GB1579410A - Triorganotin compounds and method for combating insects using same - Google Patents

Description

(54) NOVEL TRIORGANOTIN COMPOUNDS AND METHOD FOR COMBATING INSECTS USING SAME (71) We, M & T CHEMICALS INC., a corporation organised and existing under the laws of the State of Delaware, United States of America, with executive offices at 22 Gate House Road, Stamford, Conneticut, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- While tri-n-alkyltin compounds, compounds wherein the hydrocarbon radical contains I to 4 carbon atoms particularly tri-n-butyltin derivatives, have insecticidal properties, these compounds are insufficiently selective toward plant crops since, while the insect attacking the plant may be controlled, the plant to which the compound is applied is often killed or severely damaged.

It has now been found that a novel class of tri(sec-alkyl)tin compounds effectively control insects which attack agricultural crops, yet do not seriously damage the plants at the use levels required to control these insects.

The invention provides a tri(sec-alkyl)tin compound of the general formula

wherein each of R' and R2 is a linear or branched-chain alkyl group containing I to 4 carbon atoms with the proviso that the total number of carbon atoms in R' and R2 is 4 to 7, Y is chlorine, bromine, iodine, fluorine, hydroxyl, cyanide, carbamate, thiocarbamate, dithiocarbamate, cyanate, thiocyanate, nitrate, phenoxy, enolate, -NH2,

SR3, OR4, oxygen, sulphur, sulphate, carbonate, phosphate, or dialkyl dithiophosphate, wherein R3 is an alkyl group containing I to 12 carbon atoms or a phenyl group, R4 is an alkyl group containing I to 12 carbon atoms, a is the valence of Y and is integers 1,2 or 3, and n is an integer in the range of I to 6 inclusive.

R' in the above formula may be methyl and R2 n-propyl or isopropyl or RX may be ethyl and R2 ethyl, n-propyl or isopropyl.

Tri-(sec-alkyl)tin halides of the above formula wherein the halogen is chlorine, bromine or iodine may be prepared by reacting at least three moles of the corresponding sec-alkyl magnesium halide,

per mole of an alkyltin trihalide RSnZ32, in which R is a linear alkyl radical containing one to eight carbon atoms.

The resultant tetraorganotin compound,

is then reacted with an equimolar amount of a stannic halide, SnZ43. During the reaction the alkyl residue R present in the tetraorganotin compound is replaced by a halogen atom from the stannic halide. In these formulae Z1, Z2 and Z3 represent chlorine, bromine or iodine.

The aforementioned alkyltin trihalide RSnZ3 can be prepared by reacting the corresponding alkyl halide, RZ', with a stannous halide SnZ2 as described in United States Patent No. 3,340,283.

The reaction between the stannic halide and the asymmetric tetraorganotin compound should be performed under anhydrous conditions at a temperature of -25 to 800C., preferably +25 to 800 C., in a hydrocarbon solvent, such for example as pentane, hexane, cyclohexane or benzene.

The stannic halide is dissolved in the organic solvent and the resultant solution is added dropwise to a solution of the tetraorganotin compound in the same solvent. The temperature of the reaction mixture is preferably maintained below 30"C. during the addition, which requires about one hour, after which the mixture is heated to a temperature from 35 to 800C. The temperature conveniently employed is the boiling point of the reaction mixture. Heating is continued for 15 to 60 minutes to ensure complete reaction. The reaction mixture is then allowed to cool to ambient temperature, and extracted with one or more portions of water or aqueous mineral acid. The by-product of the reaction, a mono-organotin trihalide, RSnZ3, is soluble in aqueous media. The desired product remains in the organic phase, and is readily isolated by boiling off the hydrocarbon solvent. No further purification is usually required, however the product can be distilled if desired. The organic layer is freed of any dissolved water following the extraction step. Any of the conventional chemical dehydrating agents are suitable, provided that they will not react with either the triorganotin halide or the hydrocarbon solvent. Preferred dehydrating agents are anhydrous magnesium sulphate, anhydrous sodium sulphate and anhydrous calcium sulphate.

The triorganotin halides so obtained are liquids at ambient temperature. They can readily be converted to other derivatives such as the oxide, acetate and sulphate using known reactions. Other anionic radicals can be introduced by reacting the corresponding triorganotin halide, hydroxide or bis(triorganotin) oxide with the reagents indicated in the following table.

