Research Project: Organotin Compounds Student name: Harry Chan Student number: 971966620 Instructor: Professor M. Denk Due date: April 12, 2000 The History of Organotin Compounds E. Frankland discovered the first orgaontin compound in 1849. The first organotin compound was diethyltin diiodide (Et2SnI2). From then on the research on organotin chemistry has been conducted under this very day. The development of organotin chemistry was very slowed in the first 50 years of its development, mainly because the lack of effective and reliable methods to produce compounds1. 4 years after the discovery of Et2SnI2, Frankland introduced diethyltin oxide, dichloride and an air-sensitive diethyltin that when heated above 150oC deposited tin and produced tetraethyltin2. From 1850-1880, chemists such as Cahours, Riche, C.Lowig, A.Strecker, had all contributed to the development of organotin compounds. Around 1900, the development of organotin compounds had started to be in rapid grown. The reason for such was the availability of organomagnesium halides as alkylating and arylating agents3. The Grignard reagents was important in the development of organotin compounds since its high electropositivity of Mg allows the transfer of hydrocarbon radicals to most main group metal. Large-scale application of organotin compounds occurred in the 1930’s. The work by Yngve and Carbide and Carbon Chemical Corp. discovered one of the major use of organotin compounds till this very day: the heat-stabilizing effect on PVC4. Such discovery increased the pace of development of organotin compounds and attracted more Sawyer, A. K., Organotin Compounds, volume 1, p.1. Marcel Dekker, Inc., (1971) Neumann, W. P., The organic chemistry of tin, p.1. John Wiley & Sons Ltd., (1970) 3 Sawyer, A. K., Organotin Compounds, volume 1, p.1. Marcel Dekker, Inc., (1971) 4 Ibid, p. 2. 1 2 input in such research area. The demand of organotin compounds also increased from 50 tons in 1950, to 2000 tons in the 60’s, to 25,000 tons in 19755. The analysis of Sn-H bond started in 1955 by Noltes provided more mechanistic options such as additional reaction (or called hydrostannations) and catalytic decomposition of Sn-H to produce Sn-Sn6. R3SnH + CH2 CH - R' R3Sn - CH2CH2R' From the 1950’s to present day, the researches on organotin compounds had been one of the mostly researched areas in organometallic chemistry. For example, the highly reactivity of Sn-H bond, the production of C-Sn bond, organotin halides, Sn-N, Sn-O, SnP, Sn-S, SnSe, Sn-Te, and their physical properties such as IR spectroscopy, the 1H, 13C NMR spectroscopy, the 119Sn Mossbauer spectroscopy. The application of organotin compounds in the 60’s was mainly the stabilizer of polyvinyl chloride (PVC). It was also involved in agriculture and biology. Nowadays organotin compounds are also involved in biocidal activitiy and as anticancer reagent. The new uses of organotin compounds will be discussed in the paper, also with their toxicity and environmental impact. 5 Zuckerman, J. J., Organotin Compounds: New Chemistry and Applications, p.2. American Chemical Society, (1976) 6 Sawyer, A. K., Organotin Compounds, volume 1, p.3. Marcel Dekker, Inc., (1971) Structure of organotin compounds Tetravalent compounds Table 1. Bond distances (pm) for tetravalent organotin compounds Compound Me4Sn Me3SnH Me2SnH2 MeSnH3 SnH4 Me3SnCCH Me3SnccSnMe3 (CH2=CH)4sn (HCC)4Sn (HCC)3SnI (F3CCC)4Sn Ph4Sn Me3SnCl Me2SnCl2 MeSnCl3 SnCl4 E-C E-H or E-X 214.4 214.9 171 215.3 168 214.3 170 214.1(Me) and 212.6 171.1 212.7(Me) and 209.5 211.6 206.7 206 206 264.5 207 216.8 210.6 235.1 210.9 232.7 210.4 230.4 228.1 The bond length of tetravalent compounds is shown above. Molloy, Zuckerman and Haaland obtained these data in gas-phrase7. The general trend in