PREPARATION OF TITANIUM FLUOROALKOXIDES BY ALCOHOLYSIS OF TITANIUM ALKOXIDES

Reaction of Ti(OR)(4) where R = i-Pr and Et with >4 equiv of fluoroalcohols, HOR(f) [R(f) = CH(CF3)(2), C6F5, 2,6-F2C6H3, 2,4-F2C6H3, 4-FC6H4, C6H5], results in the formation of a series of Ti(OR(f))(x)(OR)(4-x)(HOR)(n) compounds where x = 2-4 and n = 0 or 1. Only in the cases of R(f) = CH(CF3)(2) (x = 2) and 2,6-F2C6H3 (x = 2 and 3) does n = 0. The degree of substitution can be correlated to the electron-withdrawing ability of the R(f) group, with highly electron-withdrawing groups disfavoring complete substitution. These compounds have been characterized by combustion elemental analysis and infrared and H-1 and F-19 NMR spectroscopies. Single-crystal X-ray diffraction studies of Ti(OR(f))(x)(OR)(4-x)(HOR) [R(f) = CH(CF3)(2), R = Et, and x = 2; R(f) = C6F5, R = i-Pr, and x = 3], revealed centrosymmetric dinuclear structures held together by bridging oxygen atoms. The coordination geometries approximate edge-shared bioctahedra with the coordinated alcohols hydrogen-bonding across the dinuclear unit to an oxygen atom of an alkoxide. Crystal data for [Ti{OCH(CF3)(2)}(2)(OEt)(2)(HOEt)](2) at 25 degrees C: a 10.233(3) Angstrom, b = 12.702(4) Angstrom, c 16.175(7) Angstrom, beta 96.05(3)degrees, Z = 2, d(calc) 1.646 g cm(-3), space group P2(1)/n, R(F) 0.074, and R(wF) = 0.076. Crystal data for [Ti(OC6F5)3(O-i-Pr)(HO-i-Pr)](2). C7H8 at 25 degrees C: a 11.1009(9) Angstrom, b = 19.388(1) Angstrom, c = 14.397(1) Angstrom, beta = 92.805(6)degrees, Z = 2, d(calc) = 1.636 g cm(-3), space group P2(1)/n, R(F) = 0.0773, and R(wF) = 0.0879. The X-ray crystal structure of [Ti(O-2,6-F2C6H3)3 (O-i-Pr)](2) has also been determined. The coordination geometry defined by the oxygen atoms of the alkoxide ligands approximates a square-based pyramid, with an isopropoxide in the apical site [Ti(1)-O(4) = 1.718(6) Angstrom and Ti(1)-O(4)-C(4) = 159.6(6)degrees]. One of the terminal phenoxides has a nearly linear angle [169.3(6)degrees], while the other has a relatively acute angle [123.3(4)degrees]. The phenyl group of the latter is oriented such that a fluorine fills the site trans to the isopropoxide. Ti(1)-F(1) = 2.704(5) Angstrom is virtually identical to the sum of the van der Waals radii of fluorine and Ti(IV). Crystal data at 25 degrees C: a = 11.4404(9) Angstrom, b = 18.927(2) Angstrom, c = 10.830(1) Angstrom, beta = 114.968(7)degrees, Z = 2, d(calc) = 1.541 g cm(-3), space group P2(1)/c, R(F) = 0.0564 and R(wF) = 0.0573. The two compounds that do not coordinate alcohol [R = i-Pr; R(f) = 2,6-F2C6H3, x = 3, and R(f) = CH(CF3)(2), x = 2], also do not form stable complexes with Lewis bases such as acetonitrile or THF. This contrasts with Ti[OCH(CF3)(2)](4), which forms volatile Ti[OCH(CF3)(2)](4)L(2) [L = MeC=N and THF] compounds. The structure of Ti[OCH(CF3)(2)](4)(N=CMe)(2) has been determined using X-ray crystallography. The nitrile ligands occupy cis positions in the distorted octahedral coordination geometry. Crystal data for at 25 degrees C: a 10.2872(7) Angstrom, b = 15.295(1) Angstrom, c 18.651(1) Angstrom, Z = 4, d(calc) = 1.811 g cm(-3), space group C222(1), R(F) = 0.0583, and R(wF) = 0.0550.