Cyclopentadienyl complexes, spectral

There is a large class of iron organometallic compounds which can be described as molecular, diamagnetic, and highly covalent. They are derived in the main from the parent compounds iron pentacarbonyl, Fe(CO)s, and the cyclopentadienyl complex ferrocene, (jr-CsHslaFe or CpaFe. In view of their large numbers, it is not surprising that considerable Mossbauer spectral data are available, but as we shall now see the interpretation of this data introduces considerable problems. 

The application of mass spectroscopy for the characterization of metal 7r-complexes is becoming increasingly popular. This section deals with the mass spectral data of several 7i-cyclopentadienyl, 7r-arene, and olefin metal 7r-complexes. Extensive studies have been made on Tu-cyclopentadienyl complexes, but little work has been done on the correlation of the mass spectral cracking patterns and energies of 7r-arene and 7r-allyl metal complexes. 

Complexes 41 and 42 were characterized by their IR and H-NMR spectra, and 41 also by elemental analysis. Table III contains the pertinent spectral data. Noteworthy are the very low energy terminal carbonyl bands for 41 and 42 at 1864 cm-1 (hexane). The weak 7r-accepting abilities of PR3 (R = Et, Ph) allow the lone CO ligand to 77-backbond to the Ti(II) center to a much greater degree. The -NMR spectrum of 41 exhibited a doublet (/H-p = 1.5 Hz) at 8 4.75 due to the coupling of the cyclo-pentadienyl protons with the 31P nucleus, while complex 42 exhibited a broad cyclopentadienyl singlet at 8 4.67. 

The UPS of the bent bis(cyclopentadienyl) metal chlorides (CSH5)2MC12 and (CsH4Me)2MCl2, M = Ti, V have also been measured and interpreted with the aid of Fenske-Hall MO calculations (235). In the Ti complexes the 3a, metal-localized MO is vacant, while in the V complexes this orbital is singly occupied, leading to the additional spectral complexities that are expected for the ionization of an open-shell system comparable studies have been made of analogous Zr and Hf compounds (64a). 

A heterodinuclear iridium-ruthenium complex [Ir (Cp )(H20)-(bpm)Ru (bpy)2](S04)2 (Ir -OH2, Cp = j -pentamethyl-cyclopentadienyl, bpm = 2,2 -bipyrimidine, bpy = 2,2 -bipyridine) can also act as an effective catalyst for removal of dissolved O2 by the four-electron reduction of O2 with formic acid in water at an ambient temperature. The Ir complex reacts efficiently with O2, as shown by the spectral titration in Figure 4.24, where the absorption spectra due to Ir are changed to those of Ir -OH2. The titration... 

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