the bond length of simple tetravalent compounds is that the E-C bond length decreases, as the R-group that attaches to them becomes bigger. However, the decreased in bond length remains within 1 ppm. Alkyls group with organotin compounds had shown some interesting study. For example through the 158K X-ray study for Me4Sn suggested the molecule has a 3-fold axis with 3 different Sn-C bond length: 213.8pm, 210.2pm, 214.4pm. The crystal 7 Patai, S., The chemistry of organic germanium, tin and lead compounds, p. 99. John Wiley & Sons Ltd., (1995) structures of another alkynyl-tin compound Sn(C≡CR) 4 showed deviation from the theoretical CSnC angle that would be between 207.4 – 207.9 pm8. For aryls compounds, for example Ph4Sn in table 1, there was a sign of steric effect based on the measured Sn-C length. The following table for Sn-C bond of arylorganotin compounds showed the effect of steric. Table 2. Average E-C bond lengths for Ar4E compounds by crystallographically9 E/Ar Ph o-Tol m-tol p-tol C6F5 Sn 214.3 215.2 215 214.7 212.6 Other aryl compounds such as Sn (p-C6H4Oet) 4 showed that the presence of the Oet group twisted out of the plane and releases some of the steric strain. The center Sn therefore had lost is symmetry but the structure is very close to tetrahedral. Analyzing the triphenylvinyltin showed the presence of intramolecular steric pressures compound. The Sn-C bonds are equal but with an average twist angle of 51.6o, which are 7o less than SnPh410. Rings containing 4-coordinate isolated Sn The ring structure of 4-coordinate Sn compounds is divided into 4-ring, 6-ring, 7-ring, 8ring or even more complex. The bond length of a 6-ring compound SnBu2t had been reported as followed: Table 3: bond length for SnBu2t SnR2 SnBu2t Sn-C (pm) 219.4 Sn-O (pm) 196.5 CEC (degree) 119.5 OEO (degree) 106.9 8 Patai, S., The chemistry of organic germanium, tin and lead compounds, p. 99. John Wiley & Sons Ltd., (1995) 9 Ibid, p. 104. 10 Ibid, p. 105. EOE (degree) 133.1 The four-ring structure is symmetrical in most cases. The [R2EY]2 ring is very common for heavy Y group and bulky R. The structures of R2SnS, R2SnSe and R2SnTe were determined as followed: R Y Sn a R Sn b Y R Y= A= B= Aa = Bb = Aa’ = a' R S 243 221 86o 117o 94o Se 255 218 83o 115o 98o Te 276 220 80o 117o 100o 4-ring structures had also been determined: Cl Me Sn Sn Me Me2 Cl Me N N Cl Sn Me2 A = 215.6 – 217.9 pm B = 208.8 – 212.2 pm C = 212 pm D = 255.7 – 261.5 pm Dd = 162.4o – 165o E = 313 pm Sn Cl Me Some more complex ring compounds have also been analyzed. For example, the 5membered ring SnOSnC=C, which obtained from the oxidation of Sn-Sn bond of the SnSnCC ring11. H O R2Sn SnR2 Organotin compounds with coordination numbers above 4 The acceptor power decreases when the number of organic group that attached to tin increases. The general geometry for coordination number 5 is trigonal bipyramidal structure. The bond in the axial position in this case is mostly longer than the equatorial bonds. The structure of tetraorgano compounds, triorgano compounds, diorgano compounds, mono-organo compounds and polynuclear compounds have been analyzed. The following structures are just some of them. Me2HCC Et C BEt2 Me Sn C Me C CHMe2 tetraorgano compounds 11 Ibid, p.114. R2 Sn R OH O R Sn Sn RSn RSn Sn O R Sn R Sn R RSn SnR2 R2Sn Sn Sn Sn O O R R RSn R B Ar SnR RSn RSn Sn R cluster structure for polynuclear organotin compounds Diorgano compounds There are also some important structure determined in the 1980’s and 90’s. For example the structure determination of organotin fluorides by Jagirdar et. al. Some of the examples are the X-ray study of Me2Sn (F)CH2CH2P(O)Ph2 and (2-Carbomethoxy-1,4cyclohexadien-1-yl)dimethyltin fluoride. H3C F F O Sn O P H3C Me2Sn(F)CH2CH2P(O)Ph2 Sn O CH3 