He(I) and He(II) Photoelectron Spectra of M[Co(CO)₄]₂ and M[Mn(CO)₅]₂ Complexes (M = Zn, Cd, and Hg)

Abstract

<jats:title>Abstract</jats:title><jats:p> The He(I) and He(II) photoelectron spectra of M[Co(CO)<jats:sub>4</jats:sub>]<jats:sub>2</jats:sub> and M[Mn(CO)<jats:sub>5</jats:sub>]<jats:sub>2</jats:sub> complexes (M = Zn, Cd, Hg) are reported. Bands attributable to metal-metal bonds, metal d-levels and CO orbitals are assigned in agreement with a semi-ionic model, i.e. M<jats:sup>2+</jats:sup> and [M'(CO)<jats:sub>n</jats:sub>]<jats:sup>-</jats:sup>. Relativistic effects prove to be important in assigning these ultraviolet photoelectron spectra.</jats:p>

The He(I) and He(II) photoelectron spectra of some η5-cyclopentadienyl-titanium,-zirconium and -hafnium trihalide complexes

“…The He(I) and He(II) cross section for the Ti, Zr, Hf d orbitals both increase on going down the periodic system (heavy atom effect). In all cases, however, the He(II) cross section is larger than that for He(I) [13,14].…”

“…The third band in the spectra again exhibits a rather poor He(II) intensity, but in He(I) the intensity is about twice that of the second band. This suggests a halogen e-type ionization, probably the e-combination of p-orbitals out of the Cl-Cl-Cl plane and perpendicular to the M-Cl bond, since this corresponds to the normal ordering of Cl-type ionizations in MCl 3 units [13]. The shift of this band on permethylation is rather large (0.94 eV), which indicates a strong mixing with Cp orbitals.…”

Bonding in M(NHBMe)2 and M[Mn(CO)5]2 complexes (M=Zn, Cd, Hg; NHBMe=(HCNMe)2B): divalent group 12 metals with zero oxidation state

“…While Hg[Mn(CO) 5 ] 2 was first synthesized in 1960 by Hieber and Schropp [26], its lighter homologues, M[Mn(CO) 5 ] 2 (M=Zn, Cd), were prepared in 1968 by Burlitch [27]. Later on, some alternative procedures were also reported to synthesize these complexes [28][29][30][31][32]. They were characterized by IR and/or Raman spectroscopic studies which suggest that these complexes possess highly symmetric D 4h or D 4d structures.…”

“…They were characterized by IR and/or Raman spectroscopic studies which suggest that these complexes possess highly symmetric D 4h or D 4d structures. However, an X-ray structure is only available for Hg[Mn(CO) 5 ] 2 showing the molecule with an approximate D 4h symmetry [33,34] Since Mn(CO) 5 − is an 18-electron complex, these complexes are generally described with interaction between M 2+ and two Mn(CO) 5 − ligands, giving the formal oxidation state + 2 for M [30]. But an in-depth bonding analysis for these complexes is missing which leads to the question about the correct oxidation state of the metal center in M(NHB Dipp ) 2…”