Synthesis and chemical characterization of the hexanuclear anions [Ir6(CO)14X]–(X = Cl, Br, I, or SCN). Crystal and molecular structures of [PPh4][Ir6(µ-CO)2(CO)12(µ-Br)] and [N(PPh3)2][Ir6(µ-CO)12(µ-X)](X = I or SCN)

Abstract

The salts of the monosubstituted hexanuclear anions [Ir₆(CO)₁₄X]^–[X = Cl (1), Br (2), I (3), or SCN (4)] have been prepared by treating [Ir₆(CO)₁₆] with halides or pseudohalides at room temperature in tetrahydrofuran solution. Complex (2) crystallizes in the monoclinic space group P2₁/c(no. 14) with a= 12.653(4), b= 25.566(10), c= 13.351(2)Å, β= 91.04(2)°, and Z= 4, (3) crystallizes in the monoclinic space group P2₁/c(no. 14) with a= 17.444(3), b= 14.791(3), c= 23.332(5)Å, β= 113.32(2)°, and Z= 4, and (4) crystallizes in the monoclinic space group P2₁(no. 4) with a= 9.441(3), b= 36.952(9), c= 15.663(4)Å, β= 91.44(2)°, and Z= 4. The three structures have been solved by conventional Patterson and Fourier methods and refined by full-matrix least-squares to final conventional R values of 0.029 (2), 0.036 (3) and 0.045 (4) on the basis of 4 223, 5 427, and 7 181 independent counter data having I > 3σ(I). The three anions consist of slightly distorted octahedra of iridium atoms bearing twelve terminal and two edge-bridging carbon monoxide groups. In all cases the halogen atoms or the pseudohalogen group adopt a bridging co-ordination on an Ir–Ir edge.