Organoosmium(VI) complexes of PMe(3), PPh(3), and Ph(2)PCH(2)CH(2)PPh(2) (dppe) have been prepared and characterized. Unlike inorganic complexes of nitridoosmium(VI), the alkyl complexes are not reduced by basic phosphines. The reactions of [NBu(4)] [Os(N)(CH(2)SiMe(3))(4)] with HBF4 in the presence of either PMe(3) or PPh(3) produces Os(N)(CH2- SiMe(3))(3)(PR(3)). The addition of either PMe(3) or dppe to [NBu(4)] [Os(N)(CH(2)SiMe(3))(2)Cl-2] produces Os(N)(CH2-SiMe(3))(2)L(2)Cl (L = PMe(3), 1/2 dppe). Abstraction of the chloride ligand in Os(N)(CH(2)SiMe(3))(2)L(2)Cl with [Ag-(NCMe)(4)][BF4] gives [Os(N) (CH(2)SiMe(3))(2)L(2)(NCMe)] [BF4]. In the absence of acetonitrile, [Os(N)(CH(2)SiMe(3))(2)L(2)] [BF4] forms. The molecular structure of [Os(N) (CH(2)SiMe(3))(2)(dppe)(NCMe)][BF4] was determined by X-ray diffraction. Crystals are monoclinic in space group P2(1)/a with a = 17.544(7) Angstrom A, b = 12.269(5) Angstrom A, c =20.666(4) Angstrom A, alpha = gamma = 90 degrees, beta = 104.76(3)degrees, Z = 4, R = 0.036, and R(w) = 0.038.