CH3 Me2Sn(F)[2-C(O)OMe- 1,4 -Chd] The X-ray structure of Me2Sn(F)CH2CH2P(O)Ph2 suggested that the pentacoordination around tin resulted a distorted trigonal bipyramidal geometry. The Me2Sn(F)[2- C(O)OMe-1,4-cyclohexadienyl is the first hexacoordinated triorganotin compound that has a Sn-O bond. There is the distortion of the trigonal bipyramidal due toe the nucleophilic attack of the C=O to fluorine, resulting the extended feature of tetrahedron around the tin. Beside there is an intermolecular nucleophilic attack of the F atoms to the cyclohexadienyl group, resulted the distortion of octahedra arrangement of the bonding12. Another important structure was the diorganotin difluorides, R2SnF2. The vibrational and 119 Sn Mossbauer spectra suggested that the Sn in the hexacoordinated arrangement has a linear C-Sn-C group13. Diorganotin difluorides has the tendency to from polymeric structures due to the intermolecular attraction. The coordination number for increases from 4 to 6 due to Lewis acidity. The compound Me2SnF2 form a sheets of Sn and F atoms, and every tin atom is bridged to the 4 neighbors by the existence of disposed F atom14. H3C CH3 Sn Sn F H3C CH3 F F Sn CH3 Sn F H3C CH3 CH3 Sn H3C CH3 molecular structure of Me2SnF2 12 Jagidar, Murphy and Roesky, Progress in inorganic chemistry, 48, 414-415 (1999) Ibid, p. 418 14 Ibid, p. 419 13 Physical and Spectroscopic Properties IR spectroscopy Infrared spectroscopy has been widely use in the structure determination of orgaontin compounds. Group frequencies are easy to identify for organotin compounds. The reason being that tin atom has a large mass, and the internal vibrations of organic groups that are attached to the tin atom are distinct from each other. The atoms that are connected directly to the tin atom provide the frequencies of skeletal vibrations for structural analysis. The Sn-C stretching provides important information about the structure, and it depends on the organic group that is attached to the Sn. The Sn-C stretching also influence by the coordination number of the Sn atom15. Sn-H stretching vibration also provided information about the structure of organotin compounds. The Sn-H stretching vibration will be higher if there is the presence of electronegative group attached to the Sn atom, with H attached to Sn atom. Sn-O vibration had a range of 300-800 cm-116. The following are the tables for some of the IR stretching measurement for different organo tin compounds: Compound 4 Sn-C bond Me4Sn Et4Sn Pr4Sn Bu4Sn Me3SnCCH State Liquid Liquid Liquid sol in CS2 Liquid 3 Sn-C bond Me3SnCl sol in cyclohex. Me3SnBr sol in cyclohex. Me3SnI sol in cyclohex. 15 16 v(Sn-C) (cm-1) Compound 2 Sn-C bond 528 Me2SnCl2 508s Me2SnI2 590s,500s Et2SnCl2 592s, 503s Et2SnI2 538vs, 517w Bu2SnCl2 Bu2SnI2 542s, 513w 539s, 511m 536m, 508w State v(Sn-C) (cm-1) sol in CS2 sol in cyclohex. sol in CS2 sol in benzene sol in CS2 sol in benzene 560, 524 542m, 511w 531, 497 520m, 490m 602, 517 592m, 508m 1Sn-C bond MeSnCl3 soln MeSnI3 sol in cyclohex. 551-546w-m 527w Sawyer, A. K., Organotin Compounds, volume 3, p.999. Marcel Dekker, Inc., (1971) Ibid, p. 1001. Me3SnOH Et3SnI Et3SnOH Bu3SnCl Bu3SnBr Bu3SnI solid sol in cyclohex. solid liquid sol in cyclohex. sol in cyclohex. 