Tetramethyl tin

Structural formula
General
Surname	Tetramethyl tin
other names	Tin tetramethyl Tetramethylstannane TTMT
Molecular formula	C 4 H 12 Sn
Brief description	low viscosity, flammable, colorless liquid
External identifiers / databases
CAS number 594-27-4 EC number 209-833-6 ECHA InfoCard 100.008.941 PubChem 11661 Wikidata Q413135
properties
Molar mass	178.848 g mol −1
Physical state	liquid
density	1.29 g cm −3
Melting point	−54 ° C
boiling point	74–75 ° C (without decomposition)
Vapor pressure	146.7 hPa (25 ° C)
solubility	almost insoluble in water (0.06 g · l −1 ), soluble in non-polar solvents
Refractive index	1.441 (at 20 ° C, 589 nm)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 225-300-310-330-410 P: 210-260-264-273-280-284
MAK	0.001 ml m −3 , 0.005 mg m −3
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Tetramethyltin , with the constitutional formula Sn (CH ₃ ) ₄ , is one of the simplest organometallic tin compounds . The clear, colorless, thin, volatile liquid has an unpleasant odor. Tetramethyltin can be used to methylate organic and inorganic halides .

Extraction and presentation

Tetramethyltin can be produced by reacting the Grignard reagent methylmagnesium iodide with tin (IV) chloride (SnCl ₄ ):

${\displaystyle \mathrm {4\ IMgCH_{3}\ +\ SnCl_{4}\ \rightarrow \ Sn(CH_{3})_{4}\ +\ 4\ MgICl} }$

Organometallic compounds of other elements, such as methylaluminum compounds, can also be used for the methylation of SnCl ₄ .

${\displaystyle \mathrm {4\ Al(CH_{3})_{3}\ +\ 3\ SnCl_{4}\ \rightarrow \ 3\ Sn(CH_{3})_{4}\ +\ 4\ AlCl_{3}} }$

SnCl ₄ and methyl chloride can also be reacted with one another directly in the presence of sodium ( Wurtz reaction ):

${\displaystyle \mathrm {4\ ClCH_{3}\ +\ SnCl_{4}\ +\ 8\ Na\ \rightarrow \ Sn(CH_{3})_{4}\ +\ 8\ NaCl} }$

properties

Physical Properties

Tetramethyltin is highly flammable, with a flash point of −12 ° C and a lower explosion limit of 1.9 vol%. It has a density of 1.29 g · cm ⁻³ and a refractive index of 1.4410. It is almost insoluble in water but easily miscible with non-polar organic solvents. In the molecule, the central tin atom - equivalent to the central carbon atom in neopentane - is surrounded by the four methyl groups in a tetrahedral arrangement. The strength of the Sn – C bond is assumed to be 297  kJ / mol .

Chemical properties

Due to the good shielding of the central metal atom and the low polarity of the Sn – C bond, tetramethyltin is stable in air and largely insensitive to hydrolysis . Tetramethyltin reacts with acid chlorides to form methyl ketones and with aryl halides to form aryl methyl ketones :

${\displaystyle \mathrm {Sn(CH_{3})_{4}\ +\ RC(O)Cl\ \rightarrow \ RC(O)CH_{3}\ +\ ClSn(CH_{3})_{3}} }$

Methyl groups can also be transferred from tetramethyltin to inorganic halides such as SnCl ₄ or BBr ₃ :

${\displaystyle \mathrm {3\ Sn(CH_{3})_{4}\ +\ SnCl_{4}\ \rightarrow \ 4\ ClSn(CH_{3})_{3}} }$     ( Kocheshkov rearrangement )

${\displaystyle \mathrm {Sn(CH_{3})_{4}\ +\ 2\ BBr_{3}\ \rightarrow \ 2\ Br_{2}BCH_{3}\ +\ Br_{2}Sn(CH_{3})_{2}} }$

use

• in the MOCVD ( Metalorganic Chemical Vapor Deposition ) process in the production of high-quality tin or tin oxide films for solar cells or gas sensors through thermal decomposition at 400–650 ° C.

${\displaystyle \mathrm {Sn(CH_{3})_{4}\ +\ 8\ O_{2}\quad {\xrightarrow[{-6\ H_{2}O,\ -4\ CO_{2}}]{470\ ^{\circ }C}}\ SnO_{2}} }$

• as a cocatalyst in the polymerization of cycloolefins ( metathesis ). In the first step, the corresponding active tungsten catalysts, methyltrioxorhenium ( MTO ) or other rhenium catalysts are formed by methylation of the central atom:

${\displaystyle \mathrm {WCl_{6}\ +\ 2\ Sn(CH_{3})_{4}\quad {\xrightarrow[{-2\ ClSn(CH_{3})_{3}}]{}}\quad Cl_{4}W(CH_{3})_{2}\ \quad {\xrightarrow[{-CH_{4}}]{}}\quad Cl_{4}W{=}CH_{2}} }$

${\displaystyle \mathrm {Re_{2}O_{7}\ +\ Sn(CH_{3})_{4}\ \rightarrow \ \underbrace {O_{3}ReCH_{3}} _{(MTO)}\ +\ O_{3}ReOSn(CH_{3})_{3}} }$

safety instructions

Tetramethyltin, like many other organic tin compounds, is classified as toxic and must therefore be handled with appropriate care.

