Stannous oxalate
[CAS# 814-94-8]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organotin
• Name: Stannous oxalate
• Synonyms: Tin (II) oxalate
• Molecular Formula: SnC₂O₄
• Molecular Weight: 206.71
• CAS Registry Number: 814-94-8
• EC Number: 212-414-0
• SMILES: C(=O)(C(=O)[O-])[O-].[Sn+2]

Properties

• Melting point: 280 ºC (Decomposes) (Expl.)
• Solubility: water: insoluble, HCl: soluble (Expl.)

Safety Data

• Hazard Symbols: GHS05;GHS07;GHS08 Danger
• Hazard Statements: H302+H312+H332-H302-H312-H314-H317-H318-H332-H334-H372
• Precautionary Statements: P233-P260-P261-P264-P264+P265-P270-P271-P272-P280-P284-P301+P317-P301+P330+P331-P302+P352-P302+P361+P354-P304+P340-P305+P354+P338-P316-P317-P319-P321-P330-P333+P317-P342+P316-P362+P364-P363-P403-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Serious eye damage	Eye Dam.	1	H318
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H312
Skin corrosion	Skin Corr.	1C	H314
Skin sensitization	Skin Sens.	1	H317
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Respiratory sensitization	Resp. Sens.	1	H334
Acute toxicity	Acute Tox.	4	H332
Specific target organ toxicity - repeated exposure	STOT RE	2	H373

Discovory and Applicatios

Stannous oxalate is an inorganic compound consisting of divalent tin (Sn²⁺) and oxalate (C₂O₄²⁻) anions. It is a white to off-white powder that is sparingly soluble in water and is recognized for its reducing properties and sensitivity to oxidation. Its chemical formula is SnC₂O₄, and it belongs to the class of metal oxalates, which have been investigated for various structural, thermal, and catalytic properties. The compound has attracted attention in coordination chemistry and materials science due to the redox activity of tin(II) and the chelating behavior of oxalate ligands.

The history of stannous oxalate dates back to studies on tin(II) salts in the 19th and early 20th centuries, during the systematic characterization of metal-organic complexes. Oxalates were of particular interest because of their strong chelating abilities and ability to form complexes with many metal ions. The preparation of stannous oxalate was typically achieved by mixing aqueous solutions of tin(II) salts, such as tin(II) chloride or tin(II) sulfate, with a soluble oxalate salt, such as sodium or ammonium oxalate. The reaction produces a white precipitate of stannous oxalate, which can be collected by filtration and dried under inert conditions to prevent oxidation of the Sn²⁺ ion to Sn⁴⁺.

The compound is thermally unstable and decomposes upon heating, forming tin oxides and releasing carbon dioxide. This decomposition behavior has been studied in the context of thermal analysis, including thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). These studies help determine the stability range of stannous oxalate and its transformation pathways. The redox nature of the Sn²⁺ center, which is susceptible to oxidation by atmospheric oxygen, necessitates that stannous oxalate be handled under controlled or inert conditions for long-term storage or during analytical measurements.

One of the notable applications of stannous oxalate is in materials chemistry, particularly in the synthesis of tin oxide (SnO₂) nanomaterials. When thermally decomposed in a controlled atmosphere, stannous oxalate can serve as a precursor for SnO₂, a material widely used in gas sensors, transparent conducting films, and as a catalyst support. The morphology and particle size of the resulting tin oxide can be influenced by the thermal treatment conditions and the purity of the precursor. In these applications, stannous oxalate provides a route to obtain fine tin oxide powders without the need for high-temperature calcination of other tin salts.

Stannous oxalate has also been studied for its coordination behavior with additional ligands, allowing it to be used in model systems to study metal-ligand interactions. In such contexts, it provides insight into how tin(II) ions interact with organic ligands in solution and in the solid state. The oxalate group, as a bidentate ligand, forms stable five-membered chelate rings, and this geometry is of interest in the study of coordination compounds and the design of functional metal-organic materials.

In electrochemical research, tin(II) compounds, including stannous oxalate, have been examined as possible electrode materials or electrolyte additives, especially due to their ability to undergo redox transitions. However, the poor solubility and oxidative sensitivity of stannous oxalate limit its direct use in aqueous electrochemical systems, necessitating stabilization strategies or alternative formulations.

Although the compound is not used extensively in commercial applications, it remains of academic interest due to its well-defined structure and redox-active properties. Studies of stannous oxalate contribute to the broader understanding of tin coordination chemistry, the synthesis of metal oxides, and the thermochemistry of metal-organic salts.

References

2015. Photoelectrocatalytic properties of TiO2/ATO composite films. Research on Chemical Intermediates, 41(7).
DOI: 10.1007/s11164-015-2126-y