Bonding in Transition-Metal Methylene Complexes. 3. Comparison of Cr and Ru Carbenes; Prediction of Stable LnM(CXY) Systems

Emily A. Carter, William A. Goddard

Research output: Contribution to journalArticle

62 Scopus citations

Abstract

The electronic structure of the lowest carbene state of a representative early-transition-metal complex, CrCH2+ (6A1 symmetry), has been examined by using ab initio techniques. Its properties reveal a complex with a single σ-donor bond from singlet CH2 to high-spin (d5) Cr+ and no π-back-bond, resulting in a low bond energy (38.7 kcal/mol) and a large carbene–alkylidene state splitting (18.8 kcal/mol). These results are contrasted with Ru carbene (possessing both σ- and π-donor bonds) properties [De(Ru=C) = 65.8 kcal/mol and ΔE(carbene-alkylidene) = 12.9 kcal/mol]. This comparison enables, for the first time, a separation of σ-donor bond strengths from π-donor bond strengths. Finally, using only valence electron properties, we are able to predict stabilities of LnM(CXY) complexes (e.g., how substituents at carbon affect the preference for bridging vs. terminal CXY), discussing trends for the entire transition series.

Original languageEnglish (US)
Pages (from-to)4746-4754
Number of pages9
JournalJournal of the American Chemical Society
Volume108
Issue number16
DOIs
StatePublished - 1986
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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