One-electron oxidation of paramagnetic chromium(II) alkyl complexes with alkyl halides: Synthesis and structure of five-coordinate chromium(III) complexes

Michael D. Fryzuk; Daniel B. Leznoff; Steven J. Rettig; Victor G. Young

doi:10.1039/a806099a

One-electron oxidation of paramagnetic chromium(II) alkyl complexes with alkyl halides: Synthesis and structure of five-coordinate chromium(III) complexes

Michael D. Fryzuk, Daniel B. Leznoff, Steven J. Rettig, Victor G. Young

Chemistry (Twin Cities)

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

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Abstract

The reaction of square-planar, high-spin CrR[N(SiMe₂CH₂PPh₂)₂] (R = Me, CH₂SiMe₃) with alkyl halides (MeI, CF₃CH₂I, MeBr, PhCH₂Cl) generates one-electron oxidation products Cr(R)X[N(SiMe₂CH₂PPh₂)₂], unusual examples of five-coordinate chromium(III) complexes. Cr(Me)Br[N(SiMe₂CH₂PPh₂)₂] and Cr(CH₂SiMe₃)Cl[N-(SiMe₂CH₂PPh ₂)₂] have been structurally characterized. Alkylation of the latter complex with LiCH₂SiMe₃ gave a five-coordinate Cr(III) dialkyl complex Cr(CH₂SiMe₃)₂[N(SiMe₂CH ₂PPh₂)₂], which was structurally characterized as well. Attempts to isolate sterically unencumbered Cr(III) dialkyl (e.g., dimethyl) complexes resulted in decomposition. Addition of an excess of PhCH₂Cl to {[(Ph₂PCH₂SiMe₂)₂N]Cr} ₂(μ-Cl)₂ resulted in halide-transfer to form CrCl₂(THF)[N(SiMe₂CH₂PPh₂) ₂] in low yield. Reaction of the low-spin CrCp[N(SiMe₂CH₂PPh₂)₂] complex with PhCH₂Cl, however, gave both Cr(Cp)(CH₂Ph)[N(SiMe₂CH₂PPh₂) ₂] and Cr(Cp)Cl[N(SiMe₂CH₂PPh₂)₂]. The five-coordinate Cr(III) alkyl halide complexes do not polymerize ethylene at 60°C and 1 atm; the dialkyl complex Cr(CH₂SiMe₃)₂[N(SiMe₂CH ₂PPh₂)₂] does catalyze polyethylene formation but is quickly deactivated. A discussion comparing the structural distortions observed in these five-coordinate high-spin d³ Cr(III) complexes with those observed in the analogous low-spin d⁶ Ir(III) complexes is presented.

Original language	English (US)
Pages (from-to)	147-154
Number of pages	8
Journal	Journal of the Chemical Society - Dalton Transactions
Issue number	2
DOIs	https://doi.org/10.1039/a806099a
State	Published - Jan 21 1999

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One-electron oxidation of paramagnetic chromium(II) alkyl complexes with alkyl halides : Synthesis and structure of five-coordinate chromium(III) complexes. / Fryzuk, Michael D.; Leznoff, Daniel B.; Rettig, Steven J.; Young, Victor G.

In: Journal of the Chemical Society - Dalton Transactions, No. 2, 21.01.1999, p. 147-154.

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

@article{749e183e643644dcb624c3c764bde55c,

title = "One-electron oxidation of paramagnetic chromium(II) alkyl complexes with alkyl halides: Synthesis and structure of five-coordinate chromium(III) complexes",

abstract = "The reaction of square-planar, high-spin CrR[N(SiMe2CH2PPh2)2] (R = Me, CH2SiMe3) with alkyl halides (MeI, CF3CH2I, MeBr, PhCH2Cl) generates one-electron oxidation products Cr(R)X[N(SiMe2CH2PPh2)2], unusual examples of five-coordinate chromium(III) complexes. Cr(Me)Br[N(SiMe2CH2PPh2)2] and Cr(CH2SiMe3)Cl[N-(SiMe2CH2PPh 2)2] have been structurally characterized. Alkylation of the latter complex with LiCH2SiMe3 gave a five-coordinate Cr(III) dialkyl complex Cr(CH2SiMe3)2[N(SiMe2CH 2PPh2)2], which was structurally characterized as well. Attempts to isolate sterically unencumbered Cr(III) dialkyl (e.g., dimethyl) complexes resulted in decomposition. Addition of an excess of PhCH2Cl to {[(Ph2PCH2SiMe2)2N]Cr} 2(μ-Cl)2 resulted in halide-transfer to form CrCl2(THF)[N(SiMe2CH2PPh2) 2] in low yield. Reaction of the low-spin CrCp[N(SiMe2CH2PPh2)2] complex with PhCH2Cl, however, gave both Cr(Cp)(CH2Ph)[N(SiMe2CH2PPh2) 2] and Cr(Cp)Cl[N(SiMe2CH2PPh2)2]. The five-coordinate Cr(III) alkyl halide complexes do not polymerize ethylene at 60°C and 1 atm; the dialkyl complex Cr(CH2SiMe3)2[N(SiMe2CH 2PPh2)2] does catalyze polyethylene formation but is quickly deactivated. A discussion comparing the structural distortions observed in these five-coordinate high-spin d3 Cr(III) complexes with those observed in the analogous low-spin d6 Ir(III) complexes is presented.",

author = "Fryzuk, {Michael D.} and Leznoff, {Daniel B.} and Rettig, {Steven J.} and Young, {Victor G.}",

