TY - JOUR
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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U2 - 10.1039/a806099a
DO - 10.1039/a806099a
M3 - Article
AN - SCOPUS:33748469525
SN - 0300-9246
SP - 147
EP - 154
JO - Journal of the Chemical Society - Dalton Transactions
JF - Journal of the Chemical Society - Dalton Transactions
IS - 2
ER -