9 research outputs found
Facile Preparation of a Scandium Terminal Imido Complex Supported by a Phosphazene Ligand
The
scandium bisÂ(alkyl) complex bearing the phosphazene ligand
L<sup>1</sup>ScÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub> (<b>1</b>) (L<sup>1</sup> = NÂ(PPh<sub>2</sub>î—»NPh)<sub>2</sub>) reacted with an equimolar amount of 2,6-diisopropylaniline to afford
the corresponding mixed alkyl/anilido complex L<sup>1</sup>ScÂ[NHC<sub>6</sub>H<sub>3</sub>(<sup><i>i</i></sup>Pr)<sub>2</sub>]Â(CH<sub>2</sub>SiMe<sub>3</sub>) (<b>2</b>). Under mild conditions
(20 °C, 4 h or 0 °C, 12 h), complex <b>2</b> could
be swiftly transformed to the terminal imido complex L<sup>1</sup>Scî—»NÂ[C<sub>6</sub>H<sub>3</sub>(<sup><i>i</i></sup>Pr)<sub>2</sub>]Â(DMAP)<sub>2</sub> (<b>4</b>) in the presence
of DMAP (DMAP = 4-<i>N,N</i>-dimethylaminopyridine). Correspondingly,
treatment of the yttrium and lutetium bisÂ(alkyl) complexes L<sup>2</sup>LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub> (L<sup>2</sup> = NÂ[Ph<sub>2</sub>PNC<sub>6</sub>H<sub>3</sub>(<sup><i>i</i></sup>Pr)<sub>2</sub>]<sub>2</sub>; Ln = Y (<b>7</b>), Lu (<b>8</b>)) with equimolar amounts of 2,6-diisopropylaniline gave
the mixed alkyl/anilido complexes L<sup>2</sup>LnÂ[NHC<sub>6</sub>H<sub>3</sub>(<sup><i>i</i></sup>Pr)<sub>2</sub>]Â(CH<sub>2</sub>SiMe<sub>3</sub>) (Ln = Y (<b>9</b>), Lu (<b>10</b>)),
which, however, underwent dealkylation of the Ln–CH<sub>2</sub>SiMe<sub>3</sub> species at temperatures of 60 °C for <b>9</b> and 100 °C for <b>10</b> to afford bisÂ(anilido)
complexes L<sup>2</sup>LnÂ[NHC<sub>6</sub>H<sub>3</sub>(<sup><i>i</i></sup>Pr)<sub>2</sub>]<sub>2</sub> (Ln = Y (<b>11</b>), Lu (<b>12</b>)) as redistribution products. All these complexes
have been characterized by <sup>1</sup>H, <sup>13</sup>CÂ{<sup>1</sup>H}, and <sup>31</sup>PÂ{<sup>1</sup>H} NMR spectroscopy and X-ray
diffraction analyses, and clear structural insight into the behavior
of an imido functionality on a lanthanide metal center was provided
Rare-Earth-Metal Complexes Bearing Phosphazene Ancillary Ligands: Structures and Catalysis toward Highly Trans-1,4-Selective (Co)Polymerizations of Conjugated Dienes
The bis-arylated phosphazene compounds [HNÂ(PPh<sub>2</sub>NAr)<sub>2</sub>] (Ar = phenyl (HL<sup>1</sup>), 2,6-dimethylphenyl
(HL<sup>2</sup>), 2,6-diisopropylphenyl (HL<sup>3</sup>)) and the
imidodiphosphinate
compound HNÂ(PPh<sub>2</sub>O)<sub>2</sub> (HL<sup>4</sup>) have been
prepared via the Staudinger reaction. Treatment of the neutral compounds
HL<sup>1</sup>, HL<sup>2</sup>, and HL<sup>3</sup> with LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(THF)<sub>2</sub> (Ln = Sc, Y,
Lu) generated the solvent-free bisÂ(alkyl) complexes L<sup>1</sup>LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub> (Ln = Sc (<b>1a</b>),
Y (<b>1b</b>), Lu (<b>1c</b>)), L<sup>2</sup>ScÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub> (<b>2a</b>), L<sup>3</sup>YÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub> (<b>3b</b>),
and L<sup>3</sup>LuÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub> (<b>3c</b>), respectively. The reaction between HL<sup>4</sup> and
YÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(THF)<sub>2</sub> gave
the rare zwitterionic complex <b>4b</b>. Lithiation of the ligand