ORGANOTIN DERIVATIVE +REAGENT < DESIRED PRODUCT Chloride, Bromide Carboxylic acid carboxylate, or Iodide + acid acceptor, e.g. acetate e.g. pyridine alkali metal salt of a carboxylic acid aqueous solution of oxide (or alkali metal hydro hydroxide) xide Alkali metal alk- alkoxide oxide or alcohol + acid accepter (e.g.

an amine) alkali metal phen- phenoxide oxide or phenol + acid accepter potassium fluoride fluoride or hydrofluoric acid alkali metal sulphide sulphide alkali metal sulphate sulphate mercaptan + acid mercaptide accepter alkali metal cyanate cyanate alkali metal thiocyanate thiocyanate Alkali metal thiocarbamate thiocarbamate alkali metal dithiocarbamate dithiocarbamate Chloride, Bromide phosphoric acid phospate or Iodide or alkali metal phosphate alkali metal dialkyldithio dialkyldithio- phosphate phosphate Oxide or Hydroxide carboxylic acid or carboxylate anhydride alcohol (or phenol) alkoxide (or phenoxide) hydrofluoric acid fluoride dilute (10--25 weight sulphate %) aqueous sulphuric acid ORGANOTIN DERIVATIVE + REAGENT < DESIRED PRODUCT hydrogen sulphide sulphide alkyl or aryl mercaptide mercaptan carbon dioxide carbonate Hydroxide heat to remove oxide water The reaction conditions such as preferred solvents, temperatures and reactions times for preparing the derivatives summarized in the preceding table are known. A comprehensive treatment of this subject matter together with numerous literature references is contained in an article by R. K. Ingham et al. in the October, 1960 issue of CHEMICAL REVIEWS (pp.459-539). The derivatives are liquids or solids at ambient temperature, depending upon the type of substituents represented by Y.

The tri(sec-alkyl)tin compounds according to the invention effectively control many types of undesirable insects when applied to living plants that are susceptible to infestation by these insects. They are particularly effective against insects of the order homoptera, including aphids, and the larval stage of the order lepodoptera, which includes the cabbage looper, corn borer and the bollworm larva. Some of the compounds effectively control the two-spotted spider mite (Tetrancychus bimaculatus). A single application of these compounds to living plants or other substrates can provide residual and extended control of many varieties of insects for a considerable period of time, the duration of which is dependent to some extent upon mechanical and biological influences, including weather. Formulations containing the present organotin compounds can be applied directly to the insect to be controlled.

In preparing compositions for application to plants the organotin compound is often augmented or modified by combining it with one or more commonly employed pesticide additives or adjuvants including organic solvents, water or other liquid carriers, surfactants to aid in dispersing or emulsifying the organotin compound or particulate and finely comminuted or divided solid carriers.

Depending upon the concentration of triorganotin compound in these compositions, they can be employed either without additional dilution or as liquid concentrates which are subsequently diluted with one or more inert liquids to produce the ultimate treating compositions. In compositions employed as concentrates, the triorganotin compound can be present at concentrations of 5 to 98% by weight. Other biologically active agents that are chemically compatible with the triorganotin compounds can also be added.

The optimum effective concentration of tin compounds to be employed as toxicant in a composition is dependent upon whether the insect is contacted with or ingests the toxicant. The actual weight of compound constituting an effective dose is primarily dependent upon the susceptibility of a particular insect to a given triorganotin compound. For control of the cabbage looper (Trichoplusia ni), good results are obtained with liquid or dust compositions containing 25 to 1000 parts per million by weight of toxicant. Compositions containing up to 90 percent by weight of toxicant can be employed to treat a heavily infested area.

In the preparation of dust compositions, the organotin compound can be blended with many commonly employed finely divided solid carriers such as fuller's earth, attapulgite, bentonite, pyrophillite, vermiculite, diatomaceous earth, talc, chalk, gypsum and wood flour. The carrier, usually in a finely devided form, is ground or mixed with the toxicant or wetted with a dispersion of the toxicant in a volatile liquid. Depending upon the relative proportions of toxicant and carrier, these compositions can be employed as concentrates that are subsequently diluted with additional solid carrier to obtain the desired amount of active ingredient.

