Trapping of a Thiolate→Dibromine Charge‐Transfer Adduct by a Macrocyclic Dinickel Complex and Its Conversion into an Arenesulfenyl Bromide Derivative

Steinfeld, Gunther; Lozan, Vasile; Krüger, Hans‐Jörg; Kersting, Berthold

doi:10.1002/anie.200805028

Cited by 24 publications

(5 citation statements)

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“…Oxidation of the iron complex 5 with 1 equiv of iodine affords, after purification over silica gel, the cyclic bis-disulfide 1a in an 80% yield. Since iodine and bromine adducts of nickel thiolate as well as nickel sulfenyl bromide were reported in the literature, we suspected the intermediate formation of an iron(III) sulfenyl iodide during the course of iodine oxidation of 5 , but unfortunately we did not succeed in isolating any intermediate.…”

Section: Resultsmentioning

confidence: 91%

Reductive Metalation of Cyclic and Acyclic Pseudopeptidic Bis-Disulfides and Back Conversion of the Resulting Diamidato/Dithiolato Complexes to Bis-Disulfides

et al. 2010

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Cyclic and acyclic pseudopeptidic bis-disulfides built on an o-phenylene diamine scaffold were prepared: (N(2)H(2)S(2))(2), 1a, N(2)H(2)(S-SCH(3))(2), 1b, and N(2)H(2)(S-StBu)(2), 1c. Reductive metalation of these disulfides with (PF(6))[Cu(CH(3)CN)(4)] in the presence of Et(4)NOH as a base, or with (Et(4)N)[Fe(SEt)(4)] and Et(4)NCl, yields the corresponding diamidato/dithiolato copper(III) or iron(III) complex, (Et(4)N)[Cu(N(2)S(2))], 2, or (Et(4)N)(2)[Fe(N(2)S(2))Cl], 5. These complexes display characteristics similar to those previously described in the literature. The mechanism of the metalation with copper has been investigated by X-band electron paramagnetic resonance (EPR) spectroscopy at 10 K. After metalation of the bis-disulfide 1c and deprotonation of the amide nitrogens, the reductive cleavage of the S-S bonds occurs by two one-electron transfers leading to the intermediate formation of a copper(II) complex and a thyil radical. Complexes 2 and 5 can be converted back to the cyclic bis-disulfide 1a with iodine in an 80% yield. Reaction of 5 with iodine in the presence of CH(3)S-SCH(3) affords a 1/1 mixture of the acyclic N(2)H(2)(S-SCH(3))(2) disulfide 1b and cyclic bis-disulfide 1a. From 2, the reaction was monitored by (1)H NMR and gives 1b as major product. While there is no reaction of 2 or 5 with tBuS-StBu and iodine, reaction with an excess of tBuSI affords quantitatively the di-tert-butyl disulfide 1c. To assess the role of the Cu(III) oxidation state, control experiments were carried out under strictly anaerobic conditions with the copper(II) complex, (Et(4)N)(2)[Cu(N(2)S(2))], 6. Complex 6 is oxidized to 2 by iodine, and it reacts with an excess of tBuSI, yielding 1c as final product, through the intermediate formation of complex 2.

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Section: Resultsmentioning

confidence: 91%

Reductive Metalation of Cyclic and Acyclic Pseudopeptidic Bis-Disulfides and Back Conversion of the Resulting Diamidato/Dithiolato Complexes to Bis-Disulfides

et al. 2010

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“…Subsequently, a large number of self-assembled metallohelicates and other three-dimensional supramolecular structures have been obtained by variation of the metal components and the ligands. Some of these supramolecular assemblies can act as molecular hosts by encapsulating small molecular guests, which might undergo selective chemical transformations within the host molcule . A dramatic rate enhancement has been observed for selective transformations within metallosupramolecular hosts …”

Section: Introductionmentioning

confidence: 99%

“…Most of the three-dimensional metallosupramolecular structures are built from metal centers at the corners (often palladium or platinum species with cis -coordinated diamines or diphosphines as supporting ligands) that are linked by classical Werner-type polydentate ligands featuring nitrogen and/or oxygen donor atoms, such as pyrazine, 4,4′-bipyridine, or 2,4,6-tris(4-pyridyl)-1,3,5-triazine. , Polydentate ligands with carbon donors have rarely been used for the construction of metallosupramolecular assemblies, although some derivatives with bridging diisocyanide, acyclic diaminocarbenes, and remote N-heterocyclic carbene ligands have been described. Metallosupramolecular structures containing the ubiquitous N-heterocyclic carbenes (NHCs) as bridging ligands have been unknown until recently.…”

