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)(2)L (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)0 from the basal plane. This distortion seems to reduce sigma* 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)-(xH(2)O) precursor. The deposition rate of copper oxide film on a Pt layer above 450degreesC 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) Angstrom, b = 18.0831(10) Angstrom, c = 12.8864(11) Angstrom, beta = 111.839(5)degrees , monoclinic, space group P2(1)/c, Z = 4.