3,499,887 United States Patent Office Patented Mar. 10, 1970 2 tained from a divalent metal such as zinc, cadmium and 3,499,887 POLYMERIZATION CATALYSTS FOR copper with ethane dithiol (i.e. R1 is a di-methylene EPSULPHOES group and Y is sulphur) or bis (beta-mercaptopropyl) Wilfrid Cooper, Aldridge, George Vaughan, Sutton Cold Sulphide (i.e. R1 is -CHCH (CH) SCH(CH) CH field, and Reginald T. Wragg, Tamworth, England, as and Y is Sulphur). In the case where R contains an atom signors to The Dunlop Company Limited, London, which is associated with the metal as by means of a co England, a British company ordination bond (->), the compounds can be represented No Drawing. Filed Apr. 28, 1967, Ser. No. 634,476 by the general formula Claims priority, application Great Britain, May 13, 1966, 21,239/66 S Hnt. C. C07d 23/00; C07f 3/06, 3/08 10 U.S. C. 260-239 4 Claims Z. -(^^ Y. ) where A is equal to 0, 1, 2 . . . . (Az--B-1), Az--B ABSTRACT OF THE DISCLOSURE where B is an integer greater than 0, X represents a group 15 containing an atom such as nitrogen, oxygen, sulphur or Organometallic compounds suitable as catalyst for the phosphorus capable of forming a co-ordination bond polymerization of episulphides, in which at least one of with the metal and RX is equivalent to R. Particularly the valency states of the metal is satisfied by the grouping Suitable catalysts of this type are compounds in which Ais -SR where R represents an organic radical containing 0 and B is 2 and M is a divalent metal i.e. compounds of at least one other atom which is chemically bonded to 20 general formula the metal or which is associated with the metal by means of a co-ordination bond, are prepared by reacting a salt X S of the metal with the appropriate thiol compound. R? YM/ Y, N/ R / S X 25 This invention relates to the polymerization of episul The group X in the above general formula may be phides. for example an -OR2 group, an -SR3, an -NCRRs) The present invention provides organometallic com group or a P(R6Rf) wherein said groups R2, R, R R5, pounds suitable as catalysts for the polymerization of R6 and R7 represent hydrogen atoms, alkyl groups, cyclo episulphides, in which one or more of the valency states 30 aliphatic groups, aryl or aralkyl groups. The simplest of the metal are satisfied by the grouping-SR where R compounds of this type are those in which X represents represents an organic radical containing at least one a hydroxyl group or an amino group. These simple other atom which is chemically bonded to the metal compounds are generally insoluble in the episulphide or which is associated with the metal by means of a monomer or monomers to be polymerized and in most co-ordination bond. (Hereafter these compounds will be 35 common solvents. However, by substituting alkyl or referred to as “catalysts.") other hydro-carbon groupings onto the nitrogen, sulphur The present invention also provides a method for the or other co-ordinating atom, the compounds can be made polymerization of one or more episulphides which com Soluble in the monomer or monomers to be polymerized prises contacting the episulphide or episulphides with or in the solvent and these soluble catalysts are partic these organometallic polymerization catalysts. 40 ularly useful in that they enable control to be exercised Particularly suitable catalysts are compounds. in which over the molecular weight of the resulting polymers. Par the metal has a co-ordination number of 4, 5 or 6 in ticularly preferred, are compounds in which X is complexes with ligands containing sulphur and/or other -NRRs where one or both of R and R5 are the same donor atoms. Examples of such metals are zinc, cadmium, or different alkyl groups having 1 to 4 carbon atoms. copper, silver and nickel but certain other metals, e.g. 45 Examples of Suitable catalysts of this type are the com lead can also be employed. The particularly preferred plexes obtained from a metal salt and, for example, beta catalysts are those which contain zinc or cadmium as the aminoethane thiol, (gem-dimethyl) beta-aminoethane thiol metal. Not all the valency states of the metal need be (i.e. R1 is -CH2C(CH3)2-) or beta-mercapto etha satisfied by the chemical bonds to the -SR grouping as no ethanol (i.e. Ri is -CH2CH2-) N-n-butylaminopro described above. The catalysts have the general struc 50 pane-2-thiol or N-di-n-butyl aminopropane-2-thiol (i.e. ture ZA-M-(S-R) where M is the metal, Z is an R1 is -CH2CH(CH3) -). The last two named com anion such as Cl, CH3COO or CO - and A is equal pounds are catalysts which are soluble in the monomer(s) to 0, 1, 2 . . . (Az--By-y), (Az--By), where z is the or in hydrocarbon solvents. valence of the anion and y is the number of atoms or For convenience most of the structural formula are groups