HL<sup>1</sup> by <i>n</i>BuLi followed by a metathesis
reaction with NdÂ(BH<sub>4</sub>)<sub>3</sub>(THF)<sub>3</sub> afforded
the corresponding complex L<sup>1</sup>NdÂ(BH<sub>4</sub>)<sub>2</sub>(THF)<sub>2</sub> (<b>5</b>). Complexes <b>1</b> upon
incorporation of [Ph<sub>3</sub>C]Â[BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>] and Al<i>i</i>Bu<sub>3</sub> led to ternary systems
that initiated isoprene polymerization with high activities, among
which complex <b>1a</b> was the first example of a scandium
catalytic precursor providing trans-1,4-selectivity (90.0%), while
the lutetium analogue <b>1c</b> had medium trans-1,4-selectivity
(54.3%) and the yttrium complex <b>1b</b> exhibited high cis-1,4-selectivity
(76.3%). The ternary system based on the zwitterion <b>4b</b> displayed the highest activity for the isoprene polymerization among
these complexes and gave cis-1,4-regularity-enriched polyisoprene
(70.6%). Highly stereospecific homopolymerizations of isoprene (trans-1,4-content:
97.0%) and butadiene (trans-1,4-content: 94.0%) were achieved by using
the borohydrido complex <b>5</b> upon the activation of dibutylmagnesium.
The copolymerization of isoprene and butadiene with <b>1a</b>/[Ph<sub>3</sub>C]Â[BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>/Al<i>i</i>Bu<sub>3</sub>] gave randomly arranged trans-1,4-regulated
polybutadiene and polyisoprene sequences. The kinetics study displayed
competitive polymerization rates of <i>r</i><sub>BD</sub> = 2.89 and <i>r</i><sub>IP</sub> = 0.41. The thermal behaviors
of the (co)Âpolymers were investigated
Phosphinimino-amino Magnesium Complexes: Synthesis and Catalysis of Heteroselective ROP of <i>rac</i>-Lactide
Alkane
elimination reactions of phosphinimino-amine ligands HL<sup>1–8</sup> ((2,6-Me<sub>2</sub>-C<sub>6</sub>H<sub>3</sub>NH)ÂCÂ(Ph)î—»CHPPh<sub>2</sub>(NAr) (Ar = C<sub>6</sub>H<sub>5</sub> (HL<sup>1</sup>); 2,6-Me<sub>2</sub>-C<sub>6</sub>H<sub>3</sub> (HL<sup>2</sup>); 2,6-Et<sub>2</sub>-C<sub>6</sub>H<sub>3</sub> (HL<sup>3</sup>); 2,6-<sup><i>i</i></sup>Pr<sub>2</sub>-C<sub>6</sub>H<sub>3</sub> (HL<sup>4</sup>);
2-OMe-C<sub>6</sub>H<sub>4</sub> (HL<sup>5</sup>); 2-Cl-C<sub>6</sub>H<sub>4</sub> (HL<sup>6</sup>); 3-CF<sub>3</sub>-C<sub>6</sub>H<sub>4</sub> (HL<sup>7</sup>); 4-MeO-C<sub>6</sub>H<sub>4</sub> (HL<sup>8</sup>)) with Mg<sup><i>n</i></sup>Bu<sub>2</sub>, respectively,
afforded a series of phosphinimino-amine-based complexes L<sup>1–8</sup>Mg<sup><i>n</i></sup>BuÂ(THF) (<b>1</b>–<b>8</b>) by releasing butane. Complexes <b>1</b>–<b>8</b> are phosphinimino-amine-ligated THF-solvated monoÂ(alkyl)Âs,
among which <b>1</b>–<b>4</b> adopt twisted tetrahedral
geometries, whereas <b>5</b> contains a trigonal bipyramido
geometry core. Complexes <b>1</b>–<b>8</b> all
display high activity for the ring-opening polymerization of <i>rac</i>-lactide. The molecular weights of the resulting PLA
are close to the theoretic values, and the molecular weight distributions
are narrow. Moreover, these complexes show medium to high heteroselectivity,
which, interestingly, increases with the decrease of the ligand steric
hindrance; thus, complex <b>1</b>, bearing a less bulky ligand,
exhibits a heteroselectivity of <i>P</i><sub>r</sub> = 0.98,
the highest value of a magnesium-based initiator achieved to date.