Alternatively, such concentrate dust compositions can be employed in combination with various known anionic, cationic or non-ionic surfactants as emulsifying or dispersing agents to form spray concentrates. Such concentrates are readily dispersible in liquid carriers to form spray compositions or liquid formulations containing the toxicants in any desired amount. The choice and concentration of surfactant are determined by the ability of the material to facilitate the dispersing of the concentrate in the liquid carrier to produce the desired liquid composition. Suitable liquid carriers include water, methanol., ethanol, isopropanol, methyl ethyl ketone, acetone, methylene chloride, chlorobenzene, toluene, xylene and petroleum distillates. Among the preferred petrolleum distillates are those boiling under 400"F. at atmospheric pressure and having a flash point above 80"F.

Liquid compositions can also be prepared by dissolving one of the triorganotin compounds in a mixture containing a water-immiscible organic liquid and a surface active dispersing agent. The resultant emulsifiable concentrate is then further diluted with water and an oil to spray mixture in the form of an oil-in-water emulsion. Preferred dispersing agents are oil soluble and include the condensation products of alkylene oxides with phenols and organic and inorganic acids, polyoxyethylene derivatives of sorbitan esters, alkylarylsulphonates, complex ether alcohols, and mahogany soaps. Suitable organic liquids to be employed in the compositions include petroleum distillates. hexanol, liquid halohydrocarbons and synthetic organic oils. The surface active dispersing agents are usually employed in the liquid dispersions and aqueous emulsions in the amount of I to 20% by weight of the combined weight of the dispersing agent and the active toxicant.

When operating in accordance with the present invention, the organotin compound or a composition containing the compound can be applied directly onto the undesirable insect or to the site to be protected, particularly plants and trees.

Application to the foliage of plants is conveniently carried out using power dusters, boom sprayers and spray dusters. When employed in this manner the compositions should not contain any significant amounts of phytotoxic diluents. In large scale operations, dusts or low volume sprays may be applied from an aircraft.

In the following examples all parts and percentages are by weight unless otherwise specified.

EXAMPLES.

Example 1.

Preparation of Tri(3-pentyl)tin Chloride A. Preparation of Methyl Tri(3-pentyl)tin To 16 g. (0.66 g. atom) of magnesium turnings maintained at a temperature of 25"C. under a nitrogen atmosphere was added 25 cc. of a solution containing 99.7 g (0.66 mole) of 3-bromopentane dissolved in 300 cc. of anhydrous tetrahydrofuran.

The reaction was initiated using a few drops of ethylene dibromide. The remainder of the 3-bromopentane solution was gradually added in a period of one hour while the reaction mixture was heated to the boiling point. Heating was continued for an additional hour. The reaction mixture was then allowed to cool to ambient temperature, when all of the magnesium appeared to have reacted. The resultant solution contained 0.6 mole of 3-pentyl magnesium bromide, and was added dropwise to a stirred solution of methyltin trichloride (49 g., 0.2 mole) dissolved in 50 cc. of dry benzene. The solution required 0.5 hour and was conducted under a nitrogen atmosphere. During the addition the temperature of the reaction mixture rose to 710C. Following completion of the addition the reaction mixture was heated to the boiling point for one hour, then allowed to cool to ambient temperature. To the resultant mixture was added a solution containing 250 cc.

water and 15 cc. concentrated sulphuric acid over a five minute period. The aqueous phase was separated and the organic phase was combined with a portion of anhydrous magnesium sulphate, which was subsequently removed by filtration.

The solvent was evaporated under reduced pressure to yield 58.8 g (85% yield) of a yellow liquid having a refractive index (n2D) of 1.4954. This product was extracted twice with methanol and distilled under reduced pressure. The fraction boiling from 81 to 870C. under a pressure of 0.15 mm. was isolated and had a refractive index (n2D) of 1.4920. Analysis by vapour phase chromatography indicated that the product was 95.7% pure.

