Zirconium Clusters from the Reaction of ZrCl4 with HSnBu3 Followed by Addition of Phosphines:  Zr6Cl14H4(PR3)4 Compounds

The reduction of ZrCl4 with HSnBu3 followed by addition of phosphines yields pentanuclear cluster compounds Zr5Cl12(PR3)5H4 (2) and three types of hexanuclear cluster compounds, Zr6Cl14(PR3)4H4 (3), as well as [Zr6Cl18H5]3- (4) and a small amount of [Zr6Cl18H4]4- (5). Separation of these compounds has been achieved by using different solvents in which they have different solubilities and stabilities. The presence of hydrogen atoms and their numbers have been established by 1H NMR spectroscopy. The compounds Zr6Cl14(PR3)4H4 (3a, R = Me; 3b, R = Et; 3c, R = n-Pr) and [HP(t-Bu)2Ph]3[Zr6Cl18H5] (4d) have been characterized by X-ray crystallography. In compounds 3a and 3b, four hydrogen atoms distributed on the eight triangular faces of the Zr6 octahedron were located. Compound 3a·2CH2Cl2 crystallized in the monoclinic space group P21/n with cell dimensions (−75 °C) of a = 11.149(2) Å, b = 11.049(4) Å, c = 20.666(7) Å, β = 103.42(2)°, V = 2476(1) Å3, and Z = 2. Compound 3b·2CH2Cl2 crystallized in orthorhombic space group Pbca with cell dimensions (−60 °C) of a = 12.127(3) Å, b = 21.793(5) Å, c = 23.022(4) Å, V = 6084(2) Å3, and Z = 4. Compound 3c·2.31C6H6 crystallized in triclinic space group P1̄ with cell dimensions (−60 °C) of a = 12.585(1) Å, b = 13.679(2) Å, c = 23.319(4) Å, α = 97.08(2)°, β = 94.77(2)°, γ = 93.30(2)°, V = 3960.6(9) Å3, and Z = 2. Compound 4d·2CH2Cl2·2C6H6 crystallized in monoclinic space group C2/c with cell dimensions (−60 °C) of a = 29.432(4) Å, b = 13.503(1) Å, c = 23.892(3) Å, β = 110.96(1)°, V = 8867(2) Å3, and Z = 4. In compounds 3ac, six zirconium atoms are arranged in a slightly elongated octahedron with four phosphine ligands at the equatorial positions. The distance of Zreq−Zrax (3.359(8) Å) is slightly longer that of Zreq−Zreq (3.308(6) Å), but both of them are shorter than that found in compound 4d (3.416(2) Å).