Electronic structure of monodentate-coordinated diphosphine complexes. Photoelectron spectra of Mo(CO)[sub 5](P(CH[sub 3])[sub 2]CH[sub 2]P(CH[sub 3])[sub 2]) and Mo(CO)[sub 5](P(CH[sub 3])[sub 2]CH[sub 2]CH[sub 2]P(CH[sub 3])[sub 2])

Journal Article · Wed Feb 05 00:00:00 EST 1992 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00029a020· OSTI ID:7017372

Lichtenberger, D L; Jatcko, M E ^[1]

---

1. Univ. of Arizona, Tucson (United States)

Photoelectron spectroscopy is used to study the electronic structure of molybdenum carbonyl complexes that contain diphosphine ligands bound to the metal through only one of the two phosphorus atoms. Photoelectron spectra are reported for Mo(CO)[sub 5]DMPE and Mo(CO)[sub 5]DMPM and compared to the spectra of Mo(CO)[sub 5]PMe[sub 3] and the corresponding free phosphine and diphosphine ligands (PMe[sub 3] is trimethylphosphine, DMPE is 1,2-bis(dimethylphosphino)ethane, and DMPM is bis(dimethylphosphino)methane). The energy splittings between the d[sup 6] metal-based ionizations of these complexes indicate that the [pi]-back-bonding ability is the same for each of these phosphine ligands and is relatively small, about 25% that of carbon monoxide. The metal-based ionizations shift only slightly to lower binding energy from the PMe[sub 3] to the DMPE to the DMPM complex due to a slightly increasing negative charge potential at the metal along this series. This would normally be interpreted as slightly increasing [sigma]-donor strength in the order PMe[sub 3] < DMPE < DMPM. However, the difference between the ionization energy of the coordinated lone pair (CLP) of the phosphine and the ionization energy of the lone pair of the free ligand indicates an opposite trend in [sigma]-donor strength with PMe[sub 3] (1.28 eV) > DMPE (1.27 eV) > DMPM (1.23 eV). The shift of the uncoordinated phosphine lone-pair ionization (ULP) of the monocoordinated diphosphine complexes, which is affected primarily by charge potential effects, reveals that the important factor is a transfer of negative charge from the uncoordinated end of the phosphine through the alkyl linkage to the coordinated phosphine. Aside from these subtle details of charge distribution, the primary conclusion is that the diphosphine ligands, DMPE and DMPM, have [sigma]-donor and [pi]-acceptor strengths extremely similar to those of PMe[sub 3].

• DOE Contract Number: FG02-86ER13501
• OSTI ID: 7017372
• Journal Information: Inorganic Chemistry; (United States), Vol. 31:3; ISSN 0020-1669
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
MOLYBDENUM COMPLEXES
ELECTRONIC STRUCTURE
PHOTOELECTRON SPECTROSCOPY
BINDING ENERGY
CARBONYLS
CHARGE TRANSPORT
CHELATING AGENTS
ELECTRONS
IONIZATION
LIGANDS
PHOSPHINES
VALENCE
COMPLEXES
ELECTRON SPECTROSCOPY
ELEMENTARY PARTICLES
ENERGY
FERMIONS
LEPTONS
PHOSPHORUS COMPOUNDS
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
400201* - Chemical &amp; Physicochemical Properties