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).[1] Studies on arsine complexes attracted some major figures in inorganic chemistry: Joseph Chatt, Ronald Nyholm, and Brice Bosnich.[2][3][4]
Ligand properties
[edit]
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
[edit]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.[6] Furthermore, the ligand cone angle is somewhat smaller for arsines vs phosphines: 141° for AsPh3 vs 145° for PPh3.[7]
The inversion barriers (ΔG*)for tertiary arsines have been shown to be near 42 kcal/mol.[8] 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.[3]
The As-C bond is weaker than the P-C bond, which is manifested in some ligand degradations.[9]
Arsines are more reluctant to oxidize to As(V) derivatives. For this reason, alkylarsines are more air-stable than the corresponding alkylphosphines.
Representative ligands
[edit]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.[10][11]
Synthesis and reactions
[edit]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.[6] 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
[edit]- ↑ C. A. McAuliffe, ed. (1973). Transition Metal Complexes of Phosphorus, Arsenic, and Antimony Ligands. J. Wiley. ISBN 0-470-58117-4.
- ↑ 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.
- 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.
- ↑ 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.
- ↑ 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.
- 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.
- ↑ 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.
- ↑ Senkler, G. H.; Mislow, Kurt (1972). "Barrier to pyramidal inversion in ethylmethylphenylarsine". Journal of the American Chemical Society. 94: 291. doi:10.1021/ja00756a059.
- ↑ 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.
- ↑ 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.
- ↑ 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.