Synthesis and structures of some new types of lithium β-diketiminates

Abstract

The tetracyclic dilithio-Si,Si′-oxo-bridged bis(N,N′-methylsilyl-β-diketiminates) 2 and 3, having an outer macrocycle, were prepared from [Li{CH(SiMe₃)SiMe(OMe)₂}]_∞ and 2 PhCN. They differ in that the substituent at the β-C atom of each diketiminato ligand is either SiMe₃ (2) or H (3). Each of 2 and 3 has (i) a central Si–O–Si unit, (ii) an Si(Me) fragment N,N′-intramolecularly bridging each β-diketiminate, and (iii) an Li(thf)₂ moiety N,N′-intermolecularly bridging the two β-diketiminates (thf = tetrahydrofuran). Treatment of [Li{CH(SiMe₃)(SiMe₂OMe)}]₈ with 2Me₂C(CN)₂ yielded the amorphous [Li{Si(Me)₂((NCR)₂CH)}]_n [R = C(Me)₂CN] (4). From [Li{N(SiMe₃)C(Bu^t)C(H)SiMe₃}]₂ (A) and 1,3- or 1,4-C₆H₄(CN)₂, with no apparent synergy between the two CN groups, the product was the appropriate (µ-C₆H₄)-bis(lithium β-diketiminate) 6 or 7. Reaction of [Li{N(SiMe₃)C(Ph)C(H)SiMe₃}(tmeda)] and 1,3-C₆H₄(CN)₂ afforded 1,3-C₆H₄(X)X′ (X = ; X′ = (9). Interaction of A and 2[1,2-C₆H₄(CN)₂] gave the bis(lithio-isoindoline) derivative (5). The X-ray structures of 2, 3, 5 and 9 are presented, and reaction pathways for each reaction are suggested.