Phosphinidene complexes M(CO)5-PR: A density functional study on structures and electronic states

Andreas W. Ehlers, Koop Lammertsma, Evert Jan Baerends

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Density functional studies have been carried out for the equilibrium structures of the phosphinidene transition-metal complexes M(CO)5-PR, with M = Cr, Mo, and W and R = H, Ph, OH, and NH2. The free phosphinidenes P-R have triplet ground states, but their M(CO)5 complexes prefer singlet states because of the substantial stabilization of the unoccupied phosphorus pπ acceptor orbital. This follows from calculations based on the local density approximation, including nonlocal corrections for correlation and exchange self-consistently. The M(CO)5-PR bond is investigated using a bond energy analysis in terms of electrostatic interaction, Pauli repulsion, and orbital interaction. A symmetry decomposition scheme affords a quantitative estimate of the σ and π bond strengths, which gives an interpretation of the donor-acceptor complexes within the Dewar-Chatt-Duncanson model. It is shown that the investigated ligands are strong π-acceptors and even stronger σ-donors. In the case of unsubstituted PH complexes, the ground state is a singlet due to strong preferential stabilization by π-back-donation into the empty phosphorus pπ orbital. When substituents are present, the singlet state is already relatively stabilized in the free phosphinidene due to π-donation from the substituent. The π-back-donation from the metal fragment decreases accordingly due to competition with this substituent π-donation but remains effective in further preferentially stabilizating the singlet.

Original languageEnglish
Pages (from-to)2738-2742
Number of pages5
Issue number13
Publication statusPublished - 22 Jun 1998
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry


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