Unusual C–N Coupling Reactivity of Thiopyridazines: Efficient Synthesis of Iron Diorganotrisulfide Complexes

The reaction of iron­(II) triflate with 6-<i>tert</i>-butyl-3-thiopyridazine (PnH) and 4-methyl-6-<i>tert</i>-butyl-3-thiopyridazine (^MePnH) respectively led to iron bis­(diorganotrisulfide) complexes [Fe­(^RPnS₃Pn^R)₂]­(OTf)₂ [R = H (<b>1a</b>) and Me (<b>2a</b>)]. The corresponding perchlorate complexes were prepared by using the iron­(II) chloride precursor and the subsequent addition of 2 equiv of NaClO₄, giving [Fe­(^RPnS₃Pn^R)₂]­(ClO₄)₂ [R = H (<b>1b</b>) and Me (<b>2b</b>)]. The compounds were fully characterized including single-crystal X-ray diffraction analysis. All four compounds exhibit nearly perfect octahedral geometries with an iron center coordinated by four nitrogen atoms from two ^RPnS₃Pn^R ligands and by two sulfur atoms of the central atom in the S₃ unit. The diamagnetic complexes exhibit unusually high redox potentials for the Fe^2+/3+ couple at <i>E</i>_1/2 = 1.15 V (for <b>1a</b> and <b>1b</b>) and 1.08 V (for <b>2a</b> and <b>2b</b>) versus Fc/Fc⁺, respectively, as determined by cyclic voltammetry. Furthermore, the source of the extra sulfur atom within the S₃ unit was elucidated by isolation of C–N-coupled pyridazinylthiopyridazine products

Thiopyridazine-Based Palladium and Platinum Boratrane Complexes

Palladium and platinum boratrane complexes of the type [M­{B­(Pn^{Me,<i>t</i>Bu})₃}­(PPh₃)] (M = Pd <b>1</b>, Pt <b>2b</b>) have been prepared via the reaction of the soft scorpionate ligand potassium tris­(4-methyl-6-<i>tert</i>-butyl-3-thiopyridazinyl)­borate KTn^{Me,<i>t</i>Bu} with bis­(triphenylphosphine)­metal­(II) dichloride. While reaction with the Pd precursor allowed direct isolation of a symmetric boratrane complex, the Pt analogue led to the hydrido compound [Pt­{B­(Pn^{Me,<i>t</i>Bu})₃}­(PPh₃)­H]Cl (<b>2a</b>), which after reaction with a base gave <b>2b</b>. Subsequent oxidation with Br₂ and I₂, respectively, led to the dihalide compounds of the molecular formula [M­{B­(Pn^{Me,<i>t</i>Bu})₃}­X₂] (<b>3a</b>,<b>b</b>–<b>4a</b>,<b>b</b>). Halide abstraction with Ag­(SbF₆) further gave interesting cationic compounds of either dimeric [Pd­{B­(Pn^{Me,<i>t</i>Bu})₃}­X]₂(SbF₆)₂ (<b>5a</b>,<b>b</b>) or monomeric [Pd­{B­(Pn^{Me,<i>t</i>Bu})₃}­(NCMe)₂]­(SbF₆) (<b>6</b>) nature. All compounds were spectroscopically and X-ray crystallographically characterized revealing strong metal to boron interactions. DFT calculations of <b>1</b>, <b>2a</b>, and <b>2b</b> confirm the strong M–B interaction and a high positive charge on the metal centers

Three-Fold-Symmetric Selenium-Donor Metallaboratranes of Cobalt and Nickel

A novel selenium-containing pyridazinyl-based soft scorpionate ligand (KTnse) was synthesized. It reacts with CoCl₂ and NiCl₂, yielding the first metallaboratrane complexes with selenium in their donor positions. Further substitution with Ag­(OTf) or NaN₃ allows isolation of the respective triflate or azide complexes. Reaction with Ag­(OTf) leads in the case of nickel to a dinuclear, dicationic complex with a short Ni–Ni distance, while cobalt gave a mononuclear cationic species. Substitution of the chloride by azide yields with both metals the respective azide complexes. All compounds were characterized via single-crystal X-ray diffraction analysis. Density functional theory calculations on the chloride species point to oxidized cobalt­(III) and nickel­(III) centers

Synthesis and Characterization of a Thiopyridazinylmethane-Based Scorpionate Ligand: Formation of Zinc Complexes and Rearrangement Reaction

