Transition metal oxalate complex

Transition metal oxalate complexes are coordination complexes with oxalate (C2O42−) ligands. Some are useful commercially, but the topic has attracted regular scholarly scrutiny. Oxalate (C2O42-) is a kind of dicarboxylate ligand.[1] As a small, symmetrical dinegative ion, oxalate commonly forms five-membered MO2C2 chelate rings. Mixed ligand complexes are known, e.g., [Co(C2O4)(NH3)4]κ+.[2]

Structures of some metal oxalate complexes
  • [Cr2(ox)5]4-.
    [Cr2(ox)5]4-.
  • Potassium ferrioxalate (.mw-parser-output .template-chem2-su{display:inline-block;font-size:80%;line-height:1;vertical-align:-0.35em}.mw-parser-output .template-chem2-su>span{display:block;text-align:left}.mw-parser-output sub.template-chem2-sub{font-size:80%;vertical-align:-0.35em}.mw-parser-output sup.template-chem2-sup{font-size:80%;vertical-align:0.65em}K3[Fe(C2O4)3]·3H2O)
    Potassium ferrioxalate (K3[Fe(C2O4)3]·3H2O)
  • Oxaliplatin, an anticancer drug
    Oxaliplatin, an anticancer drug
  • [Zr(ox)4]4-
    [Zr(ox)4]4-

Homoleptic complexes

Homoleptic oxalato complexes are common, e.g., those with the formula [M(κ2-C2O4)3]n-: M = V(III), Mn(III),[3] Cr(III), Tc(IV), Fe(III), Ru(III), Co(III), Rh(III), Ir(III). These anions are chiral (D3 symmetry), and some have been resolved into their component enantiomers.[4] Some early metals form tetrakis complexes of the type [M(κ2-C2O4)4]n- M = Nb(V),[5] Zr(IV),[6] Hf(IV),[7] Ta(V),[8]

Bimetallic complexes

Oxalate is often a bridging ligand forming bi- and polynuclear complexes with (κ2,κ'2-C2O4)M2 cores. Illustrative binuclear complexes are [M2(C2O4)5]2- M = Fe(II)[9] and Cr(III)[10]

Photochemistry
Potassium ferrioxalate crystals.

Metal oxalate complexes are photoactive, degrading with loss of carbon dioxide. This reaction is the basis of the technique called actinometry. UV-irradiation of Pt(C2O4)(PPh3)2 gives derivatives of Pt0(PPh3)2.

See also

References
  1. Krishnamurty, Kotra V.; Harris, Gordon M. (1961). "The Chemistry of the Metal Oxalato Complexes". Chemical Reviews. 61 (3): 213–246. doi:10.1021/cr60211a001.
  2. Bernal, Ivan; Cetrullo, James (1990). "The phenomenon of conglomerate crystallization. XIX. Clavic dissymmetry in coordination compounds. XVII". Structural Chemistry. 1 (2–3): 235–243. doi:10.1007/BF00674267. S2CID 96021604.
  3. Lis, T.; Matuszewski, J. (1980). "Structure of potassium tris(oxalato)manganate(III) trihydrate". Acta Crystallographica Section B. 36 (8): 1938–1940. doi:10.1107/S0567740880007558.
  4. Kauffman, George B.; Takahashi, Lloyd T.; Sugisaka, Nobuyuki (1966). Resolution of the Trioxalatocobaltate(III) Ion. Inorganic Syntheses. Vol. 8. pp. 207–211. doi:10.1002/9780470132395.ch55. ISBN 9780470132395.
  5. Cotton, F. A.; Diebold, Michael P.; Roth, W. J. (1987). "Variable Stereochemistry of the Eight-Coordinate Tetrakis(oxalato)niobate(IV), Nb(C2O4)44-". Inorganic Chemistry. 26 (17): 2889–2893. doi:10.1021/ic00264a035.
  6. Fu, Yun-Long; Ren, Jia-Lin; Xu, Zhi-Wei; Ng, Seik Weng (2005). "Bis(4,4′-bipyridinium) Tetrakis(oxalato-κ2O,O′)zirconate(IV)". Acta Crystallographica Section E. 61 (11): m2397–m2399. doi:10.1107/S1600536805033829.
  7. Tranqui, D.; Boyer, P.; Laugier, J.; Vulliet, P. (1977). "Structure cristalline du tétrakisoxalatohafniate de Potassium Pentahydraté [K4Hf(C2O4)4.5H2O]". Acta Crystallographica Section B. 33 (10): 3126–3133. doi:10.1107/S0567740877010395.
  8. Perić, Berislav; Brničević, Nevenka; Jurić, Marijana; Planinić, Pavica; Matković-Čalogović, Dubravka (2009). "[NH4][(CH3)2NH2]2[Ta(C2O4)4]·2H2O: The First (Oxalato)tantalate(V) Complex Structurally Characterized". Structural Chemistry. 20 (5): 933–941. doi:10.1007/s11224-009-9494-0. S2CID 96838371.
  9. Armentano, Donatella; De Munno, Giovanni; Lloret, Francesc; Julve, Miguel (2005). "Bis and Tris(oxalato)ferrate(III) Complexes as Precursors of polynuclear compounds". CrystEngComm. 7 (7): 57. doi:10.1039/b417251e.
  10. Masters, Vanessa M.; Sharrad, Clint A.; Bernhardt, Paul V.; Gahan, Lawrence R.; Moubaraki, Boujemaa; Murray, Keith S. (1998). "Synthesis, Structure and Magnetism of the Oxalato-Bridged Chromium(III) Complex [NBun4]4[Cr2(ox)5]·2CHCl3". Journal of the Chemical Society, Dalton Transactions (3): 413–416. doi:10.1039/a705265k.
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