C-centred chiral metal alkyls,

Michael F. Lappert; Colin L. Raston; Brian W. Skelton; Allan H. White

C-centred chiral metal alkyls,

Michael F. Lappert, Colin L. Raston, Brian W. Skelton, Allan H. White

Research output: Contribution to journal › Article › peer-review

10 Citations (Scopus)

Abstract

The chloro(alkyl)metallocenes [MR*(Cl)(η-C₅H₅)₂] [R* = ^-CH(SiMe₃)C₆H₄Me-o; M = Zr 1 or Hf 2] have been prepared from [MCl₂(η-C₅H₅)₂] and LiR*(tmen) (tmen = N,N,N′,N′-tetramethylethane-1,2-diamine); further alkylation occurred only for M = Zr, affording rac-3a and meso-3b, [ZrR*₂(η-C₅H₅)₂]. In contrast, reaction of 2 equivalents of Li[CH(SiMe₃)₂](tmen) with [ZrCl₂(η-C₅H₅)₂] yielded an alkyl elimination product possessing μ-η¹:η⁵-C⁵H₄^2- ligands. Compound 1 was reversibly reduced (E_1/2^red = -1.72 V vs. saturated calomel electrode, SCE) whereas 2, 3a or 3b were irreversibly reduced (E^red = -2.12, -2.08, -2.00 V respectively vs. SCE). Thermolysis of 3b in toluene gave 3a (80°C) or 'Zr(C₁₀H₈)' (120°C). Photolysis of 3a or 3b at 20°C in tetrahydrofuran (thf) yielded a 1:1 mixture of 3a and 3b; a d¹ intermediate has been unambiguously identified as [ZrR*(η-C₅H₅)₂]. Reduction of 1 (Na-Hg), or 3a and 3b (Na[C₁₀H₈]), in thf also gave [ZrR*(η-C₅H₅)₂] but this slowly transformed into [ZrR*(η-C₅H₅)₂(thf)], and 1 with Na[C₁₀H₈] and PPh₃ gave [ZrR*(η-C₅H₅)₂(PPh₃)]. Reduction of 1, 3a or 3b, or photolysis of 3a or 3b, in the presence of PMe₃ gave [ZrR*(η-C₅H₅)₂(PMe₃)]. Crystal structure determinations showed a slightly more crowded metal environment in 2 than in 1, consistent with the view that dialkylation in 2 is limited on steric grounds; M-σ-C 2.359(4) (1), 2.322(8) (2), metal-centroid 2.22 (1), 2.21 (2), M-Cl 2.444(1) (1), 2.418(3) (2) Å. The structure of 3a confirms the rac assignment, M-σ-C 2.37₄ Å, metal-centroid 2.23, 2.24 Å.

Original language	English
Pages (from-to)	2895-2902
Number of pages	8
Journal	Journal of the Chemical Society - Dalton Transactions
Issue number	17
Publication status	Published - 7 Sep 1997
Externally published	Yes

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@article{d334700378824ed4a3d5dba3c1a92228,

title = "C-centred chiral metal alkyls,",

abstract = "The chloro(alkyl)metallocenes [MR*(Cl)(η-C5H5)2] [R* = -CH(SiMe3)C6H4Me-o; M = Zr 1 or Hf 2] have been prepared from [MCl2(η-C5H5)2] and LiR*(tmen) (tmen = N,N,N′,N′-tetramethylethane-1,2-diamine); further alkylation occurred only for M = Zr, affording rac-3a and meso-3b, [ZrR*2(η-C5H5)2]. In contrast, reaction of 2 equivalents of Li[CH(SiMe3)2](tmen) with [ZrCl2(η-C5H5)2] yielded an alkyl elimination product possessing μ-η1:η5-C5H42- ligands. Compound 1 was reversibly reduced (E1/2red = -1.72 V vs. saturated calomel electrode, SCE) whereas 2, 3a or 3b were irreversibly reduced (Ered = -2.12, -2.08, -2.00 V respectively vs. SCE). Thermolysis of 3b in toluene gave 3a (80°C) or 'Zr(C10H8)' (120°C). Photolysis of 3a or 3b at 20°C in tetrahydrofuran (thf) yielded a 1:1 mixture of 3a and 3b; a d1 intermediate has been unambiguously identified as [ZrR*(η-C5H5)2]. Reduction of 1 (Na-Hg), or 3a and 3b (Na[C10H8]), in thf also gave [ZrR*(η-C5H5)2] but this slowly transformed into [ZrR*(η-C5H5)2(thf)], and 1 with Na[C10H8] and PPh3 gave [ZrR*(η-C5H5)2(PPh3)]. Reduction of 1, 3a or 3b, or photolysis of 3a or 3b, in the presence of PMe3 gave [ZrR*(η-C5H5)2(PMe3)]. Crystal structure determinations showed a slightly more crowded metal environment in 2 than in 1, consistent with the view that dialkylation in 2 is limited on steric grounds; M-σ-C 2.359(4) (1), 2.322(8) (2), metal-centroid 2.22 (1), 2.21 (2), M-Cl 2.444(1) (1), 2.418(3) (2) {\AA}. The structure of 3a confirms the rac assignment, M-σ-C 2.374 {\AA}, metal-centroid 2.23, 2.24 {\AA}.",

author = "Lappert, {Michael F.} and Raston, {Colin L.} and Skelton, {Brian W.} and White, {Allan H.}",

year = "1997",

month = sep,

day = "7",

language = "English",

pages = "2895--2902",

journal = "Journal of the Chemical Society, Dalton Transactions",

issn = "1470-479X",

number = "17",

}

TY - JOUR

T1 - C-centred chiral metal alkyls,

AU - Lappert, Michael F.