540s 506m, 482w 510vs, 485m 601s, 513m 599s, 503m 598s, 501s EtSnCl3 BuSnCl3 sol in benzene liquid 522w 596, 518 NMR spectroscopy There are in total 10 stable isotopes for tin and 3 of them have non-zero magnetic moments and a nuclear spin I = ½. They are 115 115 Sn, 117 Sn and 119 Sn. The abundance of Sn is too low for any practical use. The 117Sn and 119Sn provide complex NMR spectra since both of the isotopes are couple with –CH and –CH. The chemical shift s in the 117 Sn and 119 Sn spectra can be as much as 1800ppm. The direct spin-spin coupling constants have the magnitude of 2000cps whereas the indirect spin-spin coupling constants only have a magnitude of 50-100cps. The following are the tables of NMR measurement for different organotin compounds. Formula organotin and organotin halides Me3SnMe Me3SnEt Me3SnPr Me3SnBu Me3SntBu Me3SnCH2Ph Me3SnPh T 9.93-9.96 9.97-9.95 9.96-9.93 9.97-9.92 9.99-9.97 9.98 9.73 Me4Sn Me3SnEt Me3SnBu MeSnEt3 Et4Sn PhSnMe3 PhSnEt3 Ph3SnEt Me3SnCl (M3CH2)SnCl (ClCH2)3SnCl J117/119(Sn-Me) J117/119(Sn-Et) 51.5-52.0/54.3-54.4 49.9-50.2/52.2-52.6 50.0-50.2/52.3-52.5 49.9-47.9/49.7 47.5-47.9/49.7-50.2 50.8/52.9 52.2/54.6 52.0/54.3 50.5/52.8 50.4/52.6 47.1/49.3 74.4/77.9 68.6/72.0 65.7/69.2 52.9/55.2 70.5/74.0 79.7/83.2 9.34-9.37 8.64 6.31 56.0/58.5 38.7 18.3 Me3SnBr (M3CH2)SnBr Me2SnCl2 9.2 8.61 8.84 organotin hydrides T Me3SnH Et3SnH Pr3SnH Bu3SnH Ph3SnH Me2SnH2 Et2SnH2 Pr2SnH2 Bu2SnH2 Ph2SnH2 MeSnH3 5.27 5.00-5.24 5.21 5.22 3.03,3.16 5.55 5.25 5.42 5.43 3.98 5.86 56 37.5 66.6/69.7 J117/119(Sn-H) 1664/1744 1539/1611 1533/1605 1532/1609 1850/1935 1717/1797 1616/1691 1615/1685 1619/1690 1842/1927 1770/1852 Synthesis of organotin compounds Sn-C bond The reaction between tin and organic halide is the most general method to produce a Sn-C bond: 2R-X + Sn R2SnX2 Alkyl halides are also used to synthesis the Sn-C bond. The reactivities of alkyl halides decreases in the order of: RI> RBr> RCl and MeX> EtX> PrX17. Example of the use of OH2 (PhCH2)3SnCl PhCH2Cl + Sn toluene (PhCH2)2SnCl2 alkyl halides is as follow: No information on the price or hazard of this reaction. Diorganotin halides can be obtained by reacting tin, HCl, and a , -unsaturated dihalide (1). Alkyltin trihalide can be obtained by reacting tin halides with alkyl halides (2). Sn + 2HCl + 2 H2CCHY Cl2Sn(CH2CH2 Y)2 (1) Y = CO2R, COR, CONR2, or CN RBr 17 + SnBr2 Et3Sb RSnBr3 (2) King, R. B., Encyclopedia of Inorganic Chemistry, volume 8, p. 4173. John Wiley & Sons Ltd., (1994) The price for Sn powder is about $70.70 per 250g. For HCl, each 100mL costs about $48.90. However the price for H2CCHCN and the rest are unknown, the cost of the reaction cannot be calculated. The synthesis of Sn-C can also be obtained from Sn(IV) halides. The use of more electropositive metals is important in such reaction (3). R4-nSnXn + nR'-M R4-nSnR'n (3) No information on the price or hazard of this reaction The addition of organotin hydrides to alkenes and alkynes can also synthesize the Sn-C R3SnH + R3Sn (4) R3SnH + R3Sn bond (4). No information on the price or hazard of this reaction H Distannanes R3SnX 2 R 3SnH Mo -H2 cat. (5) R3Sn SnR3 R3SnX + R3SnM R 3SnH + R3SnNR'2 The general method to produce distannanes is as followed: Linear Polystannanes The synthesis of tristannanes and tetrastannanes can be achieved by the hydrostannolysis reaction of diorganotin dihydrides and 1,1,2,2-tetraorganodistannes18 (6). 2 R'3Sn-NMe2 + H-(R2Sn)n-H R'3Sn-(R2Sn)n-SnR'3 (6) No information on the price or hazard of this reaction The reaction of triorganotin anions with diorganotin dihalide can also synthesize linear polystannanes (7). On the similar basis, tetraorganotin can also be produce by reacting diorganotin dihalide with 1,2-diiodo-1, 1, 2, 2-tetra (t-butyl) distannane (8). 