Coordination Polyhedron and Chemical Vapor Deposition of Cu(hfacac)₂(<i>t</i>-BuNH₂)

A new pentacoordinate Cu(II) complex, Cu(hfacac)2(t-BuNH2) [hfacac = CF3C(O)CHC(O)CF3-, t-BuNH2 = tert-butylamine], has been synthesized and structurally characterized. Interestingly, the structure of a single crystal occurred as square pyramidal with one O atom at the apical position and one N and three O atoms at the basal positions, showing a serious degree of distortion. This contrasts with the square-pyramidal structure of Cu(hfacac)2L (L = H2O and pyrazine), which has the L ligand at the axial position. In the Cu(hfacac)2(t-BuNH2) complex, the t-BuNH2 ligand is placed at an equatorial position with a lowered angle by 19.9(2)° from the basal plane. This distortion seems to reduce σ* influence and steric hindrance and so stabilizes the square-pyramidal geometry. This precursor has a lower melting point and superior stability to air, moisture, and heat than the Cu(hfacac)2(xH2O) precursor. The deposition rate of copper oxide film on a Pt layer above 450 °C was nearly constant with increasing temperature, indicating a mass transport limited reaction. Therefore it would be a useful metal organic chemical vapor deposition precursor for the fabrication of copper oxide film or superconducting materials. Crystal data for Cu(hfacac)2(t-BuNH2): 293(2) K, a = 9.6699(4) Å, b = 18.0831(10) Å, c = 12.8864(11) Å, β = 111.839(5)°, monoclinic, space group P21/c, Z = 4.