in the -S-R grouping which are chemically 55 depicted in the monomeric form in which the group X bonded to the metal M. The group R of the polym or Y is linked to the same metal atom as the sulphur. erization catalyst can be an aliphatic cycloaliphatic, Analytical and molecular weight data generally support heterocyclic, aryl or aralkyl radical but must contain a these structures. It is possible, however, for more than second atom or grouping which is either bonded or co one metal atom to be attached in the complex and thus ordinated to the metal atom M. In the case where R con 60 result in dimeric and higher polymeric structures such as tains an atom or grouping, Y, such as S or COO, which s-R-Y YMSR 1. is chemically bonded to the metal M, such compounds ZAM M. Z.A or - ra can be represented by the general formula / ZA Y-R-S S / N 65 The polymerization catalysts can be prepared by re ZA-M R acting a salt of the metal such as the oxide, chloride or () ) acetate of the metal with the appropriate thiol compound in which A is equal to 0, 1, 2 . . . (Az--2B-2), preferably in the presence of an acid-acceptor. The thiol Az--2B where B is an integer greater than 0 and is usually compound must contain in addition to the thiol group a equal to 1, and RY is equivalent to R. Examples of suit 70 further atom which can become bonded directly or by able catalysts of this formula are the compounds ob means of a co-ordination bond to the metal. This further 3,499,887. 3 4. atom can be for instance a sulphur atom in the form of a mercaptains, in the reaction mixture is detrimental to the second thiol group to yield catalysts of formula control of molecular weight by catalyst concentration and when high molecular weight polymers are required they should be rigidly excluded. Mercaptans or compounds which can react with the 3. episulphide to yield mercaptans, such as for example As described hereinbefore they may also be dimeric or amines, can be used as transfer agents. Added in con polymeric in structure. In the case where the catalyst con trolled amounts they result in a lowering of the molecular tains an atom which co-ordinates with the metal rather weight of the polymer without any change in rate of than becomes directly bonded then the metal salt is re O polymerization. The amount to be added to produce a acted with for example an amine-thiol given molecular weight will of course depend upon the nature of the mercaptan used and on the amount of catalyst used. or an ether thiol (RO-R-SH). Usually in this case It is believed that the polymerization catalyst is in two moles of the amine-thiol or ether-thiol will react with corporated into the growing polymer chain and provides one mole of the salt of a divalent metal. the active centre at which growth of the polymer chain The reaction between the metal salts and the thiol occurs. Growth of the polymer chains continues until compounds to prepare the catalysts can conveniently be all the available monomer has been polymerized and the carried out at room temperature (10 to 30° C.) simply resulting polymer chains contain the active centre pro by mixing the reagents in the presence of an acid ac vided by the catalyst incorporated therein. This active ceptor such as sodium hydroxide, Sodium bicarbonate, Or centre is stable and even after a period of several weeks ammonia, and stirring the mixture. The catalysts are addition of a further amount of monomer to the polym stable and can be stored for several weeks prior to use. erization reaction mixture will result in polymer-chain The amount of the metal salt and the thiol compound growth to increase the length of the existing polymer used can vary considerably but the molar ratio of the 25 chains. The present invention therefore provides a method metal salt to the thiol will preferably be from 1:1.5 to of making block copolymers of episulphides since the 1:2.5, usually 1:2 especially with zinc and cadmium salts. monomer added to an existing polymer containing an The polymerization of one or more episulphides using active centre may be a different monomer to that initially the catalysts can be carried out in the bulk phase or if added to the catalyst. desired in the presence of an organic solvent for the 30 The polymerization reaction is difficult to terminate episulphide or episulphides to be polymerized. Examples and it has been found that polymer chain growth cau of suitable solvents are the liquid hydrocarbons, such as continue even after the addition to the polymerization hexane and benzene, certain halogenated solvents such reaction mixture of a mixture of acid and alcohol. Thus as halogenated hydrocarbons, e.g. chloroform, and a large the polymerization activity is usually terminated only on excess of the solvent may be used. Alternatively