Synthesis, DFT Studies, and Reactions of Scandium and Yttrium Dialkyl Cations Containing Neutral fac-N3 and fac-S3 Donor Ligands
摘要:
Reaction of Sc(CH2SiMe3)(3)(THF)(2) with 1,4,7-trithiacyclononane gave Sc([9]aneS(3))(CH2SiMe3)(3), the first organometallic group 3 complex of [9]aneS(3) ([9]aneS(3) = 1,4,7-trithiacyclononane). The corresponding reaction for yttrium gave equilibrium mixtures of Y([9]aneS(3))(CH2SiMe3)(3) and starting materials. Density functional theory (DFT) was used to compare the energies of formation and metal-ligand interaction energies for M([9]aneS(3))R-3 with those for the previously reported fac-N-3 donor complexes M(fac-N-3)R-3 (R = Me or CH2SiMe3; fac-N-3 = 1,4,7-trimethyltriazacyclononane (Me-3[9]aneN(3)) or HC(Me(2)pz)(3)). Reaction of M(CH2SiMe3)(3)(THF)(2) with [NHMe2Ph][BAr4F] (Ar-F = C6F5) in the presence of a facecapping ligand L (L = HC(Me(2)pz)(3), Me-3[9]aneN(3), or [9]aneS(3)) gave the cationic complexes [M(L)(CH2SiMe3)2(THF)](+), which has been structurally characterized for M = Sc and L = [9]aneS3. The corresponding base-free cations [M(L)(CH2SiMe3)(2)](+) were studied by Si-29 NMR spectroscopy and/or DFT and found to possess beta-Si-C agostic alkyl groups in most instances. The isolated cations [Sc(fac-N-3)(CH2SiMe3)(2)(THF)](+) underwent THF substitution reactions with OPPh3 or pyridine, Sc-alkyl migratory insertion with carbodiimides, and C-H bond metathesis with PhCCH. The olefin polymerization capabilities of a series of complexes M(L)R3 have been determined. The scandium complexes were found to be very productive for ethylene polymerization for L (L = HC(Me(2)pz)(3), Me-3[9]aneN(3), or [9]aneS(3) and R = CH2SiMe3 when activated with 1 equiv of [CPh3][BAr4F]. When activated with 2 equiv of [CPh3][BAr4F], the compounds were also very active for the polymerization of 1-hexene.