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T1 - One-electron oxidation of paramagnetic chromium(II) alkyl complexes with alkyl halides

T2 - Synthesis and structure of five-coordinate chromium(III) complexes

AU - Fryzuk, Michael D.

AU - Leznoff, Daniel B.

AU - Rettig, Steven J.

AU - Young, Victor G.

PY - 1999/1/21

Y1 - 1999/1/21

N2 - The reaction of square-planar, high-spin CrR[N(SiMe2CH2PPh2)2] (R = Me, CH2SiMe3) with alkyl halides (MeI, CF3CH2I, MeBr, PhCH2Cl) generates one-electron oxidation products Cr(R)X[N(SiMe2CH2PPh2)2], unusual examples of five-coordinate chromium(III) complexes. Cr(Me)Br[N(SiMe2CH2PPh2)2] and Cr(CH2SiMe3)Cl[N-(SiMe2CH2PPh 2)2] have been structurally characterized. Alkylation of the latter complex with LiCH2SiMe3 gave a five-coordinate Cr(III) dialkyl complex Cr(CH2SiMe3)2[N(SiMe2CH 2PPh2)2], which was structurally characterized as well. Attempts to isolate sterically unencumbered Cr(III) dialkyl (e.g., dimethyl) complexes resulted in decomposition. Addition of an excess of PhCH2Cl to {[(Ph2PCH2SiMe2)2N]Cr} 2(μ-Cl)2 resulted in halide-transfer to form CrCl2(THF)[N(SiMe2CH2PPh2) 2] in low yield. Reaction of the low-spin CrCp[N(SiMe2CH2PPh2)2] complex with PhCH2Cl, however, gave both Cr(Cp)(CH2Ph)[N(SiMe2CH2PPh2) 2] and Cr(Cp)Cl[N(SiMe2CH2PPh2)2]. The five-coordinate Cr(III) alkyl halide complexes do not polymerize ethylene at 60°C and 1 atm; the dialkyl complex Cr(CH2SiMe3)2[N(SiMe2CH 2PPh2)2] does catalyze polyethylene formation but is quickly deactivated. A discussion comparing the structural distortions observed in these five-coordinate high-spin d3 Cr(III) complexes with those observed in the analogous low-spin d6 Ir(III) complexes is presented.

AB - The reaction of square-planar, high-spin CrR[N(SiMe2CH2PPh2)2] (R = Me, CH2SiMe3) with alkyl halides (MeI, CF3CH2I, MeBr, PhCH2Cl) generates one-electron oxidation products Cr(R)X[N(SiMe2CH2PPh2)2], unusual examples of five-coordinate chromium(III) complexes. Cr(Me)Br[N(SiMe2CH2PPh2)2] and Cr(CH2SiMe3)Cl[N-(SiMe2CH2PPh 2)2] have been structurally characterized. Alkylation of the latter complex with LiCH2SiMe3 gave a five-coordinate Cr(III) dialkyl complex Cr(CH2SiMe3)2[N(SiMe2CH 2PPh2)2], which was structurally characterized as well. Attempts to isolate sterically unencumbered Cr(III) dialkyl (e.g., dimethyl) complexes resulted in decomposition. Addition of an excess of PhCH2Cl to {[(Ph2PCH2SiMe2)2N]Cr} 2(μ-Cl)2 resulted in halide-transfer to form CrCl2(THF)[N(SiMe2CH2PPh2) 2] in low yield. Reaction of the low-spin CrCp[N(SiMe2CH2PPh2)2] complex with PhCH2Cl, however, gave both Cr(Cp)(CH2Ph)[N(SiMe2CH2PPh2) 2] and Cr(Cp)Cl[N(SiMe2CH2PPh2)2]. The five-coordinate Cr(III) alkyl halide complexes do not polymerize ethylene at 60°C and 1 atm; the dialkyl complex Cr(CH2SiMe3)2[N(SiMe2CH 2PPh2)2] does catalyze polyethylene formation but is quickly deactivated. A discussion comparing the structural distortions observed in these five-coordinate high-spin d3 Cr(III) complexes with those observed in the analogous low-spin d6 Ir(III) complexes is presented.

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One-electron oxidation of paramagnetic chromium(II) alkyl complexes with alkyl halides: Synthesis and structure of five-coordinate chromium(III) complexes

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