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2.1.8.2.1 Preparation of Tetraalkylmanganate(II)

DOI: 10.1055/sos-SD-002-00002

Oshima, K.Science of Synthesis, (2003240.

The formation of alkylmanganese(II) complexes by the interaction of manganese(II) halides with alkylating reagents was first reported by Gilman, but the organometallic products were neither isolated nor characterized.[‌61‌,‌62‌] Later, Tamura and Kochi compared the rates of decomposition of alkylmanganese(II) complexes prepared in situ by the action of Grignard reagents on manganese(II) chloride in tetrahydrofuran.[‌63‌] Shortly thereafter, the synthesis and characterization of several β-stabilized organomanganese species of the type [(MnR2)n], such as monomeric bis[tris(trimethylsilyl)methyl]manganese(II),[‌64‌] dimeric bis[bis(2-methyl-2-phenylpropyl)manganese(II)],[‌65‌] and trimeric tris[dimesitylmanga­nese(II)][‌66‌] were reported. In 1976, Wilkinson reported that the interaction of diethyl ether suspensions of anhydrous manganese(II) chloride with 4 equivalents of methyl­lithium followed by the addition of N,N,N,N-tetramethylethylenediamine gives the lithium tetramethylmanganate(II)bis(N,N,N,N-tetramethylethylenediamine) salt (Li2MnMe42TMEDA) (cf. Scheme 42),[‌65‌] whose EPR spectrum has been determined. Morris and Girolami reported single-crystal X-ray analyses of [Li(TMEDA)]2[MnR14] (R1=Me, Et, CH2CH2-t-Bu)} (Scheme 42).[‌67‌] These 13-electron peralkyl species are stable at room temperature and are among the few well-characterized compounds of their type. The alkyls that contain β-hydrogen atoms are remarkably resistant to β-elimination. For instance, crystalline samples of lithiumN,N,N,N-tetramethylethylenediamine tetraethylmanganate(II) are remarkably robust and may be heated under argon to 110°C before noticeable decomposition occurs. The compounds [Li(TMEDA)]2[MnR14] (R1=Et, CH2CH2-t-Bu) are the first structurally characterized transition-metal peralkyls that contain β-hydrogen atoms.

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