Section: Introductionmentioning

confidence: 99%

Supramolecular Structures from Polycarbene Ligands and Transition Metal Ions

et al. 2010

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The synthesis of cylinder-type carbene complexes from polycarbene ligands and coinage metal ions via metal-controlled self-assembly has been explored. Imidazole reacts with 1,2,4,5-tetrabromobenzene or 1,3,5-tribromobenzene to give 1,2,4,5-tetrakis(1-imidazolyl)benzene (1) and 1,3,5-tris(1-imidazolyl)benzene (3), respectively. The tetrakisimidazolium salts of type H4-2a,b(Br)4 and the trisimidazolium salts of type H3-4a,b(Br)3 have been prepared by alkylation of the remaining free imines of the tetrakis- and trisimidazoles (H4-2a 4+, H3-4a 3+: R = n-butyl; H4-2b 4+, H3-4b 3+: R = ethyl). Polyimidazolium salts H4-2a,b(PF6)4 and H3-4a,b(PF6)3 have been synthesized by anion exchange from H4-2a,b(Br)4 and H3-4a,b(Br)3. Two equivalents of tetraimidazolium salt H4-2a(Br)4 or H4-2a,b(PF6)4 reacts with four equivalents of Ag2O to yield via self-assembly molecular cylinders of type [Ag4(2a)2]Y4 (Y− = [AgBr2]− and/or Br−) or [Ag4(2a,b)2](PF6)4, respectively. Similarly, reaction of two equivalents of trisimidazolium salts H3-4a(Br)3 or H3-4a,b)(PF6)3 with three equivalents of Ag2O yields the molecular cylinder [Ag3(4a)2](Y)3 (Y− = [AgBr2]− and/or Br−) or [Ag3(4a,b)2](PF6)3, respectively. Transmetalation of [Ag4(2a,b)2](PF6)4 with four equivalents of [AuCl(SMe2)] leads to the formation of the tetranuclear gold(I) complex [Au4(2a,b)2](PF6)4 with retention of the metallosupramolecular assembly. Analogously, transmetalation of [Ag3(4a,b)2](PF6)3 with three equivalents of [AuCl(SMe2)] or CuBr yields the trinuclear gold(I) complexes [Au3(4a,b)2](PF6)3 or the copper(I) complexes [Cu3(4a,b)2](PF6)3, respectively. Contrary to the metallosupramolecular assemblies of type [M4(2a)2]4+ (M = Ag+, Au+), tetrakisimidazolium salt H4-2a(Br)4 reacts with K2PtCl4 in the presence of NaOAc to yield the square-planar dinuclear complex [Pt2(2a)Br4].

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“…( ii ) Carboxylate ions are biologically relevant molecules. − ( iii ) Nickel carboxylate bonding is of importance in bioinorganic , and biomimetic chemistry. , ( iv ) A systematic study of an isostructural series of carboxylato-bridged nickel(II) complexes has not appeared in the literature . ( v ) The characterization data of carboxylato-bridged [Ni II 2 L(μ-O 2 CR)] + complexes may serve as invaluable references for future studies aimed at regioselective carboxylate transformations. ,− ( vi ) Since the immediate environment of the carboxylate group in the dinuclear complexes is essentially the same, these systems should be well suited for the study of complex properties as a function of varying carboxylato coligand basicity.…”

Section: Introductionmentioning

confidence: 99%

Dependence of the Chemical Properties of Macrocyclic [Ni^II₂L(μ-O₂CR)]⁺ Complexes on the Basicity of the Carboxylato Coligands (L²⁻ = macrocyclic N₆S₂ ligand)

