Synthesis and thermal reactivity of organoscandium and yttrium complexes of sterically less bulky salicylaldiminato ligands

摘要

Scandium and yttribum bis (ligand) mono (alkyl) complexes, of N-phenyl (L~1)N-2-isopropylphenyl (L~2) and N-mesityl (L~3) substituted ortho-tert-butylsalicylaldiminato lgiands were rpepared by alkane elimination from [M(CH_2SiMe_2R)_3-(THF)_2] (R = Me, Ph) and two equivalents of proteo ligand (HL). The resulting [L_2M(THF)_n(CH_2SiMe_2R)] (n = 0-2), L = L~1 (1), L~2(2), L~3(3)) complexes are thermally unstable, decomposing rapidly between -20 and 20 deg C. In order to gain insight in to ligant features necessary to imaprt thermal stability in early transition metal organometallic chemistry, the decomposition pathways of 1-3 have been investigateda nd compared with more sterically congested N-2,6-diisopropylphenyl substituted analogues. Compounds 1 and 2 decompose rapidly and cleanly at room temperature by 1,3-migration of the entire CH_2SiMe_2R group to the aldiminecarobn. By contrast, L~3 mono(alkyls) 3 decompose cleanly by metallation of an ortho-C_6H_2Me_3 group. In the case of yttrium, the metallated alkyl undergoes subsequent 1,3-migration of the aldimine carbon, forming a five-membered C_4N-ring.