the removal of the catalyst from the polymer chains. This polymerization can be effected by an emulsion or Sus removal of catalytic activity from the polymer can be pension polymerization technique in which the reaction is effected by adding a low molecular weight thiol com carried out in the presence of a non-solvent for the epi pound to the polymerization reaction mixture. When sulphide or episulphides such as water, which may prefer all the monomer has been converted to polymer, the ably contain an emulsifying agent or a dispersing agent 40 metal will be removed from the polymer and precipitated (e.g. polyvinyl alcohol). as an insoluble compound with the thiol compound which The polymerization reaction can be carried out at a can be removed by filtration if necessary. temperature of from - 50° C. to 150° C. Room tempera As stated hereinbefore, particularly suitable catalysts ture (10 to 30° C.) can be employed for convenience. are those containing two (-S-R) groupings attached The reaction begins immediately upon contact of the to the same metal atom particularly a divalent metal and monomer or monomers with the catalyst and depending in which the R grouping also contains a co-ordinating upon the particular catalyst may take from 1 hour to 30 group X i.e. catalysts of the general monomeric form. hours to reach completion. Substantially complete con X S / Y / N version of monomer to polymer is obtained. R. M. R1 The shape of the conversion time curve depends upon N / N / the metal and the particular thiol chosen for the forma S X tion of the catalyst complex. Other things being equal Such catalysts result in growth of two polymer chains cadmium complexes generally give shorter induction simultaneously, and removal of the metal from the periods than zinc compounds. The induction period may polymer results in polymers of molecular weight approxi also be reduced by use of a catalyst which does not form mately one half of the molecular weight of the growing the more stable 5 or 6 membered rings in the initial com polymers. Also, removal of the metal will result in the plex since in the latter the insertion of the first monomer production of a terminal thiol group oa each of the unit usually occurs at a slower rate than the subsequent polymer molecules. propagation steps. Rapid initiation is obtained from the Also of particular importance in producing polymers cadmium mercaptide of 1,2-dimethyl-2'-diethylamino-2- 60 of mercaptain functionality of two or more are those mercapto-diethyl-sulphide catalysts which are formed in such a way that they con tain two or more sulphur atoms attached to the same (Etn. CHCH (CH) S. CHCH (CH)SH) metal atom and to the same R grouping i.e. catalysts of which forms an eight membered ring in the initial the structure complex. 65 S The molecular weight of the resulting polymers may / N vary over a wide range and is controlled by the amount R M-ZA and solubility characteristics of the catalyst. As herein Ys/ before stated the use of soluble catalysts enables a greater degree of control to be exercised over the molecular 70 in their simplest form particularly those from the divalent weight of the resulting polymer. Zinc or cadmium The amount used of the catalyst is dependent upon the S desired molecular weight of the polymer to be produced, / N being greater the lower the desired molecular weight of RM the polymer. The presence of certain impurities, especially 5 S 3,499,887 5 6 and those where several sulphur atoms are attached to The procedure of Experiment No. 1 was again repeated the same R1 grouping but perhaps to different metal atoms (Experiment No. 3) except that the N-dibutylaminopro i.e. catalysts of the general form pane-2-thiol was replaced by an equimolar amount of N-monobutyl-aminopropane-2-thiol. The product could be crystallized as needles from chloroform. This product Ys/ N s^ was analysed the analysis corresponding to the formula: CH-NH-CH-CH (CH) SZn in their simplest form. In these catalysts the grouping R1, O may also contain an atom which co-ordinates to the metal CH-NH-CH (CH). CHSJZn M but these bonds are not depicted in the formula. O The polymerization process of the present invention EXAMPLE II can be used to effect the polymerization of a wide variety of episulphides. Aliphatic, cycloaliphatic or aromatic This example illustrates the preparation of catalysts episulphides can be polymerized, as can mono-episul containing cadmium as the metal. phides and episulphides containing more than one episul 15 The procedure outlined in Experiment No. 2 of Ex phide group. Examples of suitable episulphides are ample I was employed to react N-monobutylaminopro aliphatic and cycloaliphatic mono- and diepisulphides pane-2-thiol with cadmium acetate. The reagents were such