Tetrarhodium dodecacarbonyl

Tetrarhodium dodecacarbonyl
Names
	IUPAC name tri-μ-carbonyl-1:2κ2C;1:3κ2C;2:3κ2C-nonacarbonyl- 1κ2C,2κ2C,3κ2C,4κ3C-[Td-(13)-Δ4-closo]-tetrarhodium(6 Rh—Rh)
	Other names rhodium(0) carbonyl; rhodium carbonyl; rhodium dodecacarbonyl
Identifiers
CAS Number	19584-30-6 ;
3D model (JSmol)	Interactive image;
ChemSpider	8115932;
ECHA InfoCard	100.039.232
EC Number	243-171-9;
PubChem CID	9940312;
CompTox Dashboard (EPA)	DTXSID90941352 ;
	InChI InChI=1S/12CO.4Rh/c12*1-2;;;; Key: LVGLLYVYRZMJIN-UHFFFAOYSA-N;
	SMILES [Rh-2]1235(C#[O+])(C#[O+])C(=O)[Rh-2]246(C#[O+])(C#[O+])C(=O)[Rh-2]34(C#[O+])(C#[O+])(C1=O)[Rh-3]56(C#[O+])(C#[O+])C#[O+];
Properties
Chemical formula	Rh4(CO)12
Molar mass	747.743 g/mol
Appearance	Red crystals
Solubility	Chlorocarbons, toluene, tetrahydrofuran
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H312, H332
Precautionary statements	P261, P264, P270, P271, P280, P301+P312, P302+P352, P304+P312, P304+P340, P312, P322, P330, P363, P501
Related compounds
Other cations	Tetracobalt dodecacarbonyl, Tetrairidium dodecacarbonyl
Related compounds	Rhodium(III) chloride, Rh6(CO)16, Rh2(CO)4Cl2
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Tetrarhodium dodecacarbonyl is the chemical compound with the formula Rh₄(CO)₁₂. This dark-red crystalline solid is the smallest binary rhodium carbonyl that can be handled as a solid under ambient conditions. It is used as a catalyst in organic synthesis.

Structure, synthesis, reactions

According to X-ray crystallography, Rh₄(CO)₁₂ features a tetrahedral array of four Rh atoms with nine terminal CO ligands and three bridging CO ligands. The structure can be expressed as Rh₄(CO)₉(μ-CO)₃.^[1]

Rh₄(CO)₁₂ is prepared by treatment of an aqueous solution of rhodium trichloride with activated copper metal under an atmosphere of CO.^[2]

4 RhCl₃(H₂O)₃ + 8 Cu + 22 CO → Rh₄(CO)₁₂ + 2 CO₂ + 8 Cu(CO)Cl + 4 HCl + 10 H₂O

Alternatively, the compound can be prepared by treatment of a methanolic solution of RhCl₃(H₂O)₃ with CO to afford H[RhCl₂(CO)₂], followed by carbonylation in the presence of sodium citrate.^[1]

The cluster undergoes thermal substitution with phosphine ligands, L:^[3]

Rh₄(CO)₁₂ + n L → Rh₄(CO)_12-nL_n + n CO

Tetrarhodium dodecacarbonyl quantitatively decomposes in boiling hexane to afford hexadecacarbonylhexarhodium:^[4]

3 Rh₄(CO)₁₂ → 2 Rh₆(CO)₁₆ + 4 CO

Related metal carbonyls

Because of their relevance to hydroformylation catalysis, rhodium carbonyls have been systematically studied to a high degree. The instability of Rh₂(CO)₈ has been a source of curiosity. The analogous binary carbonyl of cobalt, Co₂(CO)₈, is well known. Solutions of Rh₄(CO)₁₂ under high pressures of CO convert to the dirhodium compound:^[5]

Rh₄(CO)₁₂ + 4 CO → Rh₂(CO)₈

Unlike Co₂(CO)₈ which features bridging carbonyls, the main isomer of Rh₂(CO)₈ features only terminal CO ligands. The relative instability of Rh₂(CO)₈ is analogous to the tendency of Ru(CO)₅ to convert to Ru₃(CO)₁₂.

