Highly reactive organolanthanides. Systematic routes to and olefin chemistry of early and late bis(pentamethylcyclopentadienyl) 4f hydrocarbyl and hydride complexes

Gerald Jeske, Harald Lauke, Heiko Mauermann, Paul N. Swepston, Herbert Schumann, Tobin J Marks

Research output: Contribution to journalArticle

541 Citations (Scopus)

Abstract

The reaction of the organolanthanide complexes Cp′2MCl2-Li(ether)2 +, Cp′ = η'-(CH3)5C5, M = La, Nd, Sm, and Lu, with LiCH[Si(CH3)3]2 provides a straightforward route to the broad class of ether- and halide-free bis(pentamethylcyclopentadienyl) lanthanide alkyls, Cp′2MCH[Si(CH3)3]2. These complexes were characterized by standard analytical methodology. The M = Nd complex crystallizes in the monoclinic space group P21/n with four molecules in a cell of dimensions (-100°C) a = 11.045 (9) Å, b = 23.554 (7) Å, c = 11.648 (9) Å, and β = 103.10 (6)°. Least-squares refinement led to a value for the conventional R index (on F) of 0.078 for 4287 independent, absorption-corrected reflections having I > 3σ(I). The molecular structure consists of monomeric Cp′2NdCH[Si(CH3)3]2 units with a "bent-sandwich" Cp′2Nd configuration: (ring centroid)-Nd-(ring centroid) = 134.4°. The CH[Si(CH3)3]2 fragment is coordinated to the Cp′2Nd group in a highly unsymmetrical fashion with a Nd-C σ-bond distance of 2.517 (7) Å and a rather short secondary contact to a single methyl carbon atom of 2.895 (7) Å. Spectroscopic data suggest that this interaction is higly metal-to-carbon in character. The Cp′2NdCH[Si(CH3)3]2 complexes react with H2 under mild conditions to yield the corresponding hydrides (Cp′2MH)2. These complexes are extremely active homogeneous ethylene polymerization catalysts with turnover frequencies exceeding 1800 s-1 (25°C, 1 atm of ethylene pressure) for M = La. Activities are in the order La ≥ Nd ≫ Lu. The kinetics of this process and the molecular weight characteristics of the resulting polymer are severely limited by mass transport effects; evidence is presented that these are "living" polymers and that chain transfer by β-hydride elimination is not important. For La and Nd, propylene and 1-hexene react rapidly at -10°C to yield equal quantities of the disproportionation products alkane + metal η3-alkenyl. Butadiene undergoes reaction with these hydrides to yield η3-crotyl complexes, and significant polymerization does not occur. For 1-hexene under low H2 (or D2) pressure at room temperature, some formation of 2-methylundecane is also observed. The analogous reaction of cyclohexene with these hydrides is sluggish and appears to produce an η1-cyclohexenyl complex. There is no evidence for cyclohexene oligomers. Although unreactive toward olefins, Cp′2NdCH[Si(CH3)3]2 reacts with CO to yield a dimeric dionediolate.

Original languageEnglish
Pages (from-to)8091-8103
Number of pages13
JournalJournal of the American Chemical Society
Volume107
Issue number26
Publication statusPublished - 1985

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Alkenes
Hydrides
Polymerization
Ether
Olefins
Polymers
Carbon
Metals
Pressure
Lanthanoid Series Elements
Alkanes
Carbon Monoxide
Molecular Structure
Least-Squares Analysis
Ethers
Ethylene
Molecular Weight
Temperature
Rare earth elements
Butadiene

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Highly reactive organolanthanides. Systematic routes to and olefin chemistry of early and late bis(pentamethylcyclopentadienyl) 4f hydrocarbyl and hydride complexes. / Jeske, Gerald; Lauke, Harald; Mauermann, Heiko; Swepston, Paul N.; Schumann, Herbert; Marks, Tobin J.

In: Journal of the American Chemical Society, Vol. 107, No. 26, 1985, p. 8091-8103.

