Synthesis, characterization, and crystal structures of molybdenum complexes of unsymmetrical electron-poor dithiolene ligands

Abstract

Mo(S2C2(CF3)2)3, 1a, has proven a useful p-dopant in organic electronics. To develop more soluble p-dopants, MoS92− was treated with alkynes CF3CCCO2Me and CF3CCCOCF3 to give the dianions of the corresponding tris(dithiolene) complexes, 1b2− and 1c2−, respectively, which were then oxidized to neutral molybdenum tris[1-(methoxycarbonyl)-2-(trifluoromethyl)-ethane-1,2-dithiolene], 1b, and molybdenum tris[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene], 1c, using NO+PF6−. The crystal structures of (NEt4+)21b2−, (NEt4+)21c2−, and neutral 1c have been determined. In all three cases, the metal coordination is approximately trigonal prismatic and the major isomer is cis (approximately C3v). The structure of 1b2− is distorted by a twist towards pseudo-octahedral coordination similar to that seen in structures of 1a2− and Mo(S2C2(CO2Me)2)32−, 1d2−, salts, and that of 1c exhibits marked folds between the planes formed by the ligand atoms and those formed by the Mo and coordinated S atoms, similar to those seen in the structure of 1a. On the other hand, the metal dithiolene core of 1c2− is essentially undistorted from C3v symmetry. The oxidant strength of the neutral molecules increases in the order 1d<1b<1a<1c, with the potentials ranging from −0.02 to +0.39V versus the ferrocenium/ferrocene couple.