The reaction of transition metal atoms with arenes: low temperature π-complex formation

The structure, ordering, and chemistry of molecular overlayers on Rh(111) and Rh(100) single crystal surfaces: A vibrational spectroscopic and LEED crystallographic study

“…In addition to the out-of-plane bending mode, the M-C stretching vibrations should also increase as the interaction with the surface increases. A similar trend was also reported for benzene 1r-complexed to nickel, cobalt, iron, and chromium [183]. the 7r shift.…”

A high-resolution electron energy loss spectroscopy study of the surface structure of benzene adsorbed on the rhodium(111) crystal face

“…The bending vibration for CH groups present in gas-phase molecules is a strong function of the hybridization of the carbon atom, increasing in frequency with increasing hybridization, sp < sp2 < sp3.28 Similar trends are seen in metal-benzene complexes where the CH out-of-plane bending mode (ych) frequency was found to increase in the order: nickel < cobalt < iron < chromium. 27 The CH mode is the most intense in the spectrum and undergoes substantial shifts; hence this bend has been used previously as an indirect means of relating metal-ring bond strengths for both arene-and cyclopentadienyl-metal complexes.39 We CgHg OUT-OF-PLANE CH BEND vs. C6H6 HEAT OF DESORPTION Figure 9. The calculated heats of desorption of molecular benzene and the adsorbed benzene yCh frequency for several metal surfaces.…”

“…This influence was alluded to earlier when we discussed results of infrared studies of metal-arene complexes that showed decreases in the € frequency of 15-45 cm"1 due to higher coordination of the benzene. 27 The origin of this influence is that vibrational frequencies are determined by the shape of the potential well and not only by the depth of the potential well.…”

Late Transition Metals, Metal Halides, Metal Oxides, and Metal Sulfides (Group VIII)

“…The codeposition of benzene, toluene, or mesitylene, with Fe, Co, or Ni yields π-arene complexes that may be 1:1 in stoichiometry, as examined by matrix isolation spectroscopic methods. 63 These are un stable reactive complexes, as first demonstrated by Timms," where an Fe-benzene complex sometimes decomposed explosively at ca -50°C. Addition of H 2 to this unstable complex produced some cyclohexane.…”

“…63 Vinyl halide-metal atom complexes have also been examined spectroscopically, and π-complexation was found, 64 without evidence of oxidative addition having occurred in the temperature range of about 8°-50°K. Using macroscale methods, we do know that oxidative addition does occur, but with CF 2 =CFBr, for example, not until about -100°C or higher.…”