AU - Raston, Colin L.

AU - Skelton, Brian W.

AU - White, Allan H.

PY - 1997/9/7

Y1 - 1997/9/7

N2 - The chloro(alkyl)metallocenes [MR*(Cl)(η-C5H5)2] [R* = -CH(SiMe3)C6H4Me-o; M = Zr 1 or Hf 2] have been prepared from [MCl2(η-C5H5)2] and LiR*(tmen) (tmen = N,N,N′,N′-tetramethylethane-1,2-diamine); further alkylation occurred only for M = Zr, affording rac-3a and meso-3b, [ZrR*2(η-C5H5)2]. In contrast, reaction of 2 equivalents of Li[CH(SiMe3)2](tmen) with [ZrCl2(η-C5H5)2] yielded an alkyl elimination product possessing μ-η1:η5-C5H42- ligands. Compound 1 was reversibly reduced (E1/2red = -1.72 V vs. saturated calomel electrode, SCE) whereas 2, 3a or 3b were irreversibly reduced (Ered = -2.12, -2.08, -2.00 V respectively vs. SCE). Thermolysis of 3b in toluene gave 3a (80°C) or 'Zr(C10H8)' (120°C). Photolysis of 3a or 3b at 20°C in tetrahydrofuran (thf) yielded a 1:1 mixture of 3a and 3b; a d1 intermediate has been unambiguously identified as [ZrR*(η-C5H5)2]. Reduction of 1 (Na-Hg), or 3a and 3b (Na[C10H8]), in thf also gave [ZrR*(η-C5H5)2] but this slowly transformed into [ZrR*(η-C5H5)2(thf)], and 1 with Na[C10H8] and PPh3 gave [ZrR*(η-C5H5)2(PPh3)]. Reduction of 1, 3a or 3b, or photolysis of 3a or 3b, in the presence of PMe3 gave [ZrR*(η-C5H5)2(PMe3)]. Crystal structure determinations showed a slightly more crowded metal environment in 2 than in 1, consistent with the view that dialkylation in 2 is limited on steric grounds; M-σ-C 2.359(4) (1), 2.322(8) (2), metal-centroid 2.22 (1), 2.21 (2), M-Cl 2.444(1) (1), 2.418(3) (2) Å. The structure of 3a confirms the rac assignment, M-σ-C 2.374 Å, metal-centroid 2.23, 2.24 Å.

AB - The chloro(alkyl)metallocenes [MR*(Cl)(η-C5H5)2] [R* = -CH(SiMe3)C6H4Me-o; M = Zr 1 or Hf 2] have been prepared from [MCl2(η-C5H5)2] and LiR*(tmen) (tmen = N,N,N′,N′-tetramethylethane-1,2-diamine); further alkylation occurred only for M = Zr, affording rac-3a and meso-3b, [ZrR*2(η-C5H5)2]. In contrast, reaction of 2 equivalents of Li[CH(SiMe3)2](tmen) with [ZrCl2(η-C5H5)2] yielded an alkyl elimination product possessing μ-η1:η5-C5H42- ligands. Compound 1 was reversibly reduced (E1/2red = -1.72 V vs. saturated calomel electrode, SCE) whereas 2, 3a or 3b were irreversibly reduced (Ered = -2.12, -2.08, -2.00 V respectively vs. SCE). Thermolysis of 3b in toluene gave 3a (80°C) or 'Zr(C10H8)' (120°C). Photolysis of 3a or 3b at 20°C in tetrahydrofuran (thf) yielded a 1:1 mixture of 3a and 3b; a d1 intermediate has been unambiguously identified as [ZrR*(η-C5H5)2]. Reduction of 1 (Na-Hg), or 3a and 3b (Na[C10H8]), in thf also gave [ZrR*(η-C5H5)2] but this slowly transformed into [ZrR*(η-C5H5)2(thf)], and 1 with Na[C10H8] and PPh3 gave [ZrR*(η-C5H5)2(PPh3)]. Reduction of 1, 3a or 3b, or photolysis of 3a or 3b, in the presence of PMe3 gave [ZrR*(η-C5H5)2(PMe3)]. Crystal structure determinations showed a slightly more crowded metal environment in 2 than in 1, consistent with the view that dialkylation in 2 is limited on steric grounds; M-σ-C 2.359(4) (1), 2.322(8) (2), metal-centroid 2.22 (1), 2.21 (2), M-Cl 2.444(1) (1), 2.418(3) (2) Å. The structure of 3a confirms the rac assignment, M-σ-C 2.374 Å, metal-centroid 2.23, 2.24 Å.

UR - http://www.scopus.com/inward/record.url?scp=33748598452&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:33748598452

SP - 2895

EP - 2902

JO - Journal of the Chemical Society, Dalton Transactions

JF - Journal of the Chemical Society, Dalton Transactions

SN - 1470-479X

IS - 17

ER -

C-centred chiral metal alkyls,

Abstract

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