B. Cleavage of Methyl Tri(3-pentyl)tin to Tri(3-pentyl)tin Chloride 20.8 g. (0.06 mole) of the methyl tri(3-pentyl)tin so prepared was dissolved in 50 cc. of pentane. To this solution was added a solution containing 15.6 g. (0.06 mole) of stannic chloride and 50 cc. pentane. The addition required 20 minutes, following which the resultant mixture was heated to the boiling point (400 C.) for 45 minutes and then allowed to cool to ambient temperature. A solution obtained by combining 2 cc. of 12N aqueous hydrochloric acid and 200 cc. water was then added to the reaction mixture with vigorous stirring both during the addition and for three minutes thereafter. The organic layer of the resultant two-phase liquid was isolated and combined with the same aqueous hydrochloric acid solution. The organic layer was isolated and the water removed from it using a quantity of anhydrous magnesium sulphate. The pentane was then evaporated under reduced pressure to yield 21.6 g. of a yellow liquid having a refractive index (n2D) of 1.5060.

Upon analysis the product was found to contain 32.04% tin and 9.42% chlorine.

The calculated values for tri(3-pentyl)tin chloride are 32.29% tin and 9.64% chlorine.

Bis[tri(3-pentyl)tinloxide was prepared by adding a solution of the corresponding chloride (37.4 g. of the chloride in 100 cc. of a solution containing equal volumes of methanol and ethanol) to a solution containign 16.0 g. of sodium hydroxide, 50 cc. water and 50 cc. methanol. The addition was gradual and required 15 minutes. The resultant cloudy solution was heated to the boiling point for 15 minutes, after which it was allowed to cool to ambient temperature. 400 cc.

of water followed by 300 cc. of diethyl ether were added while the mixture was vigorously stirred. The ether layer of the resultant two-phase liquid was freed of water using anhydrous magnesium sulphate, after which the drying agent was removed and the ether evaporated by heating the mixture under reduced pressure.

The residual yellow liquid weighed 34.9 g. and was found to contain 34.62% tin and no chlorine. Pure bis[tri(3-pentyl)tin]oxide contains 34.95% tin. Analysis by potentiometric titration indicated that the oxide was 93.4% pure.

Example 2.

Preparation of Tri(2-pentyl)-, Tri(3-hexyl)-and Tris(4-methyl-2-pentyl)tin Chlorides and Oxides.

Each of the above compounds was prepared from the corresponding methyl tri(sec-alkyl)tin compound by the procedure described in Example 1. The reagents employed and the properties of the intermediate tetraorganotin compound, chloride and oxide are set forth in the following tables.

The aforementioned intermediate tetraorganotin compounds were prepared in the usual manner from methyltin trichloride and the corresponding Grignard reagent in the quantities shown below.

TABLE I Preparation of Tetraorganotin Compounds Product Grignard Reagent Moles MeSnCl3 Prod. Wt.

(g.) Methyltri(2-pentyl)tin 2-Pentyl MgBr 1 72 68.9 g.* Methyltri(3-hexyl)tin 3-Hexyl MgBr 1 72 69;8 g.* Methyltri(4-methyl-2-pentyl)tin 4-Me thy I-2-pentyl 1 72 73.3 g.* MgBr * following distillation TABLE II Properties of Tetraorganotin Compounds Intermediate Found Theory Assay B.P. &commat; Pressure Compound % Sn % Cl % Sn % Cl VPC % (mm. of Hg.) TID Methyltri 34.28 0.12 34.19 0.0 96.2 88-92 &commat; 0.07 1.4835&commat;210C.

(2-penty 1) tin Methyltri 30.25 0.65 30.50 0.0 93.6 107-114 &commat; 0.4 1A904&commat;190C.

(3-hexyl)tin Methyltri 29.28 0.11 30.50 0.0 95.1 103-107 &commat;0.15 1.4765&commat;26 C (4-methyl-2- pentyl)tin TABLE III Preparation of the Tri(sec-alkyl)tin Chlorides Product Final Product Intermediate Weight SnCl4Wt. Weight (g.) Tri(2-pentyl)tin Methyltri(2-pentyl)tin 2D.8 15.6 21.4 g.

chloride Tri(3-hexyl)tin Methyltri(3-hexyl)tin 68.1 45.6 70.6 g.

chloride Tri(4-methyl- Methyltri(4-methyl 71.6 47.9 74.6 g.

