)P)(2)Rh(Ph(2)PF)(F)] (3) and the cyclometalated complex [(Ph(3)P)(2)Rh(Ph(2)PC(6)H(4))] (4). Both the chloroarene activation and the thermal decomposition reactions have been shown to occur via the facile and reversible F/Ph rearrangement reaction of 1 to cis-[(Ph(3)P)(2)Rh(Ph)(Ph(2)PF)] (5), which has been isolated and fully characterized. Kinetic studies of the F/Ph rearrangement, an intramolecular process not influenced by extra phosphine, have led to the determination of E(a) = 22.7 +/- 1.2 kcal mol(-)(1), DeltaH(++) = 22.0 +/- 1.2 kcal mol(-)(1), and DeltaS(++) = -10.0 +/- 3.7 eu. Theoretical studies of F/Ph exchange with the [(PH(3))(2)(PH(2)Ph)RhF] model system pointed to two possible mechanisms: (i) Ph transfer to Rh followed by F transfer to P (formally oxidative addition followed by reductive elimination, pathway 1) and (ii) F transfer to produce a metallophosphorane with subsequent Ph transfer to Rh (pathway 2). Although pathway 1 cannot be ruled out completely, the metallophosphorane mechanism finds more support from both our own and previously reported observations. Possible involvement of metallophosphorane intermediates in various P-F, P-O, and P-C bond-forming reactions at a metal center is discussed.

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“…The wealth of crystallographically characterized copper complexes with N 4 and N 2 Cl 2 ligation, as well as their corresponding Cu(II) ligand field region electronic absorption spectra, permits evaluation of the local metal center geometry using UV−vis spectroscopy . On the basis of the crystal structures of analogous tetrakispyridine complexes and simple ligand field theory arguments, the Cu(I) complexes 19 and 20 would be expected to possess tetrahedral geometry with a dihedral angle near 90°. − In contrast, Cu(II) complexes with N 4 and N 2 Cl 2 ligand fields can adopt coordination numbers from 4 to 6 and have geometries ranging from square planar , to cis , or trans − distorted-octahedral. Typically, 4-coordinate square planar complexes exhibit three optical absorption features ( 2 B 1g → 2 A 1g , 2 B 1g → 2 B 2g , 2 B 1g → 2 E g in D 4 h ) between 17 000 and 20 000 cm -1 corresponding to transitions from d z 2 , d xy , and d xz , yz to d x 2 - y 2 orbitals, respectively.…”

Section: Resultsmentioning

confidence: 99%

The Contribution of Ligand Flexibility to Metal Center Geometry Modulated Thermal Cyclization of Conjugated Pyridine and Quinoline Metalloenediynes of Copper(I) and Copper(II)

et al. 2001

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We report the syntheses, reactivities, and structure evaluations of a series of Cu(I) and Cu(II) metalloenediynes of conjugated 1,6-bis(pyridine-3)hex-3-ene-1,5-diyne (PyED, 7) and 1,6-bis(quinoline-3)hex-3-ene-1,5-diyne (QnED, 8) enediyne ligands, as well as their benzoenediyne analogues. Differential scanning calorimetry demonstrates that the [Cu(PyED)(2)](NO(3))(2) (11) exhibits a Bergman cyclization temperature (156 degrees C) which is dramatically reduced from that of the corresponding [Cu(PyED)(2)](PF(6)) (19) analogue (326 degrees C), indicating that large differences in the reactivities of these metalloenediynes can be accessed by variations in metal oxidation state. The distorted, 4-coordinate dichloride compound Cu(PyED)(Cl)(2) (15) exhibits a cyclization temperature (265 degrees C) between those of 11 and 19, suggesting that variation in geometry of the copper center is responsible for the wide range of reactivities. Similar results are obtained for the benzoenediyne and quinoline analogues. The structures of the Cu(II) systems have also been evaluated by a combination of electronic absorption and EPR spectroscopies which reveal tetragonal, 6-coordinate structures for the bis(enediyne) complexes, and tetrahedrally distorted 4-coordinate Cu(enediyne)Cl(2) species. For the bis(quinoline) enediyne derivatives 12 and 14 the larger g-anisotropy (g( parallel) = 2.27-2.28; g( perpendicular) = 2.06-2.07) indicates strong oxygen coordination from counterion. Molecular mechanics/dynamics calculations reveal that the geometries of these metal centers force the alkyne termini to a wide range of distances (3.85-4.20 A), thereby accounting for the variability in Bergman cyclization temperatures. Overall, the results show that ligand rigidity plays a prominent role in the conformational response of the enediyne to metal center geometry, which results in enhanced variations in the Bergman cyclization temperatures between complexes of different geometries.

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Über die Darstellung und die Kristallstruktur der Komplexverbindungen Ni(py)₄F₂ · 2H₂O und Cu(py)₄F₂ · 1,33 HF · 2H₂O

Abstract: Single crystals of Ni(py)

Cited by 14 publications

References 6 publications

Metalloenediynes: Ligand Field Control of Thermal Bergman Cyclization Reactions

Metalloenediynes: Ligand Field Control of Thermal Bergman Cyclization Reactions

The F/Ph Rearrangement Reaction of [(Ph₃P)₃RhF], the Fluoride Congener of Wilkinson's Catalyst

The Contribution of Ligand Flexibility to Metal Center Geometry Modulated Thermal Cyclization of Conjugated Pyridine and Quinoline Metalloenediynes of Copper(I) and Copper(II)

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Über die Darstellung und die Kristallstruktur der Komplexverbindungen Ni(py)4F2 · 2H2O und Cu(py)4F2 · 1,33 HF · 2H2O

Abstract: Single crystals of Ni(py)

Cited by 14 publications

References 6 publications

Metalloenediynes: Ligand Field Control of Thermal Bergman Cyclization Reactions

Metalloenediynes: Ligand Field Control of Thermal Bergman Cyclization Reactions

The F/Ph Rearrangement Reaction of [(Ph3P)3RhF], the Fluoride Congener of Wilkinson's Catalyst

The Contribution of Ligand Flexibility to Metal Center Geometry Modulated Thermal Cyclization of Conjugated Pyridine and Quinoline Metalloenediynes of Copper(I) and Copper(II)

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Über die Darstellung und die Kristallstruktur der Komplexverbindungen Ni(py)₄F₂ · 2H₂O und Cu(py)₄F₂ · 1,33 HF · 2H₂O

The F/Ph Rearrangement Reaction of [(Ph₃P)₃RhF], the Fluoride Congener of Wilkinson's Catalyst