The ligand tris­(6-<i>tert</i>-butyl-3-thiopyridazinyl)­methane ([Tntm]­H) was synthesized by the reaction of 6-<i>tert</i>-butyl-3-thiopyridazine with bromoform and reacted with zinc bis­(trimethylsilylamide) (Zn­(N­{SiMe₃}₂)₂) to form [Tntm]­Zn­(N­{SiMe₃}₂) (<b>1</b>). This complex further reacts with protic and acidic substrates, generating the zinc thiolate complex [Tntm]­Zn­(S<i>t</i>Bu) (<b>2</b>) and zinc benzoate complex [Tntm]­Zn­(O₂C-Me₂C₆H₃) (<b>3a</b>). In all compounds [Tntm] was found to have tridentate coordination to the metal center in a κ³-<i>C,N,N</i> fashion, as established by single-crystal X-ray diffraction analyses. In solution, rapid dynamic κ³/κ⁴ equilibrium occurs at room temperature, while ¹H NMR spectroscopy at −30 °C confirms the asymmetric solid-state structure. Furthermore, complex <b>3a</b> shows a rearrangement reaction in solution where the ligand isomerizes to give a κ⁴-<i>C,N,N,S</i> (<b>3b</b>) and a κ⁴-<i>C,N,S,S</i> isomer (<b>3c</b>), respectively. Density functional theory (DFT) calculations reveal <b>3b</b> and <b>3c</b> to be 13.7 and 15.6 kJ/mol more stable in methylene chloride than <b>3a</b>, respectively. All compounds were fully characterized via ¹H, ¹³C, and variable temperature NMR spectroscopy, as well as elemental and single-crystal X-ray diffraction analysis

Synthesis and Characterization of a Thiopyridazinylmethane-Based Scorpionate Ligand: Formation of Zinc Complexes and Rearrangement Reaction

The ligand tris­(6-<i>tert</i>-butyl-3-thiopyridazinyl)­methane ([Tntm]­H) was synthesized by the reaction of 6-<i>tert</i>-butyl-3-thiopyridazine with bromoform and reacted with zinc bis­(trimethylsilylamide) (Zn­(N­{SiMe₃}₂)₂) to form [Tntm]­Zn­(N­{SiMe₃}₂) (<b>1</b>). This complex further reacts with protic and acidic substrates, generating the zinc thiolate complex [Tntm]­Zn­(S<i>t</i>Bu) (<b>2</b>) and zinc benzoate complex [Tntm]­Zn­(O₂C-Me₂C₆H₃) (<b>3a</b>). In all compounds [Tntm] was found to have tridentate coordination to the metal center in a κ³-<i>C,N,N</i> fashion, as established by single-crystal X-ray diffraction analyses. In solution, rapid dynamic κ³/κ⁴ equilibrium occurs at room temperature, while ¹H NMR spectroscopy at −30 °C confirms the asymmetric solid-state structure. Furthermore, complex <b>3a</b> shows a rearrangement reaction in solution where the ligand isomerizes to give a κ⁴-<i>C,N,N,S</i> (<b>3b</b>) and a κ⁴-<i>C,N,S,S</i> isomer (<b>3c</b>), respectively. Density functional theory (DFT) calculations reveal <b>3b</b> and <b>3c</b> to be 13.7 and 15.6 kJ/mol more stable in methylene chloride than <b>3a</b>, respectively. All compounds were fully characterized via ¹H, ¹³C, and variable temperature NMR spectroscopy, as well as elemental and single-crystal X-ray diffraction analysis

Synthesis and Characterization of a Thiopyridazinylmethane-Based Scorpionate Ligand: Formation of Zinc Complexes and Rearrangement Reaction

The ligand tris­(6-<i>tert</i>-butyl-3-thiopyridazinyl)­methane ([Tntm]­H) was synthesized by the reaction of 6-<i>tert</i>-butyl-3-thiopyridazine with bromoform and reacted with zinc bis­(trimethylsilylamide) (Zn­(N­{SiMe₃}₂)₂) to form [Tntm]­Zn­(N­{SiMe₃}₂) (<b>1</b>). This complex further reacts with protic and acidic substrates, generating the zinc thiolate complex [Tntm]­Zn­(S<i>t</i>Bu) (<b>2</b>) and zinc benzoate complex [Tntm]­Zn­(O₂C-Me₂C₆H₃) (<b>3a</b>). In all compounds [Tntm] was found to have tridentate coordination to the metal center in a κ³-<i>C,N,N</i> fashion, as established by single-crystal X-ray diffraction analyses. In solution, rapid dynamic κ³/κ⁴ equilibrium occurs at room temperature, while ¹H NMR spectroscopy at −30 °C confirms the asymmetric solid-state structure. Furthermore, complex <b>3a</b> shows a rearrangement reaction in solution where the ligand isomerizes to give a κ⁴-<i>C,N,N,S</i> (<b>3b</b>) and a κ⁴-<i>C,N,S,S</i> isomer (<b>3c</b>), respectively. Density functional theory (DFT) calculations reveal <b>3b</b> and <b>3c</b> to be 13.7 and 15.6 kJ/mol more stable in methylene chloride than <b>3a</b>, respectively. All compounds were fully characterized via ¹H, ¹³C, and variable temperature NMR spectroscopy, as well as elemental and single-crystal X-ray diffraction analysis