Synthesis and Characterization of Tetrahydrofurfurylcyclopentadienyl Molybdenum Tricarbonyl Dimer:  Evidence for 19-Electron Intramolecular “Solvento” Interactions

Abstract

The synthesis and characterization of a THF pendant, dimeric Mo cyclopentadienyl complex is reported and the structure characterized by NMR, FTIR, and UV-vis spectroscopies. The dimer was found to undergo metal-metal bond homolysis under either photochemical or electrochemical conditions to yield an odd-electron complex. Cyclic voltammetry under varying scan rate conditions from 25 to 10 000 mV/s demonstrates a dynamic equilibrium process that we assign to the formation of either an intramolecular 19-electron (18 + delta) complex or a bare 17-electron complex. Photolysis of the dimer in room temperature solution could be monitored as a loss of the dpi-dsigma transition at 503 nm by transient absorption spectroscopy. The recovery of the transient absorption signal at 410 nm follows first-order kinetics at a rate of 5 x 10(3) s(-1).

Electrochemical analysis of cyclopentadienylmetal carbonyl dimer complexes: Insight into the design of hydrogen-producing electrocatalysts

“…Unfortunately, digital simulation of the response of Mp 2 and Wp 2 was not able to adequately account for the cyclic voltammetry obtained using only the simplified mechanism of Table 1 (Figure SI-27). It is possible that the shapes of the oxidation peak observed in these cases are affected by coupled formation of a 19 electron solvent [34] radical species, [CpM(CO) 3 (NCMe)] [35], upon oxidation of the anion (although the formation of this solvento species in any sizable quantity has also been questioned) [36]. The reasonable fit of simulation without invocation of a solvento species for Fp 2 /Rp 2 suggests that any equilibrium between the 19-electron [37] [CpM(CO) 2 (NCMe)] and the 17-electron [CpM(CO) 2 ] when M ¼ Fe/Ru lies well toward the 17-electron species.…”

Chelate Complexes of Cyclopentadienyl Ligands Bearing Pendant O-Donors

“…a. Molybdenum. W. E. Jones, Jr., and co-workers very recently provided direct experimental evidence for the single species known in this category, namely, [ 1 Mo(CO) 3 ] + , which was formed from [ 1 Mo(CO) 3 ] 2 after electrochemical oxidation . Only indirect evidence (based on transient absorption spectroscopy) has been reported for the existence of the neutral 19-valence-electron chelate 1 Mo(CO) 3 , which appears to be formed in equilibrium with the unchelated 17-valence-electron isomer produced by photolysis of [ 1 Mo(CO) 3 ] 2 .…”

26 Mechanisms of reactions in solution

“…No evidence for either nineteen-electron or charge-transfer intermediates was found. Evidence has been presented 1006 for the formation of seventeen-and nineteen-electron species from [Mo(CO…”