1357445-28-3Relevant articles and documents
Titanium(IV) trifluoromethyl complexes: New perspectives on bonding from organometallic fluorocarbon chemistry
Taw, Felicia L.,Clark, Aurora E.,Mueller, Alexander H.,Janicke, Michael T.,Cantat, Thibault,Scott, Brian L.,Hay, P. Jeffrey,Hughes, Russell P.,Kiplinger, Jaqueline L.
, p. 1484 - 1499 (2012)
Trifluoromethyltrimethylsilane, (CH3)3SiCF 3, in the presence of CsF serves as an excellent CF3 group-transfer reagent, and reaction with Cp2TiF2 in THF gives the titanocene trifluoromethyl fluoride complex Cp2Ti(CF 3)(F) (1; Cp = C5H5) in 60% isolated yield. Reaction of complex 1 with the trimethylsilyl reagents, (CH3) 3SiX (X = OTf = OSO2CF3, Cl, Br, I, N 3, and OSO2Ph), in a tetrahydrofuran or toluene solution affords the corresponding Ti-CF3 derivatives Cp2Ti(CF 3)(X) (X = OTf (2), Cl (12), Br (13), I (14), N3 (15), and OSO2Ph (16)) in good isolated yields of 67-84%. These compounds have been characterized by a combination of reactivity studies, IR and 1H/13C{1H}/19F NMR spectroscopies, and single-crystal X-ray diffraction. The Ti-CF3 linkage in these complexes is remarkably robust, and although the α-C-F bonds are elongated, there is no evidence of an α-fluoride (Ti???F- CF2) between the electrophilic Ti(IV) metal center and any of the C-F bonds in the trifluoromethyl group in the solid-state or in solution. In the solid-state, these complexes are shock-sensitive; energetic decomposition of Cp2Ti(CF3)(F) (1) produces uniform spherical nanoparticles ranging from ～70 to 120 nm in size and porous fluorinated oligomers and polymers containing both -(CF2-CF2)- and -(CF 2-CFH)- units, as determined by a combination of SEM, XRD, XRF, XPS, and 19F MAS NMR. Density functional theory results show good agreement with experimental structural data obtained for Cp 2Ti(CF3)(X) (X = F (1), OTf (2), Cl (12), N3 (15)) and accurately predicts longer Ti-CF3 distances than for each specific CH3 analogue, and the trend extends to structurally related Zr and Hf analogues. Simpler model compounds from groups 4 and 8 (M(CH 3)4, M(CH3)3(CF3), M(CH3)3(CCl3), and M(CH3) 3(CF2CF2CF2CF3); M = Ti, Zr, Hf, Fe, Ru, Os)) were also examined and show that, for group 4 complexes, π-bonding is a significant factor in shortening the strongly ionic M-CH 3 relative to M-CF3, whereas for the predominantly covalent group 8 analogues, π-back-bonding helps to shorten the predominantly covalent M-CF3 relative to M-CH3. The bonding analysis suggests that the significant elongation of C-F bonds α to metals is mainly a consequence of the electropositivity of the group 4 metal centers, with minor, if any, contributions from π-effects; the bond-lengthening effect is most pronounced at the α-position and decays rapidly on moving away from the metal.
