Structure and Reactivity of Trimethylsilylmethyl Complexes of Chromium, Including the 13-Electron Alkyl CpCr(CH2SiMe3)2

Alkylation of Cp*Cr(THF)Cl2 with 1 or 2 equiv of LiCH2SiMe3 yielded the paramagnetic chromium alkyls [Cp*Cr(μ-Cl)(CH2SiMe3)]2 (1), Cp*Cr(CH2SiMe3)2 (2), and Cp*Cr(L)(CH2SiMe3)2 (3a, L = py; 3b, L = THF). Compound 2 is a coordinatively unsaturated, pseudo-five-coordinate CrIII complex with a 13-elect...

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Published inOrganometallics Vol. 17; no. 25; pp. 5477 - 5485
Main Authors Heintz, Robert A, Leelasubcharoen, Somying, Liable-Sands, Louise M, Rheingold, Arnold L, Theopold, Klaus H
Format Journal Article
LanguageEnglish
Published American Chemical Society 07.12.1998
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Summary:Alkylation of Cp*Cr(THF)Cl2 with 1 or 2 equiv of LiCH2SiMe3 yielded the paramagnetic chromium alkyls [Cp*Cr(μ-Cl)(CH2SiMe3)]2 (1), Cp*Cr(CH2SiMe3)2 (2), and Cp*Cr(L)(CH2SiMe3)2 (3a, L = py; 3b, L = THF). Compound 2 is a coordinatively unsaturated, pseudo-five-coordinate CrIII complex with a 13-electron configuration, and it catalyzes the polymerization of ethylene. The thermal decomposition of 2 in noncoordinating solvents proceeded via an intermediate, namely the bis(μ-alkylidene) complex [Cp*Cr(μ-CHSi(CH3)3)]2 (4). Compound 4 suffered reductive elimination to yield the dinuclear CrII alkyl Cp*2Cr2(μ-CH2Si(CH3)2CH2-μ-CHSi(CH3)3) (5). In contrast, the decomposition of 2 in THF, i.e., 3b, yielded the metallacycles Cp*Cr(L)(CH2)2Si(CH3)3) (6a, L = py; 6b, L = THF). Compounds 1, 2, 3b, 4, and 5 have been structurally characterized by X-ray diffraction. The reactions of 2 are rationalized in terms of competing α- and γ-hydrogen elimination processes yielding terminal alkylidene and metallacyclobutane intermediates existing in equilibrium.
Bibliography:istex:8752E8291C5240B2C47B88FCD2077DD447513C5D
ark:/67375/TPS-XSZG8CS0-8
ISSN:0276-7333
1520-6041
DOI:10.1021/om980796z