Phosphazene-Functionalized Cyclopentadienyl and Its Derivatives Ligated Rare-Earth Metal Alkyl Complexes: Synthesis, Structures, and Catalysis on Ethylene Polymerization

Treatment of Ln­(CH₂SiMe₃)₃(thf)₂ (Ln = Sc, Y, and Lu) with 1 equiv of CpPN-type ligands C₅H₄PPh₂–NH–C₆H₃R₂ (R = Me, <b>L¹(Me)</b>; R = ^<i>i</i>Pr, <b>L¹(^<i>i</i>Pr)</b>) at room temperature readily generated the corresponding CpPN-type bis­(alkyl) complexes <b>1</b> and <b>2a</b>–<b>2c</b>. Addition of 3 equiv of LiCH₂SiMe₃ to a mixture of <b>L¹(^<i>i</i>Pr)</b> and LnCl₃(thf)₂ (Ln = Sm and Nd) also afforded the CpPN-type bis­(alkyl) complexes <b>2d</b> and <b>2e</b>. The Cp moiety bonds to the central metal in a classical η⁵ mode in all CpPN-type complexes <b>1</b> and <b>2</b>. In contrast, the Cp^MePN-type ligands C₅Me₄H–PPh₂N–C₆H₃R₂ (R = Me, <b>L²(Me)</b>; R = ^<i>i</i>Pr, <b>L²(^<i>i</i>Pr)</b>) behaved differently. <b>L²(Me)</b> did not react with Sc­(CH₂SiMe₃)₃(thf)₂. Similarly, <b>L²(^<i>i</i>Pr)</b> was also inert to Sc­(CH₂SiMe₃)₃(thf)₂ even at 50 °C. When the central metal was changed to yttrium, however, the equimolar reaction between Y­(CH₂SiMe₃)₃(thf)₂ and <b>L²(^<i>i</i>Pr)</b> in the presence of LiCl afforded two bis­(alkyl) complexes <b>3a</b> and <b>3b</b>. In the main product <b>3a</b>, [C₅HMe₃(η³-CH₂)–PPh₂N–C₆H₃^<i>i</i>Pr₂]­Y­(CH₂SiMe₃)₂(thf), the ligand bonds to the Y³⁺ ion in a rare η³-allyl/κ-N mode, whereas in <b>3b</b>, <b>(</b>C₅Me₄–PPh₂N–C₆H₃^<i>i</i>Pr₂)­Y­(CH₂SiMe₃)₂(LiCl)­(thf), the Cp ring coordinates to the Y³⁺ ion in an η⁵ mode, and a LiCl unit is located between the Y³⁺ ion and the nitrogen atom. When the central metal was changed to lutetium, a bis­(alkyl) complex <b>4a</b>, [C₅HMe₃(η³-CH₂)–PPh₂N–C₆H₃^<i>i</i>Pr₂]­Lu­(CH₂SiMe₃)₂(thf), and a bis­(alkyl) complex <b>4b</b>, (C₅Me₄–PPh₂N–C₆H₃^<i>i</i>Pr₂)­Lu­(CH₂SiMe₃)₂, were isolated. The protonolysis reaction of the IndPN-type ligands C₉H₇–PPh₂N–C₆H₃R₂ (R = Me, <b>L³(Me)</b>; R = Et, <b>L³(Et)</b>; R = ^<i>i</i>Pr, <b>L³(^<i>i</i>Pr)</b>) with Ln­(CH₂SiMe₃)₃(thf)₂ (Ln = Sc, Y, and Lu) generated the IndPN-type bis­(alkyl) complexes <b>5a</b>–<b>5c</b>, <b>6</b>, and <b>7a</b>–<b>7c</b>, selectively, where the Ind moiety tends to adopt an η³-bonding fashion. The more bulky FluPN-type ligands C₁₃H₉–PPh₂N–C₆H₄R (R = H, <b>L⁴(H)</b>; R = Me, <b>L⁴(Me)</b>) were treated with Ln­(CH₂SiMe₃)₃(thf)₂ (Ln = Sc and Lu) to afford the FluPN-type bis­(alkyl) complexes <b>8</b> and <b>9a</b> and <b>9b</b>, where the Flu moiety has a rare η¹-bonding mode. Complexes <b>1</b>–<b>9</b> were fully characterized by ¹H, ¹³C, and ³¹P NMR; X-ray; and elemental analyses. Upon activation with AlR₃ and [Ph₃C]­[B­(C₆F₅)₄], the scandium complexes showed good to high catalytic activity for ethylene polymerization. The effects of the sterics and electronics of the ligand, the loading and the type of AlR₃, the polymerization temperature, and the polymerization time on the catalytic activity were also discussed

