SYNTHESIS AND CHARACTERIZATION OF VOLATILE MONOMERIC COPPER(II) FLUOROALKOXIDES

The reaction of [Cu(OMe)2]n with a fluorinated alcohol in the presence of an amine has afforded a series of new copper(II) fluoroalkoxides: Cu(hfip)2(tMed) (2), Cu(hfip)2(teed) (3), Cu(hfip)2(bipy) (4), Cu(hfip)2(py) (5), Cu(hftb)2(tMed) (6), Cu(hftb)2(bipy) (7), and Cu(hftb)2(py)2 (8), where hfip = hexafluoroisopropoxo, hftb = hexafluoro-tert-butoxo, tmed = N,N,N',N'-tetramethylethylenediamine, teed = N,N,N',N'-tetraethylethylenediamine, bipy = bipyridine, and py = pyridine. Compounds 5 and 8 have also been prepared by the reaction of CuBr2 with Na(hfip) or Na(hftb) and pyridine. Crystallographic analyses of 2 and 6 reveal that both compounds are monomeric and assume tetrahedrally-distorted square-planar geometries. The dihedral angles between the CuN2 and CuO2 planes are 16. 1-degrees for 2 and 40.6-degrees for 6. The average Cu-O distances are 1.903 (3) angstrom in 2 and 1.884 (3) angstrom in 6, and the average Cu-N distances are 2.035 (5) angstrom in 2 and 2.064 (3) angstrom in 6. EPR and UV-vis studies indicate that the degree of distortion increases in the order 4 < 2 < 3 < 7 < 5 < 6 < 8. The increase in the degree of distortion is attributed to the greater steric crowding in the latter molecules. Interestingly, these compounds are relatively resistant to hydrolysis: aqueous solutions of 2 are stable in air at room temperature and hydrolyze to copper(II) oxide only when the solutions are refluxed. Compounds 2, 3, 4, 6, and 7 are volatile, and thus are potential metal-organic chemical vapor deposition (MOCVD) precursors. Sublimation of 2 and passage of the resulting vapor over substrates heated to 300-degrees-C result in the deposition of copper metal. These deposits are noncrystalline and consist of granules having diameters of O.1-0.4 mum. Crystal data: for Cu(hfip)2(tmed)(2), space group P2(1)/c, monoclinic, a = 9.454 (1) angstrom, b = 15.045 (2) angstrom, c = 14.197 (6) angstrom, beta = 105.65 (2)-degrees, V = 1944 (1) angstrom3, Z = 4, R(F) = 0.040 and R(wF) = 0.052 for 334 variables and 2060 data; for Cu(hftb)2(tmed) (6), space group I2/a, monoclinic, a = 13.601 (3) angstrom, b = 9.567 (2) angstrom, c = 16.562 (5) angstrom, beta = 106.56 (2)-degrees, V = 2066 (2) angstrom3, Z = 4, R(F) = 0.043 and R(wF) = 0.037 for 190 variables and 1427 data.