The stable silylene Si[(NCH2tBu)2C6H4-1,2]: insertion into LiC or LiSi bonds of lithium alkyls LiR or [LiSi(SiMe3)3(THF)3] [R=Me, tBu or CH(SiMe3)2]

The new crystalline amino-functionalised lithium silyls Li[Si{(NCH2tBu)2C6H4-1,2}R](L) [R=Si(SiMe3)3 (sisyl), L=(THF)2 (2); R=Me, L=(OEt2)2 (3); R=tBu, L=(THF)3 (4a) or THF(OEt2) (4b); R=CH(SiMe3)2, L=(THF)2 (5)] have been obtained in high yield from the silylene Si[(NCH2tBu)2C6H4-1,2] and LiR under mild conditions. A by-product in the reaction leading to 4 was the crystalline disilane [1,2-C6H4(NCH2tBu)2(tBu)Si]2 (6). Each of 2–6 was fully characterised by microanalysis, multinuclear NMR spectra and X-ray structures. Each of the compounds 3–6 was thermally stable in solution, whereas the sisyl derivative 2 retained its integrity only at low temperatures, being completely dissociated into its factors at ambient temperature.