References

^ ^a ^b Serp, P.; Kalck, P.; Feurer, R.; Morancho, R. (1998). Tri-μ-carbonyl-nonacarbonyltetrarhodium. Inorganic Syntheses. Vol. 32. pp. 284–287. doi:10.1002/9780470132630.ch45.
^ S. Martinengo; G. Giordano; P. Chini (1990). Tri-μ-carbonyl-nonacarbonyltetrarhodium. Inorganic Syntheses. Vol. 28. pp. 242–245. doi:10.1002/9780470132593.ch62.
^ Heaton, Brian T.; Longhetti, Luciano; Michael, D.; Mingos, P.; Briant, Clive E.; Minshall, Peter C.; Theobald, Brian R.C.; Garlaschelli, Luigi; Sartorelli, Ugo (1981). "Structural Studies of Rh₄(CO)₁₂ Derivatives in Solution and in the Solid State". Journal of Organometallic Chemistry. 213: 333–350. doi:10.1016/S0022-328X(00)93969-X.
^ Tunik, S. P.; Vlasov, A. V.; Krivykh, V. V. (1977). "Acetonitrile-Substituted Derivatives of Rh ₆ (CO) ₁₆ : Rh ₆ (CO) _16-X (NCMe) _X ( X = 1,2)". Acetonitrile-Substituted Derivatives of Rh₆(CO)₁₆ : Rh₆(CO)_16-x(NCMe)_x (x = 1,2). Inorganic Syntheses. Vol. 31. pp. 239–244. doi:10.1002/9780470132623.ch37. ISBN 978-0-471-15288-0.
^ Brown, D. T.; Eguchi, T.; Heaton, B. T.; Iggo, J. A.; Whyman, R. (1991). "High-pressure spectroscopic studies of reactions of the clusters [Rh₄(CO)_12–x{P(OPh)₃}_x] (x = 1–4) with carbon monoxide or syngas". Journal of the Chemical Society, Dalton Transactions: 677–683. doi:10.1039/DT9910000677.

General reading

King, R. B., "Rhodium: Organometallic Chemistry" Encyclopedia of Inorganic Chemistry 1994, 7, 3494.

[serp-1] Serp, P.; Kalck, P.; Feurer, R.; Morancho, R. (1998). Tri-μ-carbonyl-nonacarbonyltetrarhodium. Inorganic Syntheses. Vol. 32. pp. 284–287. doi:10.1002/9780470132630.ch45.

[martinego-2] S. Martinengo; G. Giordano; P. Chini (1990). Tri-μ-carbonyl-nonacarbonyltetrarhodium. Inorganic Syntheses. Vol. 28. pp. 242–245. doi:10.1002/9780470132593.ch62.

[3] Heaton, Brian T.; Longhetti, Luciano; Michael, D.; Mingos, P.; Briant, Clive E.; Minshall, Peter C.; Theobald, Brian R.C.; Garlaschelli, Luigi; Sartorelli, Ugo (1981). "Structural Studies of Rh₄(CO)₁₂ Derivatives in Solution and in the Solid State". Journal of Organometallic Chemistry. 213: 333–350. doi:10.1016/S0022-328X(00)93969-X.

[Tunik-4] Tunik, S. P.; Vlasov, A. V.; Krivykh, V. V. (1977). "Acetonitrile-Substituted Derivatives of Rh ₆ (CO) ₁₆ : Rh ₆ (CO) _16-X (NCMe) _X ( X = 1,2)". Acetonitrile-Substituted Derivatives of Rh₆(CO)₁₆ : Rh₆(CO)_16-x(NCMe)_x (x = 1,2). Inorganic Syntheses. Vol. 31. pp. 239–244. doi:10.1002/9780470132623.ch37. ISBN 978-0-471-15288-0.

[5] Brown, D. T.; Eguchi, T.; Heaton, B. T.; Iggo, J. A.; Whyman, R. (1991). "High-pressure spectroscopic studies of reactions of the clusters [Rh₄(CO)_12–x{P(OPh)₃}_x] (x = 1–4) with carbon monoxide or syngas". Journal of the Chemical Society, Dalton Transactions: 677–683. doi:10.1039/DT9910000677.

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