Synthesis, DFT Studies, and Reactions of Scandium and Yttrium Dialkyl Cations Containing Neutral <i>fac</i>-N₃ and <i>fac</i>-S₃ Donor Ligands

Reaction of Sc(CH2SiMe3)3(THF)2 with 1,4,7-trithiacyclononane gave Sc([9]aneS3)(CH2SiMe3)3, the first organometallic group 3 complex of [9]aneS3 ([9]aneS3 = 1,4,7-trithiacyclononane). The corresponding reaction for yttrium gave equilibrium mixtures of Y([9]aneS3)(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]aneS3)R3 with those for the previously reported fac-N3 donor complexes M(fac-N3)R3 (R = Me or CH2SiMe3; fac-N3 = 1,4,7-trimethyltriazacyclononane (Me3[9]aneN3) or HC(Me2pz)3). Reaction of M(CH2SiMe3)3(THF)2 with [NHMe2Ph][BArF4] (ArF = C6F5) in the presence of a face-capping ligand L (L = HC(Me2pz)3, Me3[9]aneN3, or [9]aneS3) 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 29Si NMR spectroscopy and/or DFT and found to possess β-Si−C agostic alkyl groups in most instances. The isolated cations [Sc(fac-N3)(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 = HC(Me2pz)3, Me3[9]aneN3, or [9]aneS3 and R = CH2SiMe3 when activated with 1 equiv of [CPh3][BArF4]. When activated with 2 equiv of [CPh3][BArF4], the compounds were also very active for the polymerization of 1-hexene

Synthesis, DFT Studies, and Reactions of Scandium and Yttrium Dialkyl Cations Containing Neutral <i>fac</i>-N₃ and <i>fac</i>-S₃ Donor Ligands

Reaction of Sc(CH2SiMe3)3(THF)2 with 1,4,7-trithiacyclononane gave Sc([9]aneS3)(CH2SiMe3)3, the first organometallic group 3 complex of [9]aneS3 ([9]aneS3 = 1,4,7-trithiacyclononane). The corresponding reaction for yttrium gave equilibrium mixtures of Y([9]aneS3)(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]aneS3)R3 with those for the previously reported fac-N3 donor complexes M(fac-N3)R3 (R = Me or CH2SiMe3; fac-N3 = 1,4,7-trimethyltriazacyclononane (Me3[9]aneN3) or HC(Me2pz)3). Reaction of M(CH2SiMe3)3(THF)2 with [NHMe2Ph][BArF4] (ArF = C6F5) in the presence of a face-capping ligand L (L = HC(Me2pz)3, Me3[9]aneN3, or [9]aneS3) 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 29Si NMR spectroscopy and/or DFT and found to possess β-Si−C agostic alkyl groups in most instances. The isolated cations [Sc(fac-N3)(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 = HC(Me2pz)3, Me3[9]aneN3, or [9]aneS3 and R = CH2SiMe3 when activated with 1 equiv of [CPh3][BArF4]. When activated with 2 equiv of [CPh3][BArF4], the compounds were also very active for the polymerization of 1-hexene

A Family of Scandium and Yttrium Tris((trimethylsilyl)methyl) Complexes with Neutral N₃ Donor Ligands

The first group 3 organometallic compounds containing the tris(3,5-dimethylpyrazolyl)methane (HC(Me2pz)3) and 1,3,5-trimethyltriazacyclohexane (Me3[6]aneN3) ligands are reported, together with the homologous 1,4,7-triazacyclononane-supported compounds and trichloride derivatives for many of the ligands. Reaction of M(CH2SiMe3)3(THF)2 (M = Sc, Y) with Me3[9]aneN3 (1,4,7-trimethyltriazacyclononane), HC(Me2pz)3, or Me3[6]aneN3 gave the corresponding tris((trimethylsilyl)methyl) derivatives M(Me3[9]aneN3)(CH2SiMe3)3 (M = Sc (1), Y (2)), M{HC(Me2pz)3}(CH2SiMe3)3 (M = Sc (3), Y (4)), and M(Me3[6]aneN3)(CH2SiMe3)3 (M = Sc (12), Y (13)). Reaction of 3 with 2,6-dimethylphenol (ArOH) gave the tris(aryloxide) derivative Sc{HC(Me2pz)3}(OAr)3 (9), and reaction of HC(Me2pz)3 with MCl3 gave M{HC(Me2pz)3}Cl3 (M = Sc (5), Y(6)). Attempts to prepare tris((trimethylsilyl)methyl) complexes with the more sterically demanding tris(3-R-pyrazolyl)methanes (R = iPr, Ph, tBu) or the related tris(pyrazolyl)methylsilane ligand were unsuccessful. However, the trichlorides M{HC(iPrpz)3}Cl3 (M = Sc (7), Y (8)) and M{MeSi(Me2pz)3}Cl3 (M = Sc (10), Y (11)) could be made. In related studies the reaction of ScCl3(THF)3 with Me3[6]aneN3 afforded Sc(Me3[6]aneN3)Cl3 (14), but the yttrium congener could not be prepared. The compounds 1, 3, 4, 9, 11, and 14 have been crystallographically characterized. Competitive ligand exchange reactions for the tris(alkyl) compounds M(L)(CH2SiMe3)3 established the binding preference L = Me3[9]aneN3 > Me3[6]aneN3 > HC(Me2pz)3 for M = Sc and L = Me3[9]aneN3 > HC(Me2pz)3 > Me3[6]aneN3 for M = Y. Reaction of ScR3(THF)2 (R = CH2SiMe3, Ph) with 1-(3,5-di-tert-butyl-2-hydroxybenzyl)-4,7-dimethyltriazacyclononane (HL1) or 1-(3,5-di-tert-butyl-2-hydroxybenzyl)-4,7-diisopropyltriazacyclononane (HL2) gave organoscandium derivatives of mono(phenoxy)-substituted triazacyclononane ligands, namely Sc(L1)R2 (R = CH2SiMe3 (15), Ph (17)) and Sc(L2)(CH2SiMe3)2 (16). Reaction of 15 with 2 equiv of TolOH (Tol = p-tolyl) afforded Sc(L1)(OTol)2 (18), which was crystallographically characterized