Transition metal arsine complexes

Transition metal arsine complexes are coordination complexes containing one or more arsine ligands. Almost always, the arsine is an organoarsenic compound of the type R3As (R = alkyl, aryl). Studies on arsine complexes attracted some major figures in inorganic chemistry: Joseph Chatt, Ronald Nyholm, and Brice Bosnich.

Ligand properties

Structure of trans-PdCl2(AsPh3)2. (Ph = C6H5)

Arsines are L ligands according to the Covalent bond classification method. In the usual electron counting method, they are two-electron ligands. With respect to HSAB theory, arsines are "soft ligands."

Comparison of arsine and phosphine ligands

An obvious difference between arsine and phosphine ligands is the larger size of arsenic atoms. Consequently, M-As bonds tend to be about 10 picometers longer than M-P bonds. Furthermore, the ligand cone angle is somewhat smaller for arsines vs phosphines: 141° for AsPh3 vs 145° for PPh3.

The inversion barriers (ΔG*)for tertiary arsines have been shown to be near 42 kcal/mol. By contrast, the inversion of a tertiary phosphine occurs with barriers near 30 kcal/mol. Thus, chiral arsines are more configurationally stable than chiral phosphines.

The As-C bond is weaker than the P-C bond, which is manifested in some ligand degradations.

Arsines are more reluctant to oxidize to As(V) derivatives. For this reason, alkylarsines are more air-stable than the corresponding alkylphosphines.

Representative ligands

Symmetrical triorganoarsines are well-established, including triphenylarsine and trimethylarsine. A well studied chelating ditertiary arsine is diars, C6H4(As(CH3)2)2, which gained renown for the stabilization of high oxidation state complexes.

Synthesis and reactions

Metal arsine complexes are heavy analogues of the more widely studied metal-phosphine complexes. Arsine-halide complexes are prepared by reactions of metal halides with preformed arsines. For example, treatment of a suspension of platinum(II) chloride in ethanol with triethylarsine yields monomeric bis(triethylarsine)platinum(II) chloride. Arsine carbonyl complexes are often prepared, like the phosphine analogues, by thermal or UV-induced displacement of CO ligands.

As catalysts for cross-coupling reactions, palladium-arsines are sometimes superior to their phosphine analogues.

References

  1. ↑ C. A. McAuliffe, ed. (1973). Transition Metal Complexes of Phosphorus, Arsenic, and Antimony Ligands. J. Wiley. ISBN 0-470-58117-4.
  2. ↑ Chatt, Joseph; Mann, Frederick G. (1939). "The synthesis of ditertiary arsines. meso- and racemic forms of bis-4-covalent-arsenic compounds". Journal of the Chemical Society (Resumed): 610. doi:10.1039/JR9390000610.
  3. 1 2 Bosnich, B.; Jackson, W. G.; Wild, S. B. (1973). "Metal Complexes of Dissymmetric Arsines. Stereochemistry, Topological Stability, and Spectra of Cobalt(III) Complexes containing a Linear Quadridentate Tetra-tert-arsine Ligand". Journal of the American Chemical Society. 95 (25): 8269–8280. Bibcode:1973JAChS..95.8269B. doi:10.1021/ja00806a012.
  4. ↑ Clark, R. J. H.; Lewis, J.; Nyholm, R. S.; Pauling, P.; Robertson, G. B. (1961). "Eight-Co-Ordinate Diarsine Complexes of Quadrivalent Metal Halides". Nature. 192 (4799): 222–223. doi:10.1038/192222a0.
  5. ↑ Chishiro, Akane; Konishi, Masafumi; Inaba, Ryoto; Yumura, Takashi; Imoto, Hiroaki; Naka, Kensuke (2022). "Tertiary Arsine Ligands for the Stille Coupling Reaction". Dalton Transactions. 51 (1): 95–103. doi:10.1039/D1DT02955J. PMID 34816856.
  6. 1 2 Otto, Stefanus; Muller, Alfred Johannes (2001). "cis-Dichlorobis(triethylarsine)platinum(II) and cis-Dichlorobis(triethylphosphine)platinum(II)". Acta Crystallographica Section C Crystal Structure Communications. 57 (12): 1405–1407. doi:10.1107/S0108270101016043. PMID 11740098.
  7. ↑ Tolman, Chadwick A. (1977). "Steric effects of phosphorus ligands in organometallic chemistry and homogeneous catalysis". Chemical Reviews. 77 (3): 313–348. doi:10.1021/cr60307a002.
  8. ↑ Senkler, G. H.; Mislow, Kurt (1972). "Barrier to pyramidal inversion in ethylmethylphenylarsine". Journal of the American Chemical Society. 94: 291. doi:10.1021/ja00756a059.
  9. ↑ Bosnich, B.; Nyholm, R. S.; Pauling, P. J.; Tobe, M. L. (1968). "A nickel(II)-catalyzed synthesis of a triarsine from a diarsine". Journal of the American Chemical Society. 90 (17): 4741–4742. doi:10.1021/ja01019a049.
  10. ↑ Hazeldean, G. S. F.; Nyholm, R. S.; Parish, R. V. (1966). "Octahedral ditertiary arsine complexes of quadrivalent iron". Journal of the Chemical Society A: 162–165. doi:10.1039/J19660000162.
  11. ↑ Warren, L. F.; Bennett, M. A. (1976). "Comparative study of tertiary phosphine and arsine coordination to the transition metals. Stabilization of high formal oxidation states by o-phenylene-based chelate ligands". Inorganic Chemistry. 15 (12): 3126–3140. doi:10.1021/ic50166a040.