2Ph3SnLi + I-(But2Sn)-I 18 Ph3Sn-(SnBut2)-SnPh3 (7) Sita, L. R., Advances in organometallic chemistry, 38, 205 (1995) 2 Ph3SnLi + I-(But2Sn)2-I Ph3Sn-(SnBut2)2-SnPh3 (8) Branched Polystannanes The reaction of Ph3SnLi and SnCl4 produced (Ph3Sn)3, which is the first synthesis of branched polystannanes19(9). The synthesis of branched polystannanes can also be achieved by hydrostannolysis reaction of organotintrihydrides and (dimethylamino) trimethylstannane (10). Ph3SnLi + SnCl4 (Ph3Sn)3Sn RSnH3 + 3 Me2N-SnMe3 (9) (Me3Sn)3SnR (10) R= Me, Et, Bu, But, Ph SnCl4 is a toxic compound. It is toxic by inhalation, upon contact with skin or swallowed. The compound is either in a white or yellow form. The LD50 for the compound is 120mg/kg by IPR-RAT. Cyclopolystannanes Sakurai and co-workers have achieved the synthesis of monomeric divalent diorganotin compounds just recently. The compound had been shown that it is monomeric in solution and in solid states20. TMS TMS Sn 19 20 Ibid, p. 215 Ibid, p. 217 TMS TMS The following are other methods of synthesizing cyclopolystannanes compounds. TMS TMS Li . SnCl4 Li Sn TMS R2SnCl2 + TMS ButMgBr R2Sn SnR2 R2Sn RLi + SnCl2 Et2O n SnR2 R2 Sn X -78oc R Sn 2 Sn R Sn R2 No information on the price or hazard of these reactions SnCl2 * 2 H20 + 2 (CH3CO)2O SnCl2 + 4 CH3CO2H (11) Synthesis of SnCl2 226g of tin(II) chloride dihydrate was added to 204g of acetic anhyride21. No information on the price or hazard of these reactions 21 Herrmann, W. A., Synthetic methods of Organometallic and Inorganic Chemistry, volume 2, p. 271. Geory Thieme Verlag, (1996) Application of organotin compounds PVC stabilizers During the synthesis of PVC, the temperature will reach up to 180-200oC. At this temperature PVC started to decompose. The decomposition is evident by the discoloration of the compound, from yellow to brown and at the end to black 22. The use of a stabilizer is require in order to prevent such decomposition of occurring and organotin compounds are good stabilizers in this case. Diorganotin and triorganotin thiolates and carboxylates are the mostly used organotin as stabilizers. The decomposition occurs when there is a loss of HCl. The loss of HCl resulted in decomposition and discoloration. The addition of organotin compounds will inhibit the evolution of HCl gas. The addition of Sn-C bond to PVC has anionic exchange with the chloride in the polymer and therefore provides a stable mixture. Catalytic Applications Dialkyltin dicarboxylates are used as catalysts for polyurethane foam formation. Monobutyltins have been used as catalysts for transesterification and esterifications. Biocidal Applications Fungal control –One of the major uses of organotin compounds is as the antifungal agents. The first compound that was used as antifungal agent was triphenyltin acetate. In trialkyl tin compounds, tirmethyltin compounds are the most toxic to mammals and insects. Triethyltin compounds are most toxic to mammals; tripropyltins is 22 Sawyer, A. K., Organotin Compounds, volume 3, p.933. Marcel Dekker, Inc., (1971) most toxic to Gram-negative bacteria; and tributyltin compounds are most toxic to Gramnegative bacteria and fungi23. The diseases that such compounds attacked are late blight in potatoes, leaf spot in sugar beets and leaf spot in celeriac24. Intestinal worms removal for chickens – dibutyltin dilaurate had been used as anthelmintic. For example a drug named Wormal which contains piperazine, phenothiazine, and dibutyltin dilaurate was used for such purpose. Industrial uses Wood preservation – since organotin compounds are antifungal agents, they were also being used in wood preservation process. Both triethyl and tributyltin compounds are used. A higher concentration of organotin compounds can even prevent the attack by insects25. Slime control in paper mills – papermaking involves the use of large quantity of water. The nutrients content for the water favors the growth of microorganisms. In this case slime is formed. Tributyltin oxide was added to slime in order to eliminate such compounds26. Protection of Cables from rodent attack – experiments had shown that organotin compounds, tributyltin chloride in this case, can be an effective rodent repellent in the 70’s. The R50 of triphenyltin chloride for mice was 6.9 mg/cm2 27. 