Synthesis and crystal structures of novel lithium- and palladium-1-azaallyls

Treatment of (RH2C)2C5H3N-2,6 (R=SiMe3) with BunLi followed by addition of Me3SiCl gave the tetrasilyl pyridine derivative (R2HC)2C5H3N-2,6 1 in high yield. Further lithiation of 1 with BunLi and reaction of the intermediate with PhCN led to the new lithium-1-azaallyl [Li{N(R)C(Ph)C(R)(C5H3N-2,6)(CHR2)}]22, while metallation of the previously described di-lithium compounds [Li{N(R)C(R′)CH}2(C5H3-2,6)]Li(tmen)n (R=SiMe3, R′=But, n=1 or R=SiMe3, R′=Ph, n=2) with PdCl2(PhCN)2 yielded the novel metallacycles [Pd{{N(H)(R)C(R′)CH}{N(SiMe2CH2)C(R′)CH}C5H3N-2,6}] 3 (R′=But) and [Pd{{N(R)C(R′)CH}{N(R)(H)C(R′)CH}C5H3N-2,6}2] (R′=Ph) 4 in moderate to low yield. Compound 3 is unusual in being the first example of a crystallographically characterised PdNSiC heterocycle which is believed to be formed via an intramolecular CH-activation of a trimethylsilyl group by Pd(II). All four compounds were fully characterised by NMR-spectroscopy, microanalysis (not 4) and X-ray diffraction.