2-pentyl)tin 2-penty I) tin chloride TABLE 4 Properties of the Tri(sec-alkyl)tin Chlorides Found Theory Assay % Sn %Cl % Sn %Cl VPC % 71D Tri(2-pentyl)tin Chloride 32.24 9.28 32.29 9.65 95.6 1.4956 0 250C.

Tri(3-hexyl)tin Chloride 28.94 8.67 28.97 8.65 95.9 1.5005 &commat; 210C.

Tri(4-methyl-2-pentyl)tinChloride29.02. 8.70 28.97 8.65 94.2 1.4900 &commat; 230C.

The organotin chlorides shown in Table 4 were converted to bis-oxide derivatives in a manner essentially similar to that described above for bis(tri-3-pentyl)tin oxide.

Properties of these materials are shown in Table 5 below.

TABLE 5 Properties of Bistri(sec-alky1)tin} oxides Found Theory Assay* Product % Sn NO Cl % sun % Bisttri(2-pentyl)tin} oxide 34;58 0 34.95 0 99.6 1.5000 &commat; 210C.

Bis[tri(3-hexyl)tin] oxide 30.90 0.01 31.06 0 99.5 1.5028 &commat; 220C.

Bis[tri(4-mthyl-2- 30.89 0 31.06 0 100 1.4914 &commat; 220C.

pentyl)tinl oxide * by potentiometric titration Example 3.

Biological Activity of Tri(sec-alkyl)tin Compounds The efficacy of five of the compounds disclosed in the foregoing examples in controlling a number of undesirable insects was evaluated using one or more of the test procedures summarized hereinafter.

Test Procedures.

A. The insect is placed in an aqueous dispersion containing a specified concentration of the organotin compound. Contact time is two seconds. The larvae were then set aside for six days, at which time the percent mortality was observed.

B. A bean plant is sprayed with an aqueous dispersion containing a specified concentration of organotin compound. The test insect is placed on the treated foliage and remains undisturbed for three days, at which time the percent mortality is observed.

C. A bean plant infested with the insect is sprayed and remains undisturbed for three days, at which time the percent mortality is observed.

D. Five third instar bollworm larvae are placed in petri plates containing a layer of semi-synthetic diet. These larvae are sprayed with 3 cc. of a solution or suspension containing 400 parts per million (ppm) of the chemical. The spraying is accomplished from a distance of 15 inches (38 cm.) using a Spraying Systems Company nozzle type 40100-120. After spraying, the petri dish cover is replaced with a fiber brewer lid to permit limited air exchange. A mortality count is taken following a holding period of up to three days.

The concentrations of active compound in the following tables are expressed in parts per million (ppm) of total dispersion.

TABLE 6.

Activity Against Cabbage Looper (Trichoplusia ni) %mortality &commat; x ppm Compound Procedure of compound x=400 100 Tri(3-hexyl)tin chloride A 100 80 B 100 100 Bis[tri(3-pentyl)tin] oxide A 100 100 B 100 100 Bis[tri(2-pentyl)tin] oxide A 100 100 B 100 0 Bis[tri(4-methyl-2-pentyl)tin] oxide A 100 100 B 100 100 Bis[tri(3-hexyl)tin] oxide A 100 100 B 100 100 TABLE 7 Activity Against Aphids Using Procedure C Compound % mortality &commat; 100 ppm of Compound Tri(3-hexyl)tin chloride 100 Bisltri(3-pentyl)tin] oxide 100 Bis[tri(4-methyl-2-pentyl)tin] oxide 100 Bis[tri(3-hexyl)tin] oxide 100 TABLE 8 Activity Against Bollworm Larvae (Heliothis zeae) Using Procedure D % mortality &commat; 400 ppm Compound of compound Tri(3-hexyl)tin chloride 80 Bis[tri(3-pentyl)tin] oxide 80 Bis[tri(2-pentyl)tin] oxide 60 Bis [tri(4-methyl-2-pentyl)tin] oxide 60 Bis[tri(3-hexyl)tin] oxide 100 TABLE 9 Activity Against Two-Spotted Spider Mite Using Procedure C With Tricyclohexyltin Hydroxide As A Control % mortality Compound rate (ppm compound) 400 200 100 50 25 12.5 Bis[tri(3-pentyl)tin] oxide 99 99 96 95 94 38 Tricyclohexyltin hydroxide 100 100 99 98 55 0 The foregoing data demonstrate that at concentrations below 50 parts per million the present compounds are superior to tricyclohexyltin hydroxide, a commercial miticide. At a level of 25 parts per million bis[tri(3-pentyl)tin] oxide was almost twice as efficacious as the control. In practical terms, this means that less of the present compounds are required to effectively control spider mites relative to present commercially available triorganotin compounds.