23 King R. B., Encyclopedia of Inorganic Chemistry, volume 8, p.4194. John Wiley & Sons Ltd., (1994) Sawyer, A. K., Organotin Compounds, volume 3, p.953. Marcel Dekker, Inc., (1971) 25 Ibid, p. 955. 26 Ibid, p. 957 24 Latest Uses of organotin compounds One of the latest use of organotin compounds was the use of labelled tin compounds in reactions. There are 2 types of tin compounds that are isotopically labelled and synthesized. The first type was prepared by using specific isotopes of tin. The isotope in a group bonded to the tin atom prepared the second type. The details of these reactions will not be discussed in this research. The major use of these labelled tin compounds was to labelled substrate during reduction reactions. Computational Methods28 The computation chemistry for heavy main group elements had been made possible by the ab initio program. Such program allows one to deal with the large number of electrons of heavier element such as tin. The improvement of pseudo-potential methods also improves the calculation of heavy elements become less time consuming. The structure analysis of organotin compounds relies heavily on the use of X-ray spectroscopy. For example, the structure determination in the journal by Jagirdar et. al. are conducted by the use of X-ray diffraction and X-ray crystallography. Beside the use of solid state 119Sn NMR also involved in such analysis. 27 Ibid, p. 960 Patai, S., The chemistry of organic germanium, tin and lead compounds, p. 587-593. John Wiley & Sons Ltd., (1995) 28 Library Resources The most useful book in the research project is The chemistry of organic germanium, tin and lead compounds. This book provided the most useful information about the topic, at the same time this book is the latest among all books. The Organotin Compounds series by Sawyer provided most of the background information about the topic, but the series was out of dated. Most of the resources that were used in this project were from the Chemistry Library. The books that were recommended are not sufficient to provide all the information for this project. The monthly journal Advances in organometallic chemistry and Progress in inorganic chemistry are essential because they had provided the latest direction and discovery for the topic. References 1. Dickerson, A.F., Comprehensive Inorganic Chemistry, volume 2, 1st edition. Trotman: (1993), Great Britain. 2. Baines, K.M. and Stibbs, W.G., Advance in organometallic chemistry, 37, 304 (1996) 3. Herrmann, W. A., Synthetic Methods of Organometallic and Inorganic Chemistry, volume 2, Geory Thieme Verlag: (1996), Germany. 4. Jagirdar, Murphy and Roesky, Progress in inorganic chemistry, 48, 404, John Wiley & Sons: (1999), United States. 5. King, R. B., Encyclopedia of Inorganic Chemistry, volume 8, p. 4172-4195, John Wiley & Sons Ltd. : (1994), Great Britain. 6. Neumann, W. P., The organic chemistry of tin, John Wiley & Sons Ltd., (1970), England. 7. Patai, S., The chemistry of organic germanium, tin and lead compounds, John Wiley & Sons Ltd., (1995), Great Britain. 8. Poller, R.C., The chemistry of organotin compounds, Logos Press Limited, (1970), Great Britain. 9. Sawyer, A. K., Organotin Compounds, volume 1, Marcel Dekker, inc., (1971), New York. 10. Sawyer, A. K., Organotin Compounds, volume 2, Marcel Dekker, inc., (1971), New York. 11. Sawyer, A. K., Organotin Compounds, volume 3, Marcel Dekker, inc., (1971), New York. 12. Sekiguchi, A. and Sakurai, H., Advances in organometallic chemistry, 37, 18, Academic Press Inc., (1995), United States. 13. Sita, L. R., Advances in organometallic chemistry, 38, 189, Academic Press Inc., (1995), United States 14. Zuckerman, J. J., Organotin Compounds: New Chemistry and Applications, American Chemical Society: (1976), United States