Use of organophosphorus(V) sulfides for the modification of propene polymerization catalysts

Abstract

AbstractStudies of various organophosphorus(V) sulfides, including esters of thiophosphoric acid and triorganophosphine sulfides, were evaluated as propene polymerization catalyst modifiers. Among these, triethyl thiophosphate (1a) leads to the best activity‐stereospecificity combinations. Higher alkyl or aryl esters of thiophosphoric acid lead to higher catalyst activities but significantly poorer stereospecificities, relative to 1a, while the latter modifier is advantageous over triaryl‐ or tris(diakylamino)phosphorus sulfides, as far as both activity and stereospecificity are concerned. Organophosphorus(V) sulfides appear to be better modifiers in general than the corresponding oxides. No straightforward correlations of the modifying effects of the preceding compounds to the inductive and steric effects of the substituents on phosphorus were possible, as some of these compounds (namely the thiophosphoryl or phosphoryl alkyl esters) may undergo dealkylation reactions with the components of the catalyst system, yielding alkyl chloride, traces of HCl and alkene, and polymeric metal (Ti3+ or Al3+) complexes with anionic R2POS− ligands. A number of binary modifier (1a plus an additional modifier) packages with attractive performance characteristics were developed. Evaluations of these systems in 2 h bulk propylene polymerizations showed that use of triphenylantimony oxide (8) as additional modifier leads to the best overall catalyst performance (yield: 2636 g/g AA TiCl3; hexane extractables: 0,80%). With the 1a‐collidine (9) modifier package, comparable stereospecificity but substantially lower catalyst activity were realized, while use of bis(tributylin) sulfide (6), tributyl phosphite (7) or 2,5‐dimethyltetrahydrofuran (10) as additional modifiers led to good yields (2650–3000 g/g AA TiCl3) but more than double (1,70–2,00%) the hexane extractables, relative to the 1a–8 modifier system.