as ethylene sulphide, propylene sulphide, pentene used in the amounts given in Example I. The product was episulphides, hexadiene mono- and diepisulphides, cyclo a solid which was soluble in hydrocarbons. The solid was hexene episulphide, cyclopentadiene diepisulphide and 20 not readily crystallised. Analysis of the product indicated decatriene triepisulphides. Aromatic episulphides such as the formula: styrene episulphide may be polymerized. The episulphides CH-NHCH2CHCCH) SCd may if desired contain substituents attached to the carbon O atoms of the molecular chain. Those polymers having a mercaptain functionality of CH-NH-CH(CH). CHSJCd two or more can be cured by heating with a curing agent The above procedure was again repeated, but using such as lead oxide in the presence of a small amount of N-dibutylaminopropane -2-thiol instead of the monobutyl a trifunctional thiol compound or by treating with other derivative. The product was a viscous oil, the analysis of reagents which are reactable with two or more of the which indicated the formula mercaptan groups such as activated dienes e.g. divinyl 30 CHg). N. CH-CH (CH) SiCd sulphone, diisocyanates e.g. toluene diisocyanate and di O epoxides. (CAH).N. CHCCH). CHSCd The polymers can be used for coatings, adhesives and, laminates and in applications where oil resistance is im EXAMPLE III portant. This example illustrates the preparation of further cata The invention is illustrated by the following examples. lysts containing zinc as the metal. In the examples, the hydrated zinc acetate has the A complex of beta-aminoethane thiol and zinc was formula, Zn(OAc)2.2.5H2O. prepared by the procedure outlined in Experiment No. 1 of Example I, using beta-aminoethane thiol instead of EXAMPLE I 40 the dibutylaminopropane-2-thiol. This example illustrated the preparation of catalysts containing zinc as the metal. The product was a quantitative yield of a crystalline 42.0 gms. of N-dibutylaminopropane-2-thiol were added solid, analysis of which indicated the formula: to a solution of 10 gms. of sodium hydroxide in 200 mls. (H.N. CHCHS)Zn of water. Sufficient ethanol was then added to cause com 45 The procedure of Experiment No. 1 of Example I was plete dissolution of the amine-thiol. A solution of 130 again repeated but this time using (gem-dimethyl) beta gms. of zinc chloride in 40 mls. of water was slowly added aminoethane thiol as the thiol compound. The product to the mixture which was vigorously stirred throughout was a crystalline solid obtained in quantitative yield of the addition. Stirring was continued after the addition formula: of the zinc chloride and after 1 hour at room temperature 50 the resulting mixture containing a viscous oil was ex tracted several times with ether. The ether solution was dried over magnesium sulphate and was then concen trated by evaporation. The resulting viscous residue was EXAMPLE IV then dried under vacuo (0.01 mm. Hg) at 70-80 C. This example illustrates the preparation of a catalyst for 3 hours. This preparation was denoted as Experiment containing an oxygen atom. No. 1. The procedure of Experiment No. 1 of Example I was The residue was then analysed, and the analysis corre used to react beta-hydroxyethane thiol (beta-mercapto sponded to a formula of: ethanol) and zinc chloride. The product was obtained in (C4H9 ) 2.N.CHCH (CH3 ) S} 2Zn 60 quantitative yield and was a viscous oil which slowly set to a brittle mass. Analysis of the product indicated the O formula: (C4H9) 2.N.CH (CH3 ) ..CH2S) 2Zn (HOCH2CHS)Zn The molecular weight of the complex and its infrared 65 spectrum are in agreement with the above structural EXAMPLE V formulae. The complex was obtained in quantitive yield. This example illustrates the preparation of catalysts In a further experiment (Experiment No. 2) using the from dithiols. above reagents in the same quantities, the powdered zinc Ethane dithiol and zinc chloride were reacted together chloride and the amine-thiol were mixed together for 30 by the procedure of Experiment No. 1 of Example I to minutes, and the other reagents were then added. After a yield a product of formula: further 30 minutes the product was neutralized with sodi CH-S um bicarbonate, extracted with ether and isolated as de scribed above. The product was the same as described / above and it was again obtained in quantitative yield. 75 CH-S 3,499,887 7 8 By the same procedure bis(beta-mercaptoisopropyl) To a solution of 0.12 mole of cadmium acetate dihy drate in methanol was added 0.2 mole of N-dibutyl sulphide and zinc chloride were reacted together to yield aminopropane-2-thiol. After standing for 5 hours, 5 ml. a product of formula: of ammonia (density=0.880) was added with shaking. S. CHCH (CH3).S. CH(CH3). CFI.S After 16 hours an excess of ammonia was added drop Zn 5 wise with vigorous stirring and the mixture was then EXAMPLE VI poured into an excess of water. The viscous oil was dis Each of the products from Examples I to V was used solved in benzene and this solution was passed several to polymerize propylene sulphide by the following pro times through a short column packed with molecular cedure. 