Treatment of titanium tetrachloride (2 equiv) with dimethyl diselenide or diethyl diselenide (1 equiv) in hexane at 0 degrees C, followed by crystallization at -20 degrees C, afforded (TiCl(4))(2)(Se(2)(CH(3))(2)) (78%) and (TiCl(4))(2)(Se(2)(CH(2)CH(3))(2)) (63%), respectively, as red and orange crystalline solids. (TiCl(4))(2)(Se(2)(CH(2)CH(3))(2)) is stable in solution and in the solid state at 23 degrees C, but (TiCl(4))(2)(Se(2)(CH(3))(2)) decomposes to TiCl(4)(Se(CH(3))(2))(2), gray selenium, and other products upon standing in hexane solution, in the solid state, or upon sublimation at 250 degrees C. Treatment of titanium tetrachloride with 2 equiv of dimethyl selenide or diethyl selenide in hexane at ambient temperature afforded a spectroscopically pure brick red solid of TiCl(4)(Se(CH(3))(2))(2) (96%) or TiCl(4)(Se(CH(2)CH(3))(2))(2) (96%), respectively. X-ray crystal structures of (TiCl(4))(2)(Se(2)(CH(2)CH(3))(2)), TiCl(4)(Se(CH(3))(2))(2), and TiCl(4)(Se(CH(2)CH(3))(2))(2) were determined to establish solid state nuclearities. (TiCl(4))(2)(Se(2)(CH(2)CH(3))(2)) crystallizes in the hexagonal space group P3(1)21 with a = 12.106(1) Å, c = 10.786(1) Å, V = 1368.8(4) Å(3), and Z = 3. TiCl(4)(Se(CH(3))(2))(2) crystallizes in the monoclinic space group P2(1)/n with a = 8.175(1) Å, b = 13.051(1) Å, c = 16.871(3) Å, beta = 102.675(8) degrees, V = 1756.3(2) Å(3), and Z = 4. TiCl(4)(Se(CH(2)CH(3))(2))(2) crystallizes in the monoclinic space group P2(1)/n with a = 6.404(4) Å, b = 16.376(7) Å, c = 13.058(8) Å, beta = 101.45(4) degrees, V = 1342(1) Å(3), and Z = 4. TiCl(4)(Se(CH(3))(2))(2) and TiCl(4)(Se(CH(2)CH(3))(2))(2) were evaluated as precursors to titanium diselenide films. TiCl(4)(Se(CH(3))(2))(2) was not a good precursor, but TiCl(4)(Se(CH(2)CH(3))(2))(2) afforded rose-bronze colored titanium diselenide films at substrate temperatures of 500-600 degrees C. The films were characterized by X-ray powder diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Surprisingly, titanium diselenide films prepared from TiCl(4)(Se(CH(2)CH(3))(2))(2) are moisture sensitive and are apparently hydrolyzed by ambient moisture to titanium dioxide and hydrogen selenide. The relevance of the coordination chemistry to the development of precursors to titanium diselenide films is discussed.

Treatment of niobium pentachloride with cyclohexylphosphine and phenylphosphine in dichloromethane afforded octachlorotetrakis(cyclohexylphosphine)diniobium(IV) (85%) and octachlorotetrakis(phenylphosphine)diniobium(IV) (88%), respectively, as brown-red and dark red crystalline solids. In addition, the phosphonium compound [P(C6H11)H3]2[NbCl6] was isolated in 68% yield from the same preparation of octachlorotetrakis(cyclohexylphosphine)diniobium(IV). Studies are described which demonstrate that the primary phosphine serves as the hydrogen atom source for the formation of the phosphonium salts. Octachlorotetrakis(cyclohexylphosphine)diniobium(IV) can be prepared in 77% yield by addition of cyclohexylphosphine to NbCl4(THF)2 in toluene. The X-ray crystal structure determinations for two dimeric niobium(IV) complexes are described. Octachlorotetrakis(cyclohexylphosphine)diniobium(IV) crystallizes in the triclinic space group P1̄ with a = 9.904(2) Å, b = 10.243(2) Å, c = 10.642(1) Å, α = 76.33(2)°, β = 67.231(8)°, γ = 73.76(2)°, V = 945.7(3) Å3, and Z = 1. Octachlorotetrakis(phenylphosphine)diniobium(IV) crystallizes in the orthorhombic space group Pbca with a = 8.873(2) Å, b = 17.394(6) Å, c = 21.778(3) Å, V = 3361.1(9) Å3, and Z = 4. Octachlorotetrakis(cyclohexylphosphine)diniobium(IV) and octachlorotetrakis(phenylphosphine)diniobium(IV) were evaluated as molecular precursors to niobium(III) phosphide (NbP) films in a chemical vapor deposition reactor. Octachlorotetrakis(phenylphosphine)diniobium(IV) was not volatile and was therefore not a useful precursor. However, octachlorotetrakis(cyclohexylphosphine)diniobium(IV) afforded specular, silver-colored films of NbP with substrate temperatures between 400 and 600 °C. The analysis of the films is presented.