Phosphazene-Functionalized Cyclopentadienyl and Its Derivatives Ligated Rare-Earth Metal Alkyl Complexes: Synthesis, Structures, and Catalysis on Ethylene Polymerization

Treatment of Ln­(CH₂SiMe₃)₃(thf)₂ (Ln = Sc, Y, and Lu) with 1 equiv of CpPN-type ligands C₅H₄PPh₂–NH–C₆H₃R₂ (R = Me, <b>L¹(Me)</b>; R = ^<i>i</i>Pr, <b>L¹(^<i>i</i>Pr)</b>) at room temperature readily generated the corresponding CpPN-type bis­(alkyl) complexes <b>1</b> and <b>2a</b>–<b>2c</b>. Addition of 3 equiv of LiCH₂SiMe₃ to a mixture of <b>L¹(^<i>i</i>Pr)</b> and LnCl₃(thf)₂ (Ln = Sm and Nd) also afforded the CpPN-type bis­(alkyl) complexes <b>2d</b> and <b>2e</b>. The Cp moiety bonds to the central metal in a classical η⁵ mode in all CpPN-type complexes <b>1</b> and <b>2</b>. In contrast, the Cp^MePN-type ligands C₅Me₄H–PPh₂N–C₆H₃R₂ (R = Me, <b>L²(Me)</b>; R = ^<i>i</i>Pr, <b>L²(^<i>i</i>Pr)</b>) behaved differently. <b>L²(Me)</b> did not react with Sc­(CH₂SiMe₃)₃(thf)₂. Similarly, <b>L²(^<i>i</i>Pr)</b> was also inert to Sc­(CH₂SiMe₃)₃(thf)₂ even at 50 °C. When the central metal was changed to yttrium, however, the equimolar reaction between Y­(CH₂SiMe₃)₃(thf)₂ and <b>L²(^<i>i</i>Pr)</b> in the presence of LiCl afforded two bis­(alkyl) complexes <b>3a</b> and <b>3b</b>. In the main product <b>3a</b>, [C₅HMe₃(η³-CH₂)–PPh₂N–C₆H₃^<i>i</i>Pr₂]­Y­(CH₂SiMe₃)₂(thf), the ligand bonds to the Y³⁺ ion in a rare η³-allyl/κ-N mode, whereas in <b>3b</b>, <b>(</b>C₅Me₄–PPh₂N–C₆H₃^<i>i</i>Pr₂)­Y­(CH₂SiMe₃)₂(LiCl)­(thf), the Cp ring coordinates to the Y³⁺ ion in an η⁵ mode, and a LiCl unit is located between the Y³⁺ ion and the nitrogen atom. When the central metal was changed to lutetium, a bis­(alkyl) complex <b>4a</b>, [C₅HMe₃(η³-CH₂)–PPh₂N–C₆H₃^<i>i</i>Pr₂]­Lu­(CH₂SiMe₃)₂(thf), and a bis­(alkyl) complex <b>4b</b>, (C₅Me₄–PPh₂N–C₆H₃^<i>i</i>Pr₂)­Lu­(CH₂SiMe₃)₂, were isolated. The protonolysis reaction of the IndPN-type ligands C₉H₇–PPh₂N–C₆H₃R₂ (R = Me, <b>L³(Me)</b>; R = Et, <b>L³(Et)</b>; R = ^<i>i</i>Pr, <b>L³(^<i>i</i>Pr)</b>) with Ln­(CH₂SiMe₃)₃(thf)₂ (Ln = Sc, Y, and Lu) generated the IndPN-type bis­(alkyl) complexes <b>5a</b>–<b>5c</b>, <b>6</b>, and <b>7a</b>–<b>7c</b>, selectively, where the Ind moiety tends to adopt an η³-bonding fashion. The more bulky FluPN-type ligands C₁₃H₉–PPh₂N–C₆H₄R (R = H, <b>L⁴(H)</b>; R = Me, <b>L⁴(Me)</b>) were treated with Ln­(CH₂SiMe₃)₃(thf)₂ (Ln = Sc and Lu) to afford the FluPN-type bis­(alkyl) complexes <b>8</b> and <b>9a</b> and <b>9b</b>, where the Flu moiety has a rare η¹-bonding mode. Complexes <b>1</b>–<b>9</b> were fully characterized by ¹H, ¹³C, and ³¹P NMR; X-ray; and elemental analyses. Upon activation with AlR₃ and [Ph₃C]­[B­(C₆F₅)₄], the scandium complexes showed good to high catalytic activity for ethylene polymerization. The effects of the sterics and electronics of the ligand, the loading and the type of AlR₃, the polymerization temperature, and the polymerization time on the catalytic activity were also discussed