STABLE CATIONIC 17-ELECTRON [LM(CO)3]+ SPECIES (L = 1,4,7-TRIBENZYL-1,4,7-TRIAZACYCLONONANE - M = CR, MO, W) - SYNTHESIS, SPECTROSCOPIC PROPERTIES, AND REACTIVITY - CRYSTAL-STRUCTURE OF [LMO(CO)3](PF6).DMF

The neutral 18-electron complexes LM(CO)3, where L, represents the tridentate capping ligand 1,4,7-tribenzyl-1,4,7-triazacyclononane and M is Cr, Mo, or W, were prepared from M(CO)6and L in dimethylformamide (dmf) at 150 ?C. Oxidation of these diamagnetic complexes in CH2C2with ferrocenium hexafluorophosphate affords the cationic 17-electron species [LM-(CO)3]PF6in good yields. Magnetic susceptibility measurements and ESR spectroscopy confirm the presence of one unpaired electron per cation in these materials. The crystal structure of [LMo(CO)3](PF6)-dmf has been determined by X-ray crystallography (trigonal, space group R3¯ a = 18.299 (4), c = 24.852 (7) Å; Z = 9). The molybdenum atom is in a pseudooctahedral environment comprising three facially coordinated amine nitrogen atoms and three carbonyl ligands. The cation possesses crystallographically imposed C3symmetry. Cyclic voltammetry reveals a reversible one-electron oxidation of LM(CO)3species in dmf at -0.52 V vs Fc+/Fc for the chromium complex, at -0.23 V vs Fc+/Fc for the molybdenum complex, and at -0.305 V vs Fc+/Fc for the tungsten complex. At more anodic potentials a second irreversible oxidation wave has been observed. The reactivity of the LM(CO)3species has been briefly investigated. © 1990, American Chemical Society. All rights reserved.