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^′=Bu^t, 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^′=Bu^t) 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.