Tetrairidium dodecacarbonyl

Structural formula
General
Surname	Tetrairidium dodecacarbonyl
other names	Dodecacarbonyl tetrairidium
Molecular formula	[Ir 4 (CO) 12 ]
Brief description	yellow solid
External identifiers / databases
CAS number 18827-81-1 EC number 242-607-5 ECHA InfoCard 100,038,718 PubChem 11967617 ChemSpider 10141599 Wikidata Q4164129
properties
Molar mass	1104.92 g / mol
Physical state	firmly
Melting point	170 ° C (decomposition)
safety instructions
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Tetrairidium dodecacarbonyl is a metal carbonyl with the empirical formula Ir ₄ (CO) ₁₂ . It is a canary yellow compound and a relatively air-stable complex of iridium in the zero oxidation state .

presentation

Tetrairidium dodecacarbonyl can be prepared from iridium (III) chloride in a two-step synthesis. First, hydrated iridium (III) chloride is reductively carbonylated with an anionic dicarbonyl dichlorido complex of the formula [Ir (CO) ₂ Cl ₂ ] ^- as an intermediate. Further reduction with carbon monoxide creates the four-core complex:

${\displaystyle \mathrm {1)\ IrCl_{3}+3\ CO+H_{2}O\rightarrow } }$ ${\displaystyle \mathrm {[Ir(CO)_{2}Cl_{2}]^{-}+CO_{2}+2\ H^{+}+Cl^{-}} }$

${\displaystyle \mathrm {2)\ 4\ [Ir(CO)_{2}Cl_{2}]^{-}+6\ CO+2\ H_{2}O\rightarrow } }$ ${\displaystyle \mathrm {Ir_{4}(CO)_{12}+2\ CO_{2}+4\ H^{+}+8\ Cl^{-}} }$

A simpler synthesis uses sodium hexachloroiridate (IV) as the starting substance, which is first reduced to trivalent hexachloroiridate with sodium iodide . The quantitatively precipitated intermediate compound is filtered off with suction, transferred to methanol and the suspension thus obtained is treated with carbon monoxide under reflux until a red-brown solution has formed. After cooling, potassium carbonate is added to the mixture and the mixture is stirred intensively, the target compound precipitating and suctioning off under protective gas.

${\displaystyle {\ce {Na3IrCl6 + CO -> Ir4(CO)12}}}$

Tetrairidium dodecacarbonyl can be slowly sublimed at 120 ° C in a stream of carbon monoxide and thus purified.

Properties and structure

Each iridium atom is octahedral coordinated by another iridium atom and three carbonyl ligands . Ir ₄ (CO) ₁₂ shows a tetrahedral symmetry ( point group T _d according to Schoenflies ), in agreement with the infrared and Raman spectroscopic data found. It crystallizes in the trigonal space group P 3 (space group no. 143) .

Reactions

The carbonyl ligands of the complex can be replaced relatively easily by other ligands such as phosphine or olefin ligands.

It reacts with alkali hydroxides and cyanides, especially in methanolic and ethanolic suspensions, to form a wide range of polynuclear carbonyl iridates, such as [Ir 6 (CO) ₁₅ ] ^2- or [Ir (CO) ₄ ] ^- .

use

The complex can serve as a catalyst or catalyst precursor for the homogeneous catalytic carbon monoxide hydrogenation and Fischer-Tropsch reactions .

Individual evidence

1. ↑ ^{a b c} Jane E. Macintyre: Dictionary of Inorganic Compounds . CRC Press, 1992, ISBN 0-412-30120-2 , pp. 1397 ( limited preview in Google Book search).
2. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
3. ↑ RD Pergola, L. Garlaschelli, S. Matinengo: Dodecacarbonyltetrairidium: Ir ₄ (CO) ₁₂ . In: Inorganic Syntheses 28: pp. 245-247, doi: 10.1002 / 9780470132593.ch63 .
4. ↑ ^{a b c} L. Malatesta et al .: Dodecacarbonyltetrairidium . In: FA Cotton (Ed.): Inorganic Syntheses . tape 13 . McGraw-Hill Book Company, Inc., 1972, ISBN   07-013208-9  ( defective ) , p. 95-99 (English).
5. ↑ Carl O. Quicksall, Thomas G. Spiro: Metal-metal frequencies and force constants of tetra iridium dodecacarbonyl. In: Inorganic Chemistry. 8, 1969, pp. 2011-2013, doi: 10.1021 / ic50079a042 .
6. ↑ Melvyn Rowen Churchill, John P. Hutchinson: Crystal structure of tetrairidium dodecacarbonyl, Ir ₄ (CO) ₁₂ . An unpleasant case of disorder. In: Inorganic Chemistry. 17, 1978, pp. 3528-3535, doi: 10.1021 / ic50190a040 .
7. ↑ Dario Braga, Fabrizia Grepioni, Giuseppe Guadalupi, Alberto Scrivanti, Renzo Ros, Raymond Roulet: Diolefin derivatives of tetrairidium dodecacarbonyl. Synthesis and crystal structures of Ir ₄ (CO) ₉ L (2,3-η: 5,6-η-norbornadiene) (L = PMe ₂ Ph, PPh ₃ ). In: Organometallics. 6, 1987, pp. 56-62, doi: 10.1021 / om00144a013 .
8. ↑ L. Malatesta and G. Caglio, Chem. Commun., 1967, 420
9. ↑ GC Demitras, EL Muetterties: Metal clusters in catalysis. 10. A new Fischer-Tropsch synthesis. In: Journal of the American Chemical Society. 99, 1977, pp. 2796-2797, doi: 10.1021 / ja00450a065 .