Rhodium(III) sulfate

Rhodium(III) sulfate
Identifiers
CAS Number	(tetrahydrate): 15274-78-9 [PubChem];
3D model (JSmol)	(anhydrous): Interactive image; (monohydrate): Interactive image; (tetrahydrate): Interactive image;
ChemSpider	140097;
ECHA InfoCard	100.030.909
PubChem CID	(anhydrous): 159290; (monohydrate): 91886288; (tetrahydrate): 91886287;
CompTox Dashboard (EPA)	DTXSID20890662 ;
	InChI (anhydrous): InChI=1S/3H2O4S.2Rh/c31-5(2,3)4;;/h3(H2,1,2,3,4);;/q;;;2+3/p-6 Key: YWFDDXXMOPZFFM-UHFFFAOYSA-H; (monohydrate): InChI=1S/3H2O4S.H2O.2Rh/c31-5(2,3)4;;;/h3(H2,1,2,3,4);1H2;;/q;;;;2+3/p-6 Key: MPJHDLITZOASKY-UHFFFAOYSA-H; (tetrahydrate): InChI=1S/3H2O4S.4H2O.2Rh/c31-5(2,3)4;;;;;;/h3(H2,1,2,3,4);41H2;;/q;;;;;;;2+3/p-6 Key: JJITWKYISWZJBI-UHFFFAOYSA-H;
	SMILES (anhydrous): [O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Rh+3].[Rh+3]; (monohydrate): O.[O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Rh+3].[Rh+3]; (tetrahydrate): O.O.O.O.[O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Rh+3].[Rh+3];
Properties
Chemical formula	Rh2(SO4)3
Molar mass	493.98 g·mol−1
Appearance	red solid
Structure
Crystal structure	trigonal
Space group	R3 (No. 148)
Lattice constant	a = 806.8 pm, c = 2204.8 pm
Lattice volume (V)	1242.8×106 pm3
Formula units (Z)	6 units per cell
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H290, H314, H315, H319, H335, H341, H410
Precautionary statements	P203, P234, P260, P264, P264+P265, P271, P273, P280, P301+P330+P331, P302+P352, P302+P361+P354, P304+P340, P305+P351+P338, P305+P354+P338, P316, P317, P318, P319, P321, P332+P317, P337+P317, P362+P364, P363, P390, P391, P403+P233, P405, P501
Threshold limit value (TLV)	0.01 mg/m3 as Rh
	NIOSH (US health exposure limits):
PEL (Permissible)	0.001 mg/m3 as Rh
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Rhodium(III) sulfate is an inorganic compound with the chemical formula Rh₂(SO₄)₃. The anhydrous form is a red crystalline solid. Several hydrates and related compounds have been characterized.

Structure and properties

The anhydrous compound (Rh₂(SO₄)₃) forms red, plate-shaped trigonal crystals.^[1] The dihydrate (Rh₂(SO₄)₃·2H₂O) forms orange orthorhombic crystals.

Compounds with the following formulas have been also studied: [Rh(H₂O)₆]₂(SO₄)₃·4H₂O, (H₃O)[Rh(H₂O)₆](SO₄)₂, [Rh(H₂O)₅OH](SO₄)·0.5H₂O, and [Rh(H₂O)₆]₂(SO₄)(H₂SO₄)_x·5H₂O.^[3] The latter three were characterized by single-crystal X-ray diffraction and found to form monoclinic crystals. All phases are sparingly soluble in ethanol and well soluble in water.

Preparation

Anhydrous rhodium(III) sulfate can be prepared by heating rhodium metal in concentrated sulfuric acid at 400 °C.^[1] It is reported that at a temperature of 475 °C the dihydrate is formed instead.

History

The first attempt to produce rhodium(III) sulfate was in 1929 with the reaction of rhodium(III) hydroxide and sulfuric acid.^[4] Two hydrates were reported, a yellow crystalline pentadecahydrate and a red amorphous tetrahydrate. This was not confirmed due to a lack of structural proof.

References

^ ^a ^b ^c Schwarzer, Stefan; Betke, Annika; Logemann, Christian; Wickleder, Mathias S. (18 January 2017). "Oxidizing Rhodium with Sulfuric Acid: The Sulfates Rh 2 (SO 4 ) 3 and Rh 2 (SO 4 ) 3 ·2H 2 O: Oxidizing Rhodium with Sulfuric Acid: The Sulfates Rh 2 (SO 4 ) 3 and Rh 2 (SO 4 ) 3 ·2H 2 O". European Journal of Inorganic Chemistry. 2017 (3): 752–758. doi:10.1002/ejic.201601247.
^ ^a ^b PubChem. "Sulfuric acid, rhodium(3+) salt (3:2)". pubchem.ncbi.nlm.nih.gov. Retrieved 2026-03-23.
^ Vorob’yova, S. N.; Baidina, I. A.; Alekseev, A. V.; Belyaev, A. V. (2009-12-01). "X-ray study of rhodium(III) sulfates". Journal of Structural Chemistry. 50 (6): 1134–1142. doi:10.1007/s10947-009-0166-0. ISSN 1573-8779.
^ Krauss, F.; Umbach, H. (1929-04-08). "Zur Kenntnis der Doppelsulfate und ihrer Komponenten IV. Über das Rhodiumsulfat und seine Hydrate". Zeitschrift für anorganische und allgemeine Chemie. 180 (1): 42–56. doi:10.1002/zaac.19291800105. ISSN 0863-1786.

[Schwarzer-1] Schwarzer, Stefan; Betke, Annika; Logemann, Christian; Wickleder, Mathias S. (18 January 2017). "Oxidizing Rhodium with Sulfuric Acid: The Sulfates Rh 2 (SO 4 ) 3 and Rh 2 (SO 4 ) 3 ·2H 2 O: Oxidizing Rhodium with Sulfuric Acid: The Sulfates Rh 2 (SO 4 ) 3 and Rh 2 (SO 4 ) 3 ·2H 2 O". European Journal of Inorganic Chemistry. 2017 (3): 752–758. doi:10.1002/ejic.201601247.

[PubChem-2] PubChem. "Sulfuric acid, rhodium(3+) salt (3:2)". pubchem.ncbi.nlm.nih.gov. Retrieved 2026-03-23.

[3] Vorob’yova, S. N.; Baidina, I. A.; Alekseev, A. V.; Belyaev, A. V. (2009-12-01). "X-ray study of rhodium(III) sulfates". Journal of Structural Chemistry. 50 (6): 1134–1142. doi:10.1007/s10947-009-0166-0. ISSN 1573-8779.

[4] Krauss, F.; Umbach, H. (1929-04-08). "Zur Kenntnis der Doppelsulfate und ihrer Komponenten IV. Über das Rhodiumsulfat und seine Hydrate". Zeitschrift für anorganische und allgemeine Chemie. 180 (1): 42–56. doi:10.1002/zaac.19291800105. ISSN 0863-1786.

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