MOLECULAR-MODELS OF THE SUPERCONDUCTING CHEVREL PHASES - SYNTHESES AND STRUCTURES OF [MO6X8(PET3)6] AND [PPN][MO6X8(PET3)6] (X = S, SE, PPN = (PH3P)2N)

Hexanuclear molybdenum complexes [Mo6X8(PEt3)6] (1, X = S; 2, X = Se) have been prepared by magnesium reduction of the reaction products of Mo3X7Cl4 with triethylphosphine. Treatment of the complexes with sodium amalgam followed by cation exchange with (PPN)Cl (PPN = bis(triphenylphosphine)nitrogen(1+)) gave [PPN] [Mo6X8(PEt3)6] (3, X = S; 4, X = Se). The X-ray structure determinations have revealed that the Mo6 octahedra of the 20-electron complexes 1 and 2 are very regular in contrast to those of the solid-state compounds Mo6X8. The average bond distances are Mo−Mo = 2.663 Å (1), 2.704 Å (2) and Mo−X = 2.445 Å (1), 2.560 Å (2). The one-electron-reduced complexes 3 and 4 are slightly distorted from regular octahedra due to the occupation of the eg orbital. The average bond distances are Mo−Mo = 2.674 Å (3), 2.714 Å (4) and Mo−X = 2.458 Å (3), 2.570 Å (4). The electronic spectra of the neutral complexes indicate absorptions at 991 nm (1) and 1034 nm (2), which are assignable to a HOMO-LUMO transition. The cyclic voltammetry of 1 and 2 in THF solutions shows a quasi-reversible one-electron-oxidation wave and two one-electron-reduction waves. The space group, cell constants, number of observed reflections, R, and Rw are given as follows in that order. 1: {formula-omited}, a = 17.460 (3) Å, c = 19.931 (6) Å, Z = 3, 1423, 0.039, 0.043. 2: {formula-omited}, a = 13.036 (5) Å, b = 20.492 (6) Å, c = 12.208 (2) Å, a = 93.31 (3)°, β = 108.85 (1)°, γ = 88.85 (5)°, Z = 2, 7350, 0.046, 0.041. 3: C2/c, a = 26.212 (9) Å, b = 18.040 (4) Å, c = 21.865 (8) Å, β = 114.87 (2)°, Z = 4, 6708, 0.060, 0.079. 4: C2/c, a = 26.540 (5) Å, b = 18.117 (5) Å, e = 22.032 (4) Å, β = 115.39 (2)°, Z = 4, 5702, 0.067, 0.045. © 1990, American Chemical Society. All rights reserved.