2 percent by weight based on the propylene Sul 0 sieve (Union Carbide 4A). The remaining benzene was phide of the catalyst was added to propylene sulphide then removed by freeze-drying to leave a highly viscous in a bottle which was then sealed. The bottle was tumbled oil, which was the cadmium mercaptide of N-dibutyl end over end for 24 hours at room temperature, after aminopropane-2-thiol. M.wt. (calc.) 516 M.wt. (found) which time the percentage conversion of monomer to 518 (Analysis.-Found (percent): C, 49.9; H, 9.2; N, polymer was determined approximately. 5 4.9; S, 12.9; Cd, 22.3. Calc. (percent): C, 51.1; H, 7.4; In all cases except where the catalyst prepared from N, 5.4; S, 12.4; Cd, 21.7). (gem-dimethyl)-beta aminoethane thiol was used the per For storage, the catalyst was made up as a standard centage conversion of monomer to polymer was greater solution in benzene (2.74 g./100 ml.). than 75 percent. In the exception it is believed that polym Catalyst solution was added to purified propylene sul erization was slow due to steric hindrance effects. 20 phide monomer and the mixture was allowed to react The catalysts from Examples I and II were soluble in for 72 hours at 30° C. when polymerization was essen the propylene sulphide. tially complete. EXAMPLE VII EXAMPLE VIII This example demonstrates the control of molecular 25. This example describes the preparation of silver, cop weight which can be achieved by varying the concen per, lead and nickel complexes of N-dibutylaminopro tration of catalyst and/or the conditions of polymeriza pane-2-thiol together with their use as catalysts for the tion, the catalyst in this case being cadmium bis (N-di preparation of polypropylene sulphide. butylamino-propane-2-mercaptide) prepared as in Exam ple II unless otherwise stated. 30 (a) Silver complex of N-dibutylaminopropane-2-thiol The molecular weights obtained depend on the purity To a solution of silver nitrate (8.5 gm.) in water (50 of the monomer and the catalyst as well as on the con ml.) was added 0.880 ammonia (10 ml.) followed by the centration of catalyst. Thus traces of mercaptain in the amino thiol (10.0 gm.). After shaking the mixture for monomer or secondary amine in the catalyst will reduce 1 hour, the precipitate was filtered off, washed with water the molecular weight, the former by transferring growing 35 and methanol and dried in vacuo. Crystallisation from chains from the metal complex and the latter after petroleum spirit (B.P. 60-80) afforded small yellow conversion into a mercaptain by reaction with the mon needles M.P. 97-98. omer. In attempts to prepare polymer of molecular Found (percent): C, 42.9; H, 7.8; N, 4.2; Ag, 34.8. weight=2.4x 106 as in Experiment No. 11 or 12, it is 40 Calc. (percent): C, 42.6; H, 7.7; N, 4.5; Ag, 34.8. clear that typical impurities such as allyl mercaptain or dibutylamine in amounts of the order of 30 p.p.m. will (b) Copper and lead complexes of N-dibutyl halve the attained molecular weight. The tabulated data aminopropane-2-thiol show that with this catalyst the molecular weight can be controlled from below 2000 to about 400,000. The ad These are prepared by the reaction of cupric and lead vantageous step of purifying monomer and catalyst is acetates with the amino thiol, as previously described. demonstrated particularly by the data in Experiments 9, They are viscous oils which can be isolated by extraction 10 and 12 compared with Experiments 8 and 11 with less with ether. pure monomer, and this shows that although theoretical The copper complex is the cupric derivative as shown values have not been obtained molecular weight control by the molecular weight and analytical data. M.wt. is adequate for all practical purposes. (Found 461). M.wt. (Calc. 467). Catalyst, Monomer Calcu (c) Nickel complex of N-dibutylaminopropane-2-thiol Experi- molesfmole purity (a), MW (b) lated ment lOOle percent (CHCl). Obsed ver(c) This is a dark brown viscous oil prepared by reacting

