Chemistry of 2,3-dihydro-2-metallaphenalenes. Part 1. Synthesis of CHRSiMe₂CHR′C₁₀H₆ (R = R′ = H; R = R′ = SiMe₃; And R,R′ = H,SiMe₃) and formation of the compound: [{Li(Me2NCH2CH2NMe2)} 2{CHRSiMe2C(SiMe3)C10H6 via Decomposition of [{Li(Me2NCH2CH2NMe2)} 2{1,8-(CHSiMe3)2C10H6}]; Crystal structures of two polymorphs of the silicon heterocycle dilithium complex

The complexes [{Li(tmen)}₂{1,8-(CHSiMe₃)₂C₁₀H ₆}] (9) (tmen = NNN′N′-tetramethylethylenediamine) and [{Li(tmen)}{CHSiMe₂CH₂C₁₀H₆}] (13) have been prepared via metallation of species formed by in situ Grignard trapping reactions of 1,8-(ClCH₂)₂C₁₀H₆ with SiMe₃Cl and SiMe₂Cl₂ respectively; synthesis of the siline, meso-CH(SiMe₃)SiMe₂CH(SiMe₃)C ₁₀H₆ from (9) is also described. In hexane, (9) decomposes to [{Li(tmen)}₂{CHSiMe₂C(SiMe₃)C ₁₀H₆ (10) to yield the compound CH₂SiMe₂CH(SiMe₃)C₁₀H₆ on the addition of aqueous HCl, the same product as that obtained from a reaction of (13) with SiMe₃Cl. The nature of (10) has been established by X-ray structure determination of two polymorphs, α and β, which differ both in the mode of interaction of the Li(tmen)⁺ moieties with the carbanion [η⁶:η³ (α), cf. η⁴:η³ (β)] and the conformation of the heterocyclic ring.