The kinetics study showed that the polymerization rate is first-order
dependent on both monomer and initiator concentrations, and the overall
rate equation is −dÂ[LA]/d<i>t</i> = 3.78 M<sup>–1</sup> s<sup>–1</sup> [LA]Â[Mg]
Efficient and Heteroselective Heteroscorpionate Rare-Earth-Metal Zwitterionic Initiators for ROP of <i>rac</i>-Lactide: Role of σ‑Ligand
A series of oxophosphine (3,5-Me<sub>2</sub>Pz)<sub>2</sub>CHPÂ(R)<sub>2</sub>O (Pz = pyrazole; R = <sup><i>t</i></sup>Bu (HL<sup>1</sup>), Cy (HL<sup>2</sup>))
and iminophosphine (3,5-Me<sub>2</sub>Pz)<sub>2</sub>CHPÂ(R)<sub>2</sub>NAr (R = Cy, Ar = Ph (HL<sup>3</sup>); R = Ph, Ar = Ph (HL<sup>4</sup>), Ar = 2,6-Me<sub>2</sub>-phenyl
(HL<sup>5</sup>)) heteroscorpionate ligands were synthesized. Abstraction
of the methide proton of these ligands by rare-earth-metal trisÂ(alkyl)Âs,
LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(THF)<sub>2</sub>, afforded
the corresponding zwitterionic bisÂ(alkyl) complexes L<sup>1–5</sup>LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(THF) (L<sup>1</sup>, Ln = Y (<b>1a</b>), Lu (<b>1b</b>); L<sup>2</sup>,
Ln = Y (<b>2a</b>), Lu (<b>2b</b>); L<sup>3</sup>, Ln
= Y (<b>3a</b>), Lu (<b>3b</b>); L<sup>4</sup>, Ln = Y
(<b>4a</b>), Lu (<b>4b</b>); L<sup>5</sup>, Ln = Y (<b>5a</b>), Lu (<b>5b</b>), while metathesis reaction of the
lithium salts of LiL<sup>3</sup> and LiL<sup>4</sup> with YCl<sub>3</sub>(THF)<sub>2</sub> or YBr<sub>3</sub>(THF)<sub>2</sub> followed
by treatment with LiCH<sub>2</sub>SiMe<sub>3</sub> and KNÂ(SiHMe<sub>2</sub>)<sub>2</sub>, respectively, afforded the first heteroscorpionate
yttrium mixed halogen/alkyl or amido complexes L<sup>3–4</sup>YÂ(Cl)Â(CH<sub>2</sub>SiMe<sub>3</sub>)Â(THF) (L<sup>3</sup> (<b>6a</b>), L<sup>4</sup> (<b>7a</b>)), L<sup>3–4</sup>YÂ(Cl)Â(NÂ(SiHMe<sub>2</sub>)<sub>2</sub>)Â(THF) (L<sup>3 </sup>(<b>8a</b>), L<sup>4</sup> (<b>9a</b>)), L<sup>4</sup>YÂ(Br)Â(CH<sub>2</sub>SiMe<sub>3</sub>)Â(THF) (<b>10a</b>), and
L<sup>4</sup>YÂ(Br)Â(NÂ(SiHMe<sub>2</sub>)<sub>2</sub>)Â(THF) (<b>11a</b>). The structures of these complexes were well-defined, and the molecular
structures of <b>1a</b>, <b>2a</b>, <b>3b</b>, <b>4b</b>, <b>5a</b>, and <b>7a</b> were further characterized
by single crystal X-ray diffraction analysis. Complexes <b>1</b>–<b>5</b> showed similar high activity toward the ROP
of <i>rac</i>-LA at room temperature, and both the alkyl
species participated in initiation, of which the lutetium complexes
exhibited slightly higher selectivity than their yttrium analogues
(<i>P</i><sub>r</sub> = 0.85–0.89 vs 0.80–0.84)
despite the bulkiness of the ligands. Interestingly, the mixed halogen
complexes <b>6a</b>–<b>11a</b> were single-site
initiators, where the σ-halogen moiety remaining on the central
metal showed, for the first time, facilitating the heteroselectivity
up to <i>P</i><sub>r</sub> = 0.98. This result sheds new
light on designing specifically selective catalytic precursors
Efficient and Heteroselective Heteroscorpionate Rare-Earth-Metal Zwitterionic Initiators for ROP of <i>rac</i>-Lactide: Role of σ‑Ligand
