C2-symmetiric fluorous diamino-dialkoxide complexes of early transition metals

Coordination of the new fluorous diamino-dialkoxy tetradentate ligands [OC(CF3)(2)CH2N(Me)(CH2)(n)N(Me)C(CF3)(2) O](2-) (n = 2, [ON2 NO](2-); n = 3, [(ONNO)-N-3](2-)) onto group 3 and group 4 metals has been studied. The diamino-diols [(ONNO)-N-n]H-2 (n = 2, 1a; n = 3, 1b), prepared by ring-opening of (CF3)(2)COCH2 with the corresponding secondary diamine, react cleanly with Ti(OiPr)(4) to yield quantitatively the dialkoxy complexes [(ONNO)-N-n]Ti(OiPr)(2) (n = 2, 2a; n = 3, 2b). The chloride displacement reaction between TiC1(4) and 1a in the presence of NEt3 leads to the dichlorotitanium complex [(ONNO)-N-2]TiCl2 (3). Alkane elimination and amine elimination reactions provide efficient routes to the zirconium and yttrium complexes [ON2- NO]Zr(CH2Ph)(2) (4), [(ONNO)-N-2]Y(N(SiHMe2)(2))(THF) (5), and [(ONNO)-N-2]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-2-symmetric structure. Variable-temperature NMR studies establish that 4 undergoes inversion of metal configuration (i.e., Delta/Delta isomerization, racemization) on the NMR time scale at elevated temperatures (DeltaG(double dagger)(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 (YF)-F-... coordination to one of the four CF3 substituents (Y-F = 2.806(2) A). In contrast, NMR studies show that 6 adopts a C2-symmetric structure in solution analogous to those of 2-4, while 5 features a Cl-symmetric structure.