Phosphazenbasierte Chelatkomplexe der Seltenerdmetalle: Spektroskopie, Struktur und katalytische Reaktivität in nachhaltigen chemischen Prozessen

Die Organometallchemie der Seltenerdmetalle (SEM) befindet sich seit nunmehr 40 Jahren in einer rasanten Entwicklung. Die große Hoffnung auf mehr Nachhaltigkeit in der Nutzung unserer begrenzten Rohstoff-Ressourcen beruht unter anderem auf dem katalytischen Potential der SEM. Zu den SEM zählen 17 (Elemente der Gruppe 3 und der Lanthanoide) wenig erforschte und doch nicht so selten vorkommende Metalle des Periodensystems. Diese Arbeit beschäftigte sich mit der Synthese, Struktur, Spektroskopie sowie der gezielten Modifizierung neuartiger, meist paramagnetischer SEM-Komplexe und deren Einsatz in der metallorganischen Katalyse. In der Arbeit konnte gezeigt werden, dass die phosphazenbasierte Iminophosphonamid-(NPN-) und Cyclopentadienyl-phosphazen-(CpPN-)Liganden stabile und gleichzeitig reaktive Komplexe der SEM liefern und interessante Reaktivitätsstudien für die Isolierung katalytisch aktiver Spezies sowie wichtige Katalysen ermöglichen. Ein großer Wert wurde bei der Charakterisierung der Komplexe auf die NMR-Spektroskopie, inklusive der Signalzuordnung der paramagnetischen Komplexe, und Kristallstrukturanalyse gelegt. Die erfolgreichen Katalysen waren die Hydroaminierung von Olefinen, die Polymerisation von Isopren zu synthetischem Kautschuk und die ringöffnende Polymerisation von zyklischen Estern zu biologisch abbaubaren Kunststoffen

Phosphazenbasierte Chelatkomplexe der Seltenerdmetalle: Spektroskopie, Struktur und katalytische Reaktivität in nachhaltigen chemischen Prozessen

Die Organometallchemie der Seltenerdmetalle (SEM) befindet sich seit nunmehr 40 Jahren in einer rasanten Entwicklung. Die große Hoffnung auf mehr Nachhaltigkeit in der Nutzung unserer begrenzten Rohstoff-Ressourcen beruht unter anderem auf dem katalytischen Potential der SEM. Zu den SEM zählen 17 (Elemente der Gruppe 3 und der Lanthanoide) wenig erforschte und doch nicht so selten vorkommende Metalle des Periodensystems. Diese Arbeit beschäftigte sich mit der Synthese, Struktur, Spektroskopie sowie der gezielten Modifizierung neuartiger, meist paramagnetischer SEM-Komplexe und deren Einsatz in der metallorganischen Katalyse. In der Arbeit konnte gezeigt werden, dass die phosphazenbasierte Iminophosphonamid-(NPN-) und Cyclopentadienyl-phosphazen-(CpPN-)Liganden stabile und gleichzeitig reaktive Komplexe der SEM liefern und interessante Reaktivitätsstudien für die Isolierung katalytisch aktiver Spezies sowie wichtige Katalysen ermöglichen. Ein großer Wert wurde bei der Charakterisierung der Komplexe auf die NMR-Spektroskopie, inklusive der Signalzuordnung der paramagnetischen Komplexe, und Kristallstrukturanalyse gelegt. Die erfolgreichen Katalysen waren die Hydroaminierung von Olefinen, die Polymerisation von Isopren zu synthetischem Kautschuk und die ringöffnende Polymerisation von zyklischen Estern zu biologisch abbaubaren Kunststoffen

Yttrium Hydride Complex Bearing CpPN/Amidinate Heteroleptic Ligands: Synthesis, Structure, and Reactivity

The reaction of the yttrium dialkyls (C₅H₄–PPh₂N–C₆H₃^<i>i</i>Pr₂)­Y­(CH₂SiMe₃)₂(thf) (<b>1</b>) with an excess of <i>N</i>,<i>N′</i>-diisopropylcarbodiimide gave the yttrium monoalkyl complex (C₅H₄–PPh₂N–C₆H₃^<i>i</i>Pr₂)­Y­(CH₂SiMe₃)­[^<i>i</i>PrNC­(CH₂SiMe₃)–N^<i>i</i>Pr] (<b>2</b>). <b>2</b> subsequently reacted with 1 equiv of PhSiH₃ to generate the CpPN/amidinate heteroleptic yttrium hydride {(C₅H₄–PPh₂N–C₆H₃^<i>i</i>Pr₂)­Y­[^<i>i</i>PrNC­(CH₂SiMe₃)–N^<i>i</i>Pr]­(μ-H)}₂ (<b>3</b>). Hydride <b>3</b> showed good reactivity toward various substrates containing unsaturated C–C, C–N, and N–N bonds, such as azobenzene, <i>p</i>-tolyacetylene, 1,4-bis­(trimethylsilyl)-1,3-butanediyne, <i>N</i>,<i>N′</i>-diisopropylcarbodiimide, and 4-dimethylaminopyridine, affording the yttrium hydrazide complex <b>4</b> with a rare η²-Cp bonding mode, yttrium terminal alkynyl complex <b>5</b>, yttrium η³-propargyl complex <b>6</b>, yttrium amidinate complex <b>7</b>, and yttrium 2-hydro-4-dimethylaminopyridyl product <b>8</b>, respectively

Yttrium Hydride Complex Bearing CpPN/Amidinate Heteroleptic Ligands: Synthesis, Structure, and Reactivity

The reaction of the yttrium dialkyls (C₅H₄–PPh₂N–C₆H₃^<i>i</i>Pr₂)­Y­(CH₂SiMe₃)₂(thf) (<b>1</b>) with an excess of <i>N</i>,<i>N′</i>-diisopropylcarbodiimide gave the yttrium monoalkyl complex (C₅H₄–PPh₂N–C₆H₃^<i>i</i>Pr₂)­Y­(CH₂SiMe₃)­[^<i>i</i>PrNC­(CH₂SiMe₃)–N^<i>i</i>Pr] (<b>2</b>). <b>2</b> subsequently reacted with 1 equiv of PhSiH₃ to generate the CpPN/amidinate heteroleptic yttrium hydride {(C₅H₄–PPh₂N–C₆H₃^<i>i</i>Pr₂)­Y­[^<i>i</i>PrNC­(CH₂SiMe₃)–N^<i>i</i>Pr]­(μ-H)}₂ (<b>3</b>). Hydride <b>3</b> showed good reactivity toward various substrates containing unsaturated C–C, C–N, and N–N bonds, such as azobenzene, <i>p</i>-tolyacetylene, 1,4-bis­(trimethylsilyl)-1,3-butanediyne, <i>N</i>,<i>N′</i>-diisopropylcarbodiimide, and 4-dimethylaminopyridine, affording the yttrium hydrazide complex <b>4</b> with a rare η²-Cp bonding mode, yttrium terminal alkynyl complex <b>5</b>, yttrium η³-propargyl complex <b>6</b>, yttrium amidinate complex <b>7</b>, and yttrium 2-hydro-4-dimethylaminopyridyl product <b>8</b>, respectively

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