A series of oxophosphine (3,5-Me<sub>2</sub>Pz)<sub>2</sub>CHPÂ(R)<sub>2</sub>O (Pz = pyrazole; R = <sup><i>t</i></sup>Bu (HL<sup>1</sup>), Cy (HL<sup>2</sup>))
and iminophosphine (3,5-Me<sub>2</sub>Pz)<sub>2</sub>CHPÂ(R)<sub>2</sub>NAr (R = Cy, Ar = Ph (HL<sup>3</sup>); R = Ph, Ar = Ph (HL<sup>4</sup>), Ar = 2,6-Me<sub>2</sub>-phenyl
(HL<sup>5</sup>)) heteroscorpionate ligands were synthesized. Abstraction
of the methide proton of these ligands by rare-earth-metal trisÂ(alkyl)Âs,
LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(THF)<sub>2</sub>, afforded
the corresponding zwitterionic bisÂ(alkyl) complexes L<sup>1–5</sup>LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(THF) (L<sup>1</sup>, Ln = Y (<b>1a</b>), Lu (<b>1b</b>); L<sup>2</sup>,
Ln = Y (<b>2a</b>), Lu (<b>2b</b>); L<sup>3</sup>, Ln
= Y (<b>3a</b>), Lu (<b>3b</b>); L<sup>4</sup>, Ln = Y
(<b>4a</b>), Lu (<b>4b</b>); L<sup>5</sup>, Ln = Y (<b>5a</b>), Lu (<b>5b</b>), while metathesis reaction of the
lithium salts of LiL<sup>3</sup> and LiL<sup>4</sup> with YCl<sub>3</sub>(THF)<sub>2</sub> or YBr<sub>3</sub>(THF)<sub>2</sub> followed
by treatment with LiCH<sub>2</sub>SiMe<sub>3</sub> and KNÂ(SiHMe<sub>2</sub>)<sub>2</sub>, respectively, afforded the first heteroscorpionate
yttrium mixed halogen/alkyl or amido complexes L<sup>3–4</sup>YÂ(Cl)Â(CH<sub>2</sub>SiMe<sub>3</sub>)Â(THF) (L<sup>3</sup> (<b>6a</b>), L<sup>4</sup> (<b>7a</b>)), L<sup>3–4</sup>YÂ(Cl)Â(NÂ(SiHMe<sub>2</sub>)<sub>2</sub>)Â(THF) (L<sup>3 </sup>(<b>8a</b>), L<sup>4</sup> (<b>9a</b>)), L<sup>4</sup>YÂ(Br)Â(CH<sub>2</sub>SiMe<sub>3</sub>)Â(THF) (<b>10a</b>), and
L<sup>4</sup>YÂ(Br)Â(NÂ(SiHMe<sub>2</sub>)<sub>2</sub>)Â(THF) (<b>11a</b>). The structures of these complexes were well-defined, and the molecular
structures of <b>1a</b>, <b>2a</b>, <b>3b</b>, <b>4b</b>, <b>5a</b>, and <b>7a</b> were further characterized
by single crystal X-ray diffraction analysis. Complexes <b>1</b>–<b>5</b> showed similar high activity toward the ROP
of <i>rac</i>-LA at room temperature, and both the alkyl
species participated in initiation, of which the lutetium complexes
exhibited slightly higher selectivity than their yttrium analogues
(<i>P</i><sub>r</sub> = 0.85–0.89 vs 0.80–0.84)
despite the bulkiness of the ligands. Interestingly, the mixed halogen
complexes <b>6a</b>–<b>11a</b> were single-site
initiators, where the σ-halogen moiety remaining on the central
metal showed, for the first time, facilitating the heteroselectivity
up to <i>P</i><sub>r</sub> = 0.98. This result sheds new
light on designing specifically selective catalytic precursors
Yttrium Hydride Complex Bearing CpPN/Amidinate Heteroleptic Ligands: Synthesis, Structure, and Reactivity
The reaction of the yttrium dialkyls (C<sub>5</sub>H<sub>4</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)ÂYÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(thf) (<b>1</b>) with an excess
of <i>N</i>,<i>N′</i>-diisopropylcarbodiimide
gave
the yttrium monoalkyl complex (C<sub>5</sub>H<sub>4</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)ÂYÂ(CH<sub>2</sub>SiMe<sub>3</sub>)Â[<sup><i>i</i></sup>PrNî—»CÂ(CH<sub>2</sub>SiMe<sub>3</sub>)–N<sup><i>i</i></sup>Pr] (<b>2</b>). <b>2</b> subsequently