WHAT WE CLAIM IS: 1. A tri(sec-alkyl)tin compound of the formula

wherein each of R' and R2 is a linear or branched-chain alkyl group containing I to 4 carbon atoms with the proviso that the total number of carbon atoms in R' and R2 is 4 to 7, Y is chlorine, bromine, iodine, fluorine, hydroxyl, cyanide, carbamate, thiocarbamate, dithiocarbamate, cyanate, thiocyanate, nitrate, phenoxy, enolate, -NH2,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   TABLE 8 Activity Against Bollworm Larvae (Heliothis zeae) Using Procedure D % mortality &commat; 400 ppm Compound of compound Tri(3-hexyl)tin chloride 80 Bis[tri(3-pentyl)tin] oxide 80 Bis[tri(2-pentyl)tin] oxide 60 Bis [tri(4-methyl-2-pentyl)tin] oxide 60 Bis[tri(3-hexyl)tin] oxide 100 TABLE 9 Activity Against Two-Spotted Spider Mite Using Procedure C With Tricyclohexyltin Hydroxide As A Control % mortality Compound rate (ppm compound)

   400 200 100 50 25 12.5 Bis[tri(3-pentyl)tin] oxide 99 99 96 95 94 38 Tricyclohexyltin hydroxide 100 100 99 98 55 0 The foregoing data demonstrate that at concentrations below 50 parts per million the present compounds are superior to tricyclohexyltin hydroxide, a commercial miticide. At a level of 25 parts per million bis[tri(3-pentyl)tin] oxide was almost twice as efficacious as the control. In practical terms, this means that less of the present compounds are required to effectively control spider mites relative to present commercially available triorganotin compounds.

   WHAT WE CLAIM IS: 1. A tri(sec-alkyl)tin compound of the formula

   wherein each of R' and R2 is a linear or branched-chain alkyl group containing I to 4 carbon atoms with the proviso that the total number of carbon atoms in R' and R2 is 4 to 7, Y is chlorine, bromine, iodine, fluorine, hydroxyl, cyanide, carbamate, thiocarbamate, dithiocarbamate, cyanate, thiocyanate, nitrate, phenoxy, enolate, -NH2,

   SR3, OR4, oxygen, sulphur, sulphate, carbonate, phosphate, or dialkyl dithiophosphate, wherein R3 is an alkyl group containing 1 to 12 carbon atoms or a phenyl group, R4 is an alkyl group containing I to 12 carbon atoms, a is the valence of Y and is integers 1, 2 or 3, and n is an integer in the range of 1 to 6, inclusive.
2. 2. A tri(sec-alkyl)tin compound as claimed in claim I, werein R' is methyl and R2 is n-propyl or isopropyl or wherein R' is ethyl and R2 is ethyl, n-propyl or isopropyl.
3. 3. A tri(sec-alkyl)tin compound as claimed in claim 1, wherein Y is chlorine.
4. 4. A tri(sec-alkyl)tin compound as claimed in claim 1, wherein Y is oxygen.
5. 5. A tri(sec-alkyl)tin compound as claimed in claim 1, which is selected from tri(3-hexyl)tin chloride, bis[tri(3-pentyl)tin]oxide, bis[tri(2-pentyl)tin]oxide, bis [tri(4-methyl-2-pentyl)tin] oxide and bis[tri(3-hexyl)tinloxide.
6. 6. A composition for controlling insects by application of the composition to the insects or to living plants, said composition comprising an inert liquid or inert solid carrier and an insecticidally effective amount of a tri(sec-alkyl)tin compound as claimed in any one of the preceding claims I to 5.
7. 7. A composition as claimed in claim 6, wherein the tri(sec-alkyl)tin compound is present at a concentration of 25 to 1000 parts by weight per million parts of the composition.