Neutral and Cationic Zinc Complexes with N- and S‑Donor-Functionalized Cyclopentadienyl Ligands

The synthesis of neutral and cationic zinc cyclopentadienyl (Cp) complexes with amino and thio donor groups that are attached to the Cp ring via a side chain is reported. The amino-functionalized zincocene [ZnCp^3N₂] (<b>3</b>; Cp^3N = C₅Me₄(CH₂)₃NMe₂) was prepared in a salt metathesis reaction from KCp^3N and ZnCl₂. In the solid-state structure of <b>3</b>, which was determined by single-crystal X-ray diffraction, one of the Cp^3N ligands is coordinated as a chelating ligand through a ring carbon atom and through the amino group, whereas the other Cp^3N ligand is bound in a monodentate mode through the Cp ring only. A reaction of <b>3</b> with ZnEt₂, [ZnCp*₂] (Cp* = C₅Me₅), and [ZnCp^2N₂] (<b>2</b>; Cp^2N = C₅Me₄(CH₂)₂NMe₂) gave the heteroleptic complexes [ZnEtCp^3N] (<b>4</b>), [ZnCp*Cp^3N] (<b>5</b>), and [ZnCp^3NCp^2N] (<b>6</b>), respectively. The incorporation of a second amino group in the same side chain led to the formation of the mononuclear zinc chlorido complex [ZnClCp^tmeda] (<b>7</b>; Cp^tmeda = C₅Me₄(CH₂)₂NMe­(CH₂)₂NMe₂), in which the Cp^tmeda ligand is bound in a tridentate coordination mode. In addition, the thio-functionalized zincocene [ZnCp^2S₂] (<b>8</b>; Cp^2S = C₅Me₄(CH₂)₂SMe) was obtained and shown to exhibit an intramolecular coordination by the sulfur atoms. Starting from the neutral complexes <b>2</b>, <b>3</b>, and <b>8</b>, the cationic compounds [ZnCp^D(py)₂]⁺[BAr^F₄]⁻ (Cp^D = Cp^2N (<b>9</b>), Cp^3N (<b>10</b>), Cp^2S (<b>11</b>); py = pyridine; BAr^F₄ = B­{3,5-(CF₃)₂C₆H₃}₄) were obtained either by protonation or upon reaction with an electrophile in the presence of pyridine. In these cationic complexes the highly electrophilic zinc center is stabilized by intramolecular coordination through the donor groups