reacted with 1 equiv of PhSiH<sub>3</sub> to generate the CpPN/amidinate
heteroleptic yttrium hydride {(C<sub>5</sub>H<sub>4</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)ÂYÂ[<sup><i>i</i></sup>PrNî—»CÂ(CH<sub>2</sub>SiMe<sub>3</sub>)–N<sup><i>i</i></sup>Pr]Â(μ-H)}<sub>2</sub> (<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-bisÂ(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
η<sup>2</sup>-Cp bonding mode, yttrium terminal alkynyl complex <b>5</b>, yttrium η<sup>3</sup>-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 (C<sub>5</sub>H<sub>4</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)ÂYÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(thf) (<b>1</b>) with an excess
of <i>N</i>,<i>N′</i>-diisopropylcarbodiimide
gave
the yttrium monoalkyl complex (C<sub>5</sub>H<sub>4</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)ÂYÂ(CH<sub>2</sub>SiMe<sub>3</sub>)Â[<sup><i>i</i></sup>PrNî—»CÂ(CH<sub>2</sub>SiMe<sub>3</sub>)–N<sup><i>i</i></sup>Pr] (<b>2</b>). <b>2</b> subsequently
reacted with 1 equiv of PhSiH<sub>3</sub> to generate the CpPN/amidinate
heteroleptic yttrium hydride {(C<sub>5</sub>H<sub>4</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)ÂYÂ[<sup><i>i</i></sup>PrNî—»CÂ(CH<sub>2</sub>SiMe<sub>3</sub>)–N<sup><i>i</i></sup>Pr]Â(μ-H)}<sub>2</sub> (<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-bisÂ(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
η<sup>2</sup>-Cp bonding mode, yttrium terminal alkynyl complex <b>5</b>, yttrium η<sup>3</sup>-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 LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub> (Ln = Sc, Y, and Lu) with 1 equiv of CpPN-type
ligands C<sub>5</sub>H<sub>4</sub>PPh<sub>2</sub>–NH–C<sub>6</sub>H<sub>3</sub>R<sub>2</sub> (R = Me, <b>L<sup>1</sup>(Me)</b>; R = <sup><i>i</i></sup>Pr, <b>L<sup>1</sup>(<sup><i>i</i></sup>Pr)</b>) at room temperature readily generated
the corresponding CpPN-type bisÂ(alkyl) complexes <b>1</b> and <b>2a</b>–<b>2c</b>. Addition of 3 equiv of LiCH<sub>2</sub>SiMe<sub>3</sub> to a mixture of <b>L<sup>1</sup>(<sup><i>i</i></sup>Pr)</b> and LnCl<sub>3</sub>(thf)<sub>2</sub> (Ln = Sm and Nd) also afforded the CpPN-type bisÂ(alkyl) complexes <b>2d</b> and <b>2e</b>. The Cp moiety bonds to the central
metal in a classical η<sup>5</sup> mode in all CpPN-type complexes <b>1</b> and <b>2</b>. In contrast, the Cp<sup>Me</sup>PN-type
ligands C<sub>5</sub>Me<sub>4</sub>H–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub>R<sub>2</sub> (R = Me, <b>L<sup>2</sup>(Me)</b>; R = <sup><i>i</i></sup>Pr, <b>L<sup>2</sup>(<sup><i>i</i></sup>Pr)</b>) behaved differently. <b>L<sup>2</sup>(Me)</b> did not react with ScÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub>. Similarly, <b>L<sup>2</sup>(<sup><i>i</i></sup>Pr)</b> was also inert to ScÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub> even at 50 °C. When the
central metal was changed to yttrium, however, the equimolar reaction
between YÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub> and <b>L<sup>2</sup>(<sup><i>i</i></sup>Pr)</b> in
