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Abstract

Coordination of the new fluorous diamino-dialkoxy tetradentate ligands [OC(CF₃)₂CH₂N(Me)(CH₂)_nN(Me)C(CF₃)₂O]^2- (n = 2, [ON²NO]^2-; n = 3, [ON³NO]^2-) onto group 3 and group 4 metals has been studied. The diamino-diols [ONⁿNO]H₂ (n = 2, 1a; n = 3, 1b), prepared by ring-opening of (CF₃)₂COCH₂ with the corresponding secondary diamine, react cleanly with Ti(OiPr)₄ to yield quantitatively the dialkoxy complexes [ONⁿNO]Ti(OiPr)₂ (n = 2, 2a; n = 3, 2b). The chloride displacement reaction between TiCl₄ and 1a in the presence of NEt₃ leads to the dichlorotitanium complex [ON²NO]TiCl₂ (3). Alkane elimination and amine elimination reactions provide efficient routes to the zirconium and yttrium complexes [ON²NO]Zr(CH₂Ph)₂ (4), [ON²NO]Y(N(SiHMe₂)₂)(THF) (5), and [ON²NO]Y(CH₂SiMe₃)(THF) (6). X-ray crystallographic analyses show that in the solid state 3 and 4 adopt a distorted octahedral structure with a trans-O, cis-N, cis-X ligand (X = Cl, CH₂Ph). Solution NMR data for 2−4 are consistent with this C-symmetric structure. Variable-temperature NMR studies establish that 4 undergoes inversion of metal configuration (i.e., Λ/Δ isomerization, racemization) on the NMR time scale at elevated temperatures (ΔG⧧(racemization) = 17.0(1) kcal/mol). An X-ray crystallographic analysis reveals that 6 adopts in the solid state a seven-coordinate, distorted structure due to Y···F coordination to one of the four CF₃ substituents (Y−F = 2.806(2) Å). In contrast, NMR studies show that 6 adopts a C₂-symmetric structure in solution analogous to those of 2−4, while 5 features a C₁-symmetric structure.