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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