Research output: Contribution to journalArticle

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abstract = "The reaction of the organolanthanide complexes Cp′2MCl2-Li(ether)2 +, Cp′ = η'-(CH3)5C5, M = La, Nd, Sm, and Lu, with LiCH[Si(CH3)3]2 provides a straightforward route to the broad class of ether- and halide-free bis(pentamethylcyclopentadienyl) lanthanide alkyls, Cp′2MCH[Si(CH3)3]2. These complexes were characterized by standard analytical methodology. The M = Nd complex crystallizes in the monoclinic space group P21/n with four molecules in a cell of dimensions (-100°C) a = 11.045 (9) {\AA}, b = 23.554 (7) {\AA}, c = 11.648 (9) {\AA}, and β = 103.10 (6)°. Least-squares refinement led to a value for the conventional R index (on F) of 0.078 for 4287 independent, absorption-corrected reflections having I > 3σ(I). The molecular structure consists of monomeric Cp′2NdCH[Si(CH3)3]2 units with a {"}bent-sandwich{"} Cp′2Nd configuration: (ring centroid)-Nd-(ring centroid) = 134.4°. The CH[Si(CH3)3]2 fragment is coordinated to the Cp′2Nd group in a highly unsymmetrical fashion with a Nd-C σ-bond distance of 2.517 (7) {\AA} and a rather short secondary contact to a single methyl carbon atom of 2.895 (7) {\AA}. Spectroscopic data suggest that this interaction is higly metal-to-carbon in character. The Cp′2NdCH[Si(CH3)3]2 complexes react with H2 under mild conditions to yield the corresponding hydrides (Cp′2MH)2. These complexes are extremely active homogeneous ethylene polymerization catalysts with turnover frequencies exceeding 1800 s-1 (25°C, 1 atm of ethylene pressure) for M = La. Activities are in the order La ≥ Nd ≫ Lu. The kinetics of this process and the molecular weight characteristics of the resulting polymer are severely limited by mass transport effects; evidence is presented that these are {"}living{"} polymers and that chain transfer by β-hydride elimination is not important. For La and Nd, propylene and 1-hexene react rapidly at -10°C to yield equal quantities of the disproportionation products alkane + metal η3-alkenyl. Butadiene undergoes reaction with these hydrides to yield η3-crotyl complexes, and significant polymerization does not occur. For 1-hexene under low H2 (or D2) pressure at room temperature, some formation of 2-methylundecane is also observed. The analogous reaction of cyclohexene with these hydrides is sluggish and appears to produce an η1-cyclohexenyl complex. There is no evidence for cyclohexene oligomers. Although unreactive toward olefins, Cp′2NdCH[Si(CH3)3]2 reacts with CO to yield a dimeric dionediolate.",
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TY - JOUR

T1 - Highly reactive organolanthanides. Systematic routes to and olefin chemistry of early and late bis(pentamethylcyclopentadienyl) 4f hydrocarbyl and hydride complexes

AU - Jeske, Gerald

AU - Lauke, Harald

AU - Mauermann, Heiko

AU - Swepston, Paul N.