an aqueous solution of NiTI acetate and N-dibutylamino >99.5 ------1,340(d) 1,350 > 99.5 ------3,900(d) 2,200 55 propane-2-thiol. >99.5 0.7 11,000 8,800 Found (percent): C, 58.6; H, 10.8; N, 5.8: Ni, 12.9. >99.5 0.60 46,000 42,000 ca. 97 0.50 38,000 100,000 Calc. (percent); C, 57.1; H, 10.4; N, 6.1; Ni, 12.7. M.wt.: ca. 97 0.54 40,000 150,000 Found 477, Calc. 463. ca. 97 0.72 56,000 200,000 ca. 97 0.83 66,000 1,200,000 These complexes are believed to have the general struc >99.5 18 60,000 1,500,000 - - 5.95X105 (e) >99.5 3.6 380,000 1,200,000 60 ture shown below: ill- 3.0X105 ca. 97 0.88 71,000 2,400,000 12------3.0X105 (e) >99, 5 4.20 420,000 2,400,000 CH-S (a) From gas phase chromatographic examination. Monomer treated with a 2% solution of litharge in 10% CE: bH-N 2 NaOH to remove mercaptain impurities. CAE CHg (b) Obtained from the intrinsic viscosity in CHCl related to molecular weight by n=0.6X 10-4 M0.86 (units, dil./g.). where M=Ag, Cu, Pb or Ni. (c) Molecular weights, measured and calculated refer to The various metal complexes were compared for cata to double molecules since the catalyst is a bifunctional lytic efficiency in the polymerization of propylene sulphide initiator and remains in the polymer (Cd (S polymer and also with the zinc and cadmium complexes of the NBu)2). same thiol, prepared as in Examples I and II. The polym (d) Ebullioscopic molecular weight. erizations were effected at 23° C. using 0.02 mole of (e) Specially purified catalyst, details as follows: 75 catalyst/mole monomer. 3,499,887 O polymer produced, or which may be involved in transfer Polymer Yield, Time, Yield, percent reactions during the polymerization. Complex hrs. percent hr. (a) Cadmium mercaptide of 1,2,3 propane trithiol M-Cd--- 90 90 Zn--- 3 80 27 To cadmium acetate dihydrate (7.6 gm.) in boiling Cu.-- 48 95 2 5 Ag--- 48 80 ... 6 methanol (100 ml.) was added the trithiol (2.8 gm.). Ni--- 60 60 After 2 hours the precipitate was filtered off, washed Pb--- 60 53 0.9 thoroughly with methanol and dried in vacuo. The product was insoluble in common solvents and in propylene sul These results show the greater reactivity of zinc and phide. cadmium compounds compared with the other metal O Analysis.-Found (percent): C, 14.5; H, 2.4; Cd, 46.3; complexes, S, 36.8. EXAMPLE X The analysis corresponds to an empirical formula This example illustrates the polymerization of ethylene C3H6CdS and an argentimetric titration reveals the pres sulphide by the zinc and cadmium complexes of dibutyl 5 ence of one -SH group per cadmium atom. Several struc aminopropane-2-thiol prepared as in Examples I and II. tures are possible but The polymerizations were conducted at 20 C, in the ab CES N sence of Solvent. The catalyst dissolved immediately in Cd the monomer. / CBS Catalyst concentration, 1?olymer yield percent &HSH moleimole ------is probably its simplest monomeric form. mononner 10 20 30 40 Catalyst X9 i hr, hr. hr. hr. (b) Zinc mercaptide of propane 1,2,3 trithiol Zinc------6 9 23 51 78 25 12 20 52 77 92 This was prepared in the same way as the cadmium Cadmium------6 34 65 85 93 analogue replacing the cadmium acetate with hydrated 2 75 93 100 ------Zinc acetate. The analysis corresponded exactly to the formula suggested in the preceding experiment except that In the case of the zinc complex there is an acceleration Zinc was present instead of cadmium. Both these com in the rate as polymerization proceeds up to about 60% 30 plexes were found to be effective catalysts for the polym conversion after which there is a decline in rate as mono erization of alkylene Sulphides, and after removal of mer is consumed. This is due to the reaction of the solu metal the properties of the polymer were found to be ble complex with ethylene sulphide being slower than consistent with their having three thiol groups per the subsequent rate of addition of monomer to the grow molecule. ing polymer chain. The exact behaviour of the catalyst 35 depends on the nature of the complex and the metal and EXAMPLE XII in some cases the maximum rate is observed immediately This example illustrates the preparation of bifunctional and thereafter there is a steady fall in rate as the reaction initiators containing two metal-Sulphur bonds and a proceeds. The induction periods with cadmium catalysts donor atom within the organic grouping and which in are generally very small. 40 their simplest form would have the general structure EXAMPLE X This example describes the preparation of cadmium bis 1-methyl-2-(1'-methyl-2'-diethylamino ethyl thio)- mercaptide), 45 (a) Cadmium mercaptide of N-bis (6-mercapto EtN.CH3CH(CH3)SCHCHCCH) S-Cd ethyl) ethylamine and its use as a catalyst for the polymerization of To a solution of cadmium acetate dihydrate (7.5 gm.) propylene sulphide. in water (45 ml.) and concentrated ammonia (20 mi.) To a stirred solution of cadmium acetate dihydrate (6.6 was added the amino dithiol (4.39 gm.). The mixture was gm.) in boiling methanol (100 ml.) was added the amino shaken vigorously for 1 hour. The white precipitate was thiol (11.0 gm., 0.05 mole) (1,2-dimethyl-2'-diethyl removed and washed thoroughly with distilled water amino-2-mercapto-diethyl sulphide). After 1 hour the until neutral. It was then