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| Names | |
|---|---|
| Preferred IUPAC name Trimethylindium | |
| Systematic IUPAC name Trimethylindigane[1] | |
| Other names Trimethylindane, indium trimethyl | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.020.183 |
| EC Number |
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| UNII | |
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| Properties | |
| InC 3H 9 | |
| Molar mass | 159.922 g mol−1 |
| Appearance | White, opaque crystals |
| Density | 1.568 g cm−3 (at 20 °C) |
| Melting point | 88 °C (190 °F; 361 K) |
| Boiling point | 134 °C (273 °F; 407 K) (decomposes above 101 °C (214 °F; 374 K)) |
| Reacts | |
| Thermochemistry | |
Std enthalpy of formation(ΔfH⦵298) | 150.5-169.7 kJ mol−1 |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Pyrophoric |
| GHS labelling: | |
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| Danger | |
| H250,H260,H261,H314 | |
| P210,P222,P223,P231+P232,P260,P264,P280,P301+P330+P331,P302+P334,P303+P361+P353,P304+P340,P305+P351+P338,P310,P321,P335+P334,P363,P370+P378,P402+P404,P405,P422,P501 | |
| Related compounds | |
Related compounds | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Trimethylindium, often abbreviated toTMI orTMIn, is the organoindium compound with the formula In(CH3)3. It is a colorless,pyrophoric solid.[2] Unliketrimethylaluminium, but akin totrimethylgallium, TMI is monomeric.[3]
TMI is prepared by the reaction ofindium trichloride withmethyl lithium.[2][4]
Compared totrimethylaluminium andtrimethylgallium, InMe3 is a weakerLewis acid. It forms adducts with secondaryamines andphosphines.[5] A complex with the heterocyclictriazine ligand (PriNCH2)3 forms a complex with 6-coordinate In, where the C-In-C angles are 114°-117° with three long bonds to the tridentate ligand with N-In-N angles of 48.6° and long In-N bonds of 278 pm.[6]
In the gaseous state InMe3 is monomeric, with a trigonal planar structure, and inbenzene solution it is tetrameric.[5] In the solid state there are two polymorphs, a tetragonal phase which is obtained, for example, by sublimation and a lower density rhombohedral phase discovered in 2005,[7] when InMe3 re-crystallised fromhexane solution.
In the tetragonal form InMe3 is tetrameric as in benzene solution and there is bridging between tetramers to give an infinite network. Each indium atom is five coordinate, in a distortedtrigonal planar configuration, the three shortest bonds (ca. 216 pm) are those in the equatorial plane, with longer axial bonds, 308 pm for the In-C bonds joining the InMe3 units to form the tetramers and 356 pm for the In-C linking the tetramers into an infinite network.[8] The solid state structures ofGaMe3 andTlMe3 are similar.[8] The association in the solid state accounts for the high melting point of 89°–89.8 °C compared totriethylindium which melts at −32 °C.[5]
The rhombohedral form of InMe3 consists of cyclic hexamers with 12 membered (InC)6 rings in an extendedchair conformation. The hexamers are interlinked into an infinite network. Indium atoms are five coordinate the equatorial In-C distances average 216.7pm almost identical to the average for the tetragonal form, and the axial bonds are 302.8pm joining the InMe3 units into hexamers and 313.4 pm linking the hexamers to form the infinite network.[7]
Indium is a component of severalcompound semiconductors, including as InP, InAs,InN,InSb,GaInAs,InGaN,AlGaInP, AlInP, and AlInGaNP. These materials are prepared bymetalorganic vapour phase epitaxy (MOVPE) and TMI is the preferred source for theindium component. High purity in TMI (99.9999% pure or greater) is essential for many of these applications. For some materials, electron mobilities are observed as high as 287,000 cm²/Vs at 77 K and 5400 cm²/Vs at 300 K, and background carrier concentration as low as 6×1013 cm−3.[9][10]
Thevapor pressure equation log P (Torr) = 10.98–3204/T (K) describes TMI within a wide range ofMOVPE growth conditions.[11]
TMI ispyrophoric.[12]