AU - Schumann, Herbert

AU - Marks, Tobin J

PY - 1985

Y1 - 1985

N2 - The reaction of the organolanthanide complexes Cp′2MCl2-Li(ether)2 +, Cp′ = η'-(CH3)5C5, M = La, Nd, Sm, and Lu, with LiCH[Si(CH3)3]2 provides a straightforward route to the broad class of ether- and halide-free bis(pentamethylcyclopentadienyl) lanthanide alkyls, Cp′2MCH[Si(CH3)3]2. These complexes were characterized by standard analytical methodology. The M = Nd complex crystallizes in the monoclinic space group P21/n with four molecules in a cell of dimensions (-100°C) a = 11.045 (9) Å, b = 23.554 (7) Å, c = 11.648 (9) Å, and β = 103.10 (6)°. Least-squares refinement led to a value for the conventional R index (on F) of 0.078 for 4287 independent, absorption-corrected reflections having I > 3σ(I). The molecular structure consists of monomeric Cp′2NdCH[Si(CH3)3]2 units with a "bent-sandwich" Cp′2Nd configuration: (ring centroid)-Nd-(ring centroid) = 134.4°. The CH[Si(CH3)3]2 fragment is coordinated to the Cp′2Nd group in a highly unsymmetrical fashion with a Nd-C σ-bond distance of 2.517 (7) Å and a rather short secondary contact to a single methyl carbon atom of 2.895 (7) Å. Spectroscopic data suggest that this interaction is higly metal-to-carbon in character. The Cp′2NdCH[Si(CH3)3]2 complexes react with H2 under mild conditions to yield the corresponding hydrides (Cp′2MH)2. These complexes are extremely active homogeneous ethylene polymerization catalysts with turnover frequencies exceeding 1800 s-1 (25°C, 1 atm of ethylene pressure) for M = La. Activities are in the order La ≥ Nd ≫ Lu. The kinetics of this process and the molecular weight characteristics of the resulting polymer are severely limited by mass transport effects; evidence is presented that these are "living" polymers and that chain transfer by β-hydride elimination is not important. For La and Nd, propylene and 1-hexene react rapidly at -10°C to yield equal quantities of the disproportionation products alkane + metal η3-alkenyl. Butadiene undergoes reaction with these hydrides to yield η3-crotyl complexes, and significant polymerization does not occur. For 1-hexene under low H2 (or D2) pressure at room temperature, some formation of 2-methylundecane is also observed. The analogous reaction of cyclohexene with these hydrides is sluggish and appears to produce an η1-cyclohexenyl complex. There is no evidence for cyclohexene oligomers. Although unreactive toward olefins, Cp′2NdCH[Si(CH3)3]2 reacts with CO to yield a dimeric dionediolate.

AB - The reaction of the organolanthanide complexes Cp′2MCl2-Li(ether)2 +, Cp′ = η'-(CH3)5C5, M = La, Nd, Sm, and Lu, with LiCH[Si(CH3)3]2 provides a straightforward route to the broad class of ether- and halide-free bis(pentamethylcyclopentadienyl) lanthanide alkyls, Cp′2MCH[Si(CH3)3]2. These complexes were characterized by standard analytical methodology. The M = Nd complex crystallizes in the monoclinic space group P21/n with four molecules in a cell of dimensions (-100°C) a = 11.045 (9) Å, b = 23.554 (7) Å, c = 11.648 (9) Å, and β = 103.10 (6)°. Least-squares refinement led to a value for the conventional R index (on F) of 0.078 for 4287 independent, absorption-corrected reflections having I > 3σ(I). The molecular structure consists of monomeric Cp′2NdCH[Si(CH3)3]2 units with a "bent-sandwich" Cp′2Nd configuration: (ring centroid)-Nd-(ring centroid) = 134.4°. The CH[Si(CH3)3]2 fragment is coordinated to the Cp′2Nd group in a highly unsymmetrical fashion with a Nd-C σ-bond distance of 2.517 (7) Å and a rather short secondary contact to a single methyl carbon atom of 2.895 (7) Å. Spectroscopic data suggest that this interaction is higly metal-to-carbon in character. The Cp′2NdCH[Si(CH3)3]2 complexes react with H2 under mild conditions to yield the corresponding hydrides (Cp′2MH)2. These complexes are extremely active homogeneous ethylene polymerization catalysts with turnover frequencies exceeding 1800 s-1 (25°C, 1 atm of ethylene pressure) for M = La. Activities are in the order La ≥ Nd ≫ Lu. The kinetics of this process and the molecular weight characteristics of the resulting polymer are severely limited by mass transport effects; evidence is presented that these are "living" polymers and that chain transfer by β-hydride elimination is not important. For La and Nd, propylene and 1-hexene react rapidly at -10°C to yield equal quantities of the disproportionation products alkane + metal η3-alkenyl. Butadiene undergoes reaction with these hydrides to yield η3-crotyl complexes, and significant polymerization does not occur. For 1-hexene under low H2 (or D2) pressure at room temperature, some formation of 2-methylundecane is also observed. The analogous reaction of cyclohexene with these hydrides is sluggish and appears to produce an η1-cyclohexenyl complex. There is no evidence for cyclohexene oligomers. Although unreactive toward olefins, Cp′2NdCH[Si(CH3)3]2 reacts with CO to yield a dimeric dionediolate.

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