washed with methanol and solution was cooled and filtered from a small amount of ether and finally dried under high vacuum. The product solid. The filtrate was concentrated in vacuo to afford 55 Was insoluble in common solvents, but rapidly dissolved a viscous oil which, on trituration with ether, yielded the in propylene Sulphide-benzene mixtures and effected rapid white amorphous cadmium mercaptide. This compound is conversion of the propylene sulphide to polymer. an excellent catalyst for episulphide polymerization and (b) Zinc and cadmium mercaptides of N-bis (2- maximum polymerization rate is attained immediately in mercaptopropyl) benzylamine dicating that the insertion of the first monomer unit into 60 the complex occurs at least as fast as the addition of sub These were prepared in a manner similar to that of sequent units. This behaviour is to be contrasted with the preceding experiment. Both were white solids; the Example IX where a slow starting reaction was observed Zinc catalyst was soluble in solvents and in monomer in one instance. By choice of initiator structure induction whereas the cadmium catalyst was essentially insoluble periods are completely eliminated. 65 in solvents and in monomer. EXAMPLE X EXAMPLE XIII This example illustrates the preparation of catalysts This example illustrates that polymerizations of propyl from a polyfunctional trithiol. In addition to the specified ene sulphide with the types of catalysts used in this inven S 70 tion are not retarded or influenced significantly by the M^ Ye presence of water. Catalyst (0.004.8 g. cadmium bis (N- N / di-butylaminopropane-2-mercaptide) prepared as in Ex S ample II unless otherwise stated) was dissolved in 15 cc. structure the R grouping has a free thiol group which of monomer and the mixture stirred end-over-end in a may be useful for conducting further reactions in the 75 capped beverage bottle at room temperature for 72 3,499,887 12 hours. The polymer was isolated by diluting with ben EXAMPLE XVI Zene and freeze drying the solution. The experiment was This example illustrates the preparation of a cadium repeated except that 5 cc. of deionised water was also containing catalyst from a 2-oxo thiol. added to the mixture in a crown-capped bottle. The re To a solution of cadmium acetate dihydrate (14 gm.) action was allowed to proceed under the same condi in boiling methanol (100 ml.) and 0.880 ammonia (10 tions as above and the polymer was isolated in the same ml.) was added 2-(butyloxy) ethyl mercaptain (13.8 gm.). way. It was observed that the products from the two The white precipitate which formed, redissolved almost experiments were identical in molecular weight and immediately. After 30 minutes most of the alcohol was re yield. moved under reduced pressure, and the residue was poured Condition: O into water. The oily layer was extracted with benzene, Anhydrous washed thoroughly with water, and dried with anhydrous Percent yield ------100 magnesium sulphate. The solvent was removed by freeze n-CHCl ...... - - - -as a a es - a r------1.8 drying to leave a resinous solid (93%) having a molecu Aqueous lar weight in benzene of about 4770 and in chloroform of Percent yield ------100 5 about 3820. This shows that in these solvents co-ordina n-CHCls ------1.8 tion of the oxygen with carmium is largely intermolecular, EXAMPLE XIV differing in this respect from the amino complexes such as those described in Example I. This example illustrates the preparation of Zinc and Analysis.--Found (percent): C, 36.6; H, 6.6; S, 15.3; cadmium containing catalysts from ethylene innine-ethyl 20 30.9. Calc. (percent): C, 38.0; H, 6.9; S, 16.9; Cd, ene sulphide reaction products. 29.7. Equimolar proportions of ethylene imine and ethylene ‘(The analytical discrepancies are probably due to sulphide were reacted in chloroform solution (as a 20% traces of cadmium acetate remaining in the product.) This solution) for 16 hours at 15° C. Solvent was removed, compound was an excellent catalyst, showing no induction without heating, at 0.1 mm. Hg to give an oil in quantita 25 period, for the polymerization of episulphides. tive yield. The oil slowly polymerized on standing or on The following Examples XVII and XVIII illustrate attempted distillation. Its properties were consistent with the preparation of catalysts in which the co-ordinating the structure atom is sulphur, present as the thioether linkage. CH2 N 30 EXAMPLE XVII NCH2CH2SH / 2-mercaptoethyl dodecyl sulphide (10.5 gm.) was re C acted with Cd(OAc).2H2O (7 gm.) in methanol (50 but it is believed that some higher molecular Weight ml.) and 0.880 ammonia (18 ml.). The product was self condensation products e.g. 35 isolated as in Example XVI; molecular weight in ben CH2 zene-3240, chloroforms=1050. It proved to