et al. 2010

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The dependence of the properties of mixed ligand [Ni(II)(2)L(μ-O(2)CR)](+) complexes (where L(2-) represents a 24-membered macrocyclic hexaamine-dithiophenolato ligand) on the basicity of the carboxylato coligands has been examined. For this purpose 19 different [Ni(II)(2)L(μ-O(2)CR)](+) complexes (2-20) incorporating carboxylates with pK(b) values in the range 9 to 14 have been prepared by the reaction of [Ni(II)(2)L(μ-Cl)](+) (1) and the respective sodium or triethylammonium carboxylates. The resulting carboxylato complexes, isolated as ClO(4)(-) or BPh(4)(-) salts, have been fully characterized by elemental analyses, IR, UV/vis spectroscopy, and X-ray crystallography. The possibility of accessing the [Ni(II)(2)L(μ-O(2)CR)](+) complexes by carboxylate exchange reactions has also been examined. The main findings are as follows: (i) Substitution reactions between 1 and NaO(2)CR are not affected by the basicity or the steric hindrance of the carboxylate. (ii) Complexes 2-20 form an isostructural series of bisoctahedral [Ni(II)(2)L(μ-O(2)CR)](+) compounds with a N(3)Ni(μ-SR)(2)(μ-O(2)CR)NiN(3) core. (iii) They are readily identified by their ν(as)(CO) and ν(s)(CO) stretching vibration bands in the ranges 1684-1576 cm(-1) and 1428-1348 cm(-1), respectively. (iv) The spin-allowed (3)A(2g) → (3)T(2g) (ν(1)) transition of the NiOS(2)N(3) chromophore is steadily red-shifted by about 7.5 nm per pK(b) unit with increasing pK(b) of the carboxylate ion. (v) The less basic the carboxylate ion, the more stable the complex. The stability difference across the series, estimated from the difference of the individual ligand field stabilization energies (LFSE), amounts to about 4.2 kJ/mol [Δ(LFSE)(2,18)]. (vi) The "second-sphere stabilization" of the nickel complexes is not reflected in the electronic absorption spectra, as these forces are aligned perpendicularly to the Ni-O bonds. (vii) Coordination of a basic carboxylate donor to the [Ni(II)(2)L](2+) fragment weakens its Ni-N and Ni-S bonds. This bond weakening is reflected in small but significant bond length changes. (viii) The [Ni(II)(2)L(μ-O(2)CR)](+) complexes are relatively inert to carboxylate exchange reactions, except for the formato complex [Ni(II)(2)L(μ-O(2)CH)](+) (8), which reacts with both more and less basic carboxylato ligands.

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Trapping of a Thiolate→Dibromine Charge‐Transfer Adduct by a Macrocyclic Dinickel Complex and Its Conversion into an Arenesulfenyl Bromide Derivative

Cited by 24 publications

References 23 publications

Reductive Metalation of Cyclic and Acyclic Pseudopeptidic Bis-Disulfides and Back Conversion of the Resulting Diamidato/Dithiolato Complexes to Bis-Disulfides

Reductive Metalation of Cyclic and Acyclic Pseudopeptidic Bis-Disulfides and Back Conversion of the Resulting Diamidato/Dithiolato Complexes to Bis-Disulfides

Supramolecular Structures from Polycarbene Ligands and Transition Metal Ions

Dependence of the Chemical Properties of Macrocyclic [Ni^II₂L(μ-O₂CR)]⁺ Complexes on the Basicity of the Carboxylato Coligands (L²⁻ = macrocyclic N₆S₂ ligand)

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Trapping of a Thiolate→Dibromine Charge‐Transfer Adduct by a Macrocyclic Dinickel Complex and Its Conversion into an Arenesulfenyl Bromide Derivative

Cited by 24 publications

References 23 publications

Reductive Metalation of Cyclic and Acyclic Pseudopeptidic Bis-Disulfides and Back Conversion of the Resulting Diamidato/Dithiolato Complexes to Bis-Disulfides

Reductive Metalation of Cyclic and Acyclic Pseudopeptidic Bis-Disulfides and Back Conversion of the Resulting Diamidato/Dithiolato Complexes to Bis-Disulfides

Supramolecular Structures from Polycarbene Ligands and Transition Metal Ions

Dependence of the Chemical Properties of Macrocyclic [NiII2L(μ-O2CR)]+ Complexes on the Basicity of the Carboxylato Coligands (L2− = macrocyclic N6S2 ligand)

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Dependence of the Chemical Properties of Macrocyclic [Ni^II₂L(μ-O₂CR)]⁺ Complexes on the Basicity of the Carboxylato Coligands (L²⁻ = macrocyclic N₆S₂ ligand)