• Toxicity to fish, LC ₅₀ : dose 6.44 mg / l (48 h) Oryzias latipes ( red killifish ).
• Toxicity to daphnia and other aquatic invertebrates, EC ₅₀ : Dose: 40 mg / l (24 h) Daphnia magna ( large water flea ).

Organotin compounds damage the central nervous system, which can lead to cramps, narcosis and respiratory paralysis. It is reported that tetramethyltin, which - in addition to triethyl and trimethyltin compounds - is used in the production of solar cells, is rapidly dealkylated to trimethyltin units in mammals. Animal experiments show that trimethyltin acts on the central nervous system and can lead to poisoning, which can manifest itself in reversible nerve damage up to death.

proof

method	Property / signal
NMR	1 H-NMR δ = 0.1 ppm; 13 C-NMR δ = −9.5 ppm; 119 Sn-NMR δ = 0 ppm (common standard)
MS	Tetramethyltin is the first to decompose in the mass spectrum, forming the + Sn (CH 3 ) 3 fragment , which shows a group of signals corresponding to the isotope distribution of tin. The molecular ion + Sn (CH 3 ) 4 is not detected. Other fragments are + Sn (CH 3 ) 2 , + SnCH 3 and Sn +

literature

• Alwyn George Davies, Keith Pannell: Tin chemistry: fundamentals, frontiers, and applications . John Wiley & Sons Ltd, 2008, ISBN 978-0-470-51771-0 ( page 1 in Google Book Search).

Individual evidence

1. ↑ ^{a b c d e f g} Data sheet tetramethyltin for synthesis (PDF) from Merck , accessed on November 13, 2011.
2. ↑ ^{a b c} methyl tin compounds . In: DFG (Ed.): The MAK Collection for Occupational Health and Safety . 2014, p. 13 , doi : 10.1002 / 3527600418.mb744031metd0056 .
3. ↑ ^{a b} Entry on tetramethyltin in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .
4. ↑ Wolfgang Legrum: Fragrances, between stink and fragrance , Vieweg + Teubner Verlag (2011) pp. 68–69, ISBN 978-3-8348-1245-2 .
5. ↑ ^{a b} Scott, WJ; Jones, JH; Moretto, AF: tetramethylstannanes . In: Encyclopedia of Reagents for Organic Synthesis . 2002. doi : 10.1002 / 047084289X.rt070 .
6. ^ ^{A b} Alwyn George Davies: Organotin chemistry, Volume 1 . Wiley-VCH Verlag GmbH & Co. KGaA, 2004, ISBN 3-527-31023-1 ( pages 46-48 in the Google book search).
7. ^ ^{A b} Roland A. Fischer: Precursor chemistry of advanced materials . Springer-Verlag Berlin, 2005, ISBN 978-3-540-01605-2 ( page 7 in the Google book search).
8. ↑ Alwyn George Davies: organotin chemistry, Volume 1 . Wiley-VCH Verlag GmbH & Co. KGaA, 2004, ISBN 3-527-31023-1 ( page 167 in the Google book search).
9. ↑ Yuichiro Okajima et al .: Proceedings of the Third International Symposium on Ceramic Sensors . The Electrochemical Society Inc., 1997, ISBN 1-56677-127-7 ( page 69 in Google book search).
10. ↑ Cynthia J. Bruckner-Lea: Chemical sensors 6 . The Electrochemical Society Inc., 2004, ISBN 1-56677-421-7 ( page 42 in the Google book search).
11. ^ Manfred Dieter Lechner, Klaus Gehrke, Eckhard H. Nordmeier: Macromolecular chemistry: a textbook for chemists, physicists . Birkhäuser Verlag, 2010, ISBN 978-3-7643-8890-4 ( page 100 in the Google book search).
12. ↑ Christoph Janiak, Thomas M. Klapötke , Hans-Jürgen Meyer, Erwin Riedel: Modern inorganic chemistry . de Gruyter, 2003, ISBN 3-11-017838-9 ( page 741 in the Google book search).
13. ↑ Patent WO2010075972A2 : METHOD FOR PRODUCING METHYL trioxorhenium (MTO). ‌
14. ↑ Patent DE3940196A1 : Organo-rhenium oxide cpds. - useful on oxide support materials, as catalysts for metathesis of olefin (s), esp. functional olefin (s). ‌
15. ↑ LD Hamilton, WH Medeiros, PD Moskowitz, K. Rybicka: Toxicology of tetramethyltin and other organometals used in photovoltaic cell manufacture , AIP Conf. Proc., 1988, Volume 166, Issue 1, pp. 54-66; doi : 10.1063 / 1.37131 .
16. ↑ Catherine E. Housecroft, Edwin C. Constable: Chemistry . Pearson Education Limited, 2010, ISBN 978-0-273-71545-0 ( page 367 in Google Book Search).