be an excel Y CH,CISCII:CHNHCHCHSH lent catalyst for the polymerization of episulphides. Found (percent): C, 52.9; H, 9.3; S, 18.7; Cd, 17.9. diff. Calc. (percent): C, 52.9; H, 9.2; S, 20.0; Cd, 17.7. and cyclic structures were also present. The oil (52 g.) 40 was treated with cadmium acetate dihydrate (75 g.) in EXAMPLE XVIII methanol (200 ml.) and 0.880 ammonia (50 ml.). A mildly exothermic reaction ensued which was completed Cd(OAc).2H2O (13.3 gm.) in methanol (100 ml.) by heating under reflux for 1 hour. Solvent was removed, and 0.880 ammonia (20 ml.) was reacted with 2-mercap the product washed with water and dried under vacuum, toethyl butyl sulphide (15 gm.) in an identical manner The cadmium complex was a solid resinous material 45 to Example XVI. The product was a highly viscous gum which polymerized propylene sulphide in bulk or Solu which was soluble in benzene, but only slightly so in tion rapidly at room temperature. petrol and ether. M.wt. 5930 (benzene), 2960 (chloro Replacing the cadmium acetate by hydrated Zinc ace form). tate (56 g.) in the above preparation gave the Zinc Com Found (percent): C, 34.6; H, 6.3; S, 29.5; Cd, 28.6. plex which was also an effective catalyst for the polym 50 Calc. (percent): C, 35.1; H, 6.3; S, 31.2; Cd, 29.3. erization of propylene sulphide. This complex was found to be an excellent catalyst for the preparation of polymers from episulphides. EXAMPLE XV In both these examples the molecular weight of the This example illustrates the preparation of catalysts complexes in solution were greatly in excess of that of consisting of the zinc or cadmium mercaptide of N,N'- 55 the monomeric compound, showing that (as in the case bis-(6-mercaptoethyl)piperazine. where oxygen is the co-ordinating atom as in Example To a solution of cadmium acetate dihydrate (15gm.), VXI) associated is predominantly intermolecular rather in methanol (100 ml.) was added 0.880 ammonia (15 than intramolecular. ml.) and the dithiol (10.0 gm.). After refluxing for 1 hour Having now described our invention; what we claim is: the precipitate was filtered off, Washed thoroughly with 60 1. A metal mercaptide suitable for use as a catalyst for water, methanol and ether and dried in vacuo. The analy the polymerization of episulphides, said mercaptide being sis of the cadmium complex was C=27.9%; H=4.8%; the reaction product of a reactive compound of a metal N-5.9%; S-12.4%; Cd=36.9% O (by differ selected from zinc, cadmium, silver, copper, nickel and ence)- 12.1%. This analysis showed that in addition lead and a compound selected from the group consisting to the formation of the metal mercaptide, i.e. 65 of N-dibutylaminopropane - 2 - thiol and N-monobutyl aminopropane-2-thiol. Yc.H. 2. A metal mercaptide suitable for use as a catalyst N / ) for the polymerization of episulphides, said mercaptide SCHN O being the reaction product of a reactive compound of a or polymeric structures of the same empirical formula, metal selected from zinc, cadmium, silver, copper, nickel additional cadmium acetate was complexed to the nitrogen and lead and N-bis (beta-mercaptoethyl) ethylamine. atoms. 3. A metal mercaptide suitable for use as a catalyst Similar results were obtained using hydrated Zinc ace for the polymerization of episulphides, said mercaptide tate (11.5 gm.) instead of the cadmium acetate. 75 being the reaction product of a reactive compound of a 3,499,887 3. 4. metal selected from zinc, cadmium, silver, copper, nickel FOREIGN PATENTS and lead and N-bis (2-mercaptopropyl) benzylamine. 4. A metal mercaptide suitable for use as a catalyst 1,211,626 3/1966 Germany. for the polymerization of episulphides, said mercaptide being the reaction product of a reactive compound of a OTHER REFERENCES metal selected from zinc, cadmium, silver, copper, nickel Epstein et al., Inorg. Chem., 4 (1965) pp. 1551-2. and lead and a substituted organic amine having a re Leussing et al., J. Am. Chem. (Soc. 82 (1960) pp. active thiol group and having the formula 4858-9. Neville et al., J. Am. Chem. Soc., 78 (1965) p. 4895. R5 (Ra)N-R-SH Vasil'eva et al., Chem. Abst., 54 (1960) col. 24370. wherein Riis-CH2CH2- or Schwarzenbach, Chem. Abst., 63 (1965) col. 5673. Hein et al., Z. Anorg. Allgem. Chemie, 308 (1961) -CH2CH2S.CH2CH2.NH.CHCH pp. 133-9. and R5 and R4 jointly form a group selected from Tanaka et al., Chem. Pharm. Bull (Tokyo) 10 (1962) -CH2CH pp. 18, 23, 30. and -CH2CH2.N(CH2CH2SH).CH2CH-. TOBIASE. LEVOW, Primary Examiner References Cited A. P. DEMERS, Assistant Examiner UNITED STATES PATENTS U.S. C. X.R. 2,038,486 4/1936 Glas ------204-1 252-431; 260-79.7, 242, 268, 429, 429.9, 438.1, 430, 2,855,418 10/1958 Mugnier ------260-429 435, 439,570.9,583, 607 2,976,122 3/1961 Ertelt et al. ------23-230 3,027,239 3/1962 Clark ------23-230