the presence of LiCl afforded two bisÂ(alkyl) complexes <b>3a</b> and <b>3b</b>. In the main product <b>3a</b>, [C<sub>5</sub>HMe<sub>3</sub>(η<sup>3</sup>-CH<sub>2</sub>)–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>]ÂYÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(thf), the ligand bonds to the Y<sup>3+</sup> ion in a rare η<sup>3</sup>-allyl/κ-N mode, whereas in <b>3b</b>, <b>(</b>C<sub>5</sub>Me<sub>4</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)ÂYÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(LiCl)Â(thf), the Cp ring coordinates
to the Y<sup>3+</sup> ion in an η<sup>5</sup> mode, and a LiCl
unit is located between the Y<sup>3+</sup> ion and the nitrogen atom.
When the central metal was changed to lutetium, a bisÂ(alkyl) complex <b>4a</b>, [C<sub>5</sub>HMe<sub>3</sub>(η<sup>3</sup>-CH<sub>2</sub>)–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>]ÂLuÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(thf), and a bisÂ(alkyl) complex <b>4b</b>, (C<sub>5</sub>Me<sub>4</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)ÂLuÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>, were isolated. The protonolysis
reaction of the IndPN-type ligands C<sub>9</sub>H<sub>7</sub>–PPh<sub>2</sub>N–C<sub>6</sub>H<sub>3</sub>R<sub>2</sub> (R
= Me, <b>L<sup>3</sup>(Me)</b>; R = Et, <b>L<sup>3</sup>(Et)</b>; R = <sup><i>i</i></sup>Pr, <b>L<sup>3</sup>(<sup><i>i</i></sup>Pr)</b>) with LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub> (Ln = Sc, Y, and Lu) generated the
IndPN-type bisÂ(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 η<sup>3</sup>-bonding
fashion. The more bulky FluPN-type ligands C<sub>13</sub>H<sub>9</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>4</sub>R (R = H, <b>L<sup>4</sup>(H)</b>; R = Me, <b>L<sup>4</sup>(Me)</b>) were treated with LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub> (Ln = Sc and Lu) to afford the FluPN-type
bisÂ(alkyl) complexes <b>8</b> and <b>9a</b> and <b>9b</b>, where the Flu moiety has a rare η<sup>1</sup>-bonding
mode. Complexes <b>1</b>–<b>9</b> were fully characterized
by <sup>1</sup>H, <sup>13</sup>C, and <sup>31</sup>P NMR; X-ray; and
elemental analyses. Upon activation with AlR<sub>3</sub> and [Ph<sub>3</sub>C]Â[BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>], 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 AlR<sub>3</sub>, 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 LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub> (Ln = Sc, Y, and Lu) with 1 equiv of CpPN-type
ligands C<sub>5</sub>H<sub>4</sub>PPh<sub>2</sub>–NH–C<sub>6</sub>H<sub>3</sub>R<sub>2</sub> (R = Me, <b>L<sup>1</sup>(Me)</b>; R = <sup><i>i</i></sup>Pr, <b>L<sup>1</sup>(<sup><i>i</i></sup>Pr)</b>) at room temperature readily generated
the corresponding CpPN-type bisÂ(alkyl) complexes <b>1</b> and <b>2a</b>–<b>2c</b>. Addition of 3 equiv of LiCH<sub>2</sub>SiMe<sub>3</sub> to a mixture of <b>L<sup>1</sup>(<sup><i>i</i></sup>Pr)</b> and LnCl<sub>3</sub>(thf)<sub>2</sub> (Ln = Sm and Nd) also afforded the CpPN-type bisÂ(alkyl) complexes <b>2d</b> and <b>2e</b>. The Cp moiety bonds to the central
metal in a classical η<sup>5</sup> mode in all CpPN-type complexes <b>1</b> and <b>2</b>. In contrast, the Cp<sup>Me</sup>PN-type
ligands C<sub>5</sub>Me<sub>4</sub>H–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub>R<sub>2</sub> (R = Me, <b>L<sup>2</sup>(Me)</b>; R = <sup><i>i</i></sup>Pr, <b>L<sup>2</sup>(<sup><i>i</i></sup>Pr)</b>) behaved differently. <b>L<sup>2</sup>(Me)</b> did not react with ScÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub>. Similarly, <b>L<sup>2</sup>(<sup><i>i</i></sup>Pr)</b> was also inert to ScÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub> even at 50 °C. When the
central metal was changed to yttrium, however, the equimolar reaction
between YÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub> and <b>L<sup>2</sup>(<sup><i>i</i></sup>Pr)</b> in
the presence of LiCl afforded two bisÂ(alkyl) complexes <b>3a</b> and <b>3b</b>. In the main product <b>3a</b>, [C<sub>5</sub>HMe<sub>3</sub>(η<sup>3</sup>-CH<sub>2</sub>)–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>]ÂYÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(thf), the ligand bonds to the Y<sup>3+</sup> ion in a rare η<sup>3</sup>-allyl/κ-N mode, whereas in <b>3b</b>, <b>(</b>C<sub>5</sub>Me<sub>4</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)ÂYÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(LiCl)Â(thf), the Cp ring coordinates
to the Y<sup>3+</sup> ion in an η<sup>5</sup> mode, and a LiCl
unit is located between the Y<sup>3+</sup> ion and the nitrogen atom.
When the central metal was changed to lutetium, a bisÂ(alkyl) complex <b>4a</b>, [C<sub>5</sub>HMe<sub>3</sub>(η<sup>3</sup>-CH<sub>2</sub>)–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>]ÂLuÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(thf), and a bisÂ(alkyl) complex <b>4b</b>, (C<sub>5</sub>Me<sub>4</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)ÂLuÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>, were isolated. The protonolysis
reaction of the IndPN-type ligands C<sub>9</sub>H<sub>7</sub>–PPh<sub>2</sub>N–C<sub>6</sub>H<sub>3</sub>R<sub>2</sub> (R
= Me, <b>L<sup>3</sup>(Me)</b>; R = Et, <b>L<sup>3</sup>(Et)</b>; R = <sup><i>i</i></sup>Pr, <b>L<sup>3</sup>(<sup><i>i</i></sup>Pr)</b>) with LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub> (Ln = Sc, Y, and Lu) generated the
IndPN-type bisÂ(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 η<sup>3</sup>-bonding
fashion. The more bulky FluPN-type ligands C<sub>13</sub>H<sub>9</sub>–PPh<sub>2</sub>î—»N–C<sub>6</sub>H<sub>4</sub>R (R = H, <b>L<sup>4</sup>(H)</b>; R = Me, <b>L<sup>4</sup>(Me)</b>) were treated with LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub>(thf)<sub>2</sub> (Ln = Sc and Lu) to afford the FluPN-type
bisÂ(alkyl) complexes <b>8</b> and <b>9a</b> and <b>9b</b>, where the Flu moiety has a rare η<sup>1</sup>-bonding
mode. Complexes <b>1</b>–<b>9</b> were fully characterized
by <sup>1</sup>H, <sup>13</sup>C, and <sup>31</sup>P NMR; X-ray; and
elemental analyses. Upon activation with AlR<sub>3</sub> and [Ph<sub>3</sub>C]Â[BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>], 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 AlR<sub>3</sub>, the polymerization